ORCID Profile
0000-0001-6341-4364
Current Organisation
University of Melbourne
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Organic Chemical Synthesis | Biological And Medical Chemistry | Organic Chemistry | Medicinal and Biomolecular Chemistry | Biologically Active Molecules | Cell Metabolism | Synthesis of Materials | Structural Chemistry | Physical Chemistry of Materials | Optical Properties of Materials | Analytical Spectrometry | Characterisation Of Macromolecules | Nanochemistry and Supramolecular Chemistry | Chemical Characterisation of Materials | Physical Organic Chemistry | Sociology and Social Studies of Science and Technology | Clinical Pharmacology And Therapeutics | Analytical Biochemistry | Enzymes | Analytical Chemistry | Analytical Spectrometry | Main Group Metal Chemistry | Separation Science | Transition Metal Chemistry | Macromolecular and Materials Chemistry | Inorganic Chemistry | Solid State Chemistry | Bioinorganic Chemistry | Cardiology (Incl. Cardiovascular Diseases) | Flow Analysis | Physical Chemistry (Incl. Structural) | F-Block Chemistry | Structural Chemistry and Spectroscopy | Cellular Interactions (incl. Adhesion, Matrix, Cell Wall) | Cell Metabolism
ANZSRC Socio-Economic Objective (SEO)
Treatments (e.g. chemicals, antibiotics) | Expanding Knowledge in the Chemical Sciences | Immune System and Allergy | Human Pharmaceutical Treatments (e.g. Antibiotics) | Chemical sciences | Cancer and Related Disorders | Environmentally Sustainable Plant Production not elsewhere classified | Infectious diseases | Chemical Fertilisers | Primary products from plants | Organic Industrial Chemicals (excl. Resins, Rubber and Plastics) | Agricultural chemicals not elsewhere classified | Environmentally Sustainable Manufacturing not elsewhere classified | Control of pests and exotic species | Infectious Diseases | Prevention and treatment of pollution | Other | Workforce Transition and Employment | Crop Protection Chemicals | Cardiovascular system and diseases | Medical instrumentation | Manufacturing not elsewhere classified | Inherited diseases (incl. gene therapy) | Biofuel (Biomass) Energy | Expanding Knowledge in the Biological Sciences | Prevention—biologicals (e.g. vaccines) |
Related Links
Publications
Oxidative desulfurization pathway for complete catabolism of sulfoquinovose by bacteria
Publisher: Proceedings of the National Academy of Sciences
Date: 24-01-2022
Abstract: Sulfoquinovose, a sulfosugar derivative of glucose, is produced by most photosynthetic organisms and contains up to half of all sulfur in the biosphere. Several pathways for its breakdown are known, though they provide access to only half of the carbon in sulfoquinovose and none of its sulfur. Here, we describe a fundamentally different pathway within the plant pathogen Agrobacterium tumefaciens that features oxidative desulfurization of sulfoquinovose to access all carbon and sulfur within the molecule. Biochemical and structural analyses of the pathway’s key proteins provided insights how the sulfosugar is recognized and degraded. Genes encoding this sulfoquinovose monooxygenase pathway are present in many plant pathogens and symbionts, alluding to a possible role for sulfoquinovose in plant host–bacteria interactions.
From the banal to the bizarre: unravelling immune recognition and response to microbial lipids
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1CC06003A
Abstract: This account reviews the total synthesis of immune active lipidic species and their activity through lipid-sensing receptor and cell-mediated immunity.
Sulfotransferases, sulfatases and formylglycine-generating enzymes: a sulfation fascination
Publisher: Elsevier BV
Date: 10-2008
DOI: 10.1016/J.CBPA.2008.06.018
Abstract: Sulfotransferases and sulfatases are the major enzymes responsible for sulfate transfer processes. The past two years have seen the elucidation of new functions for these enzymes, and a great progression in their structural characterization, which confirms that these two types of enzymes possess a highly conserved fold. For catalytic activity, sulfatases must contain a formylglycine residue, which is generated by various formylglycine-generating enzymes. Mechanistic and structural details have recently been obtained for a group of cofactor-independent formylglycine-generating enzymes termed FGEs. Finally, an increasing light has been cast upon the mechanism of sulfatase inactivation by a group of clinically important agents, the aryl sulfamates.
Anomeric Anhydro Sugars
Publisher: Springer Berlin Heidelberg
Date: 2001
Glycoprotein misfolding in the endoplasmic reticulum: Identification of released oligosaccharides reveals a second ER-associated degradation pathway for Golgi-retrieved proteins
Publisher: Springer Science and Business Media LLC
Date: 16-03-2013
DOI: 10.1007/S00018-013-1304-6
Abstract: Endoplasmic reticulum-associated degradation (ERAD) is a key cellular process whereby misfolded proteins are removed from the endoplasmic reticulum (ER) for subsequent degradation by the ubiquitin roteasome system. In the present work, analysis of the released, free oligosaccharides (FOS) derived from all glycoproteins undergoing ERAD, has allowed a global estimation of the mechanisms of this pathway rather than following model proteins through degradative routes. Examining the FOS produced in endomannosidase-compromised cells following α-glucosidase inhibition has revealed a mechanism for clearing Golgi-retrieved glycoproteins that have failed to enter the ER quality control cycle. The Glc3Man7GlcNAc2 FOS species has been shown to be produced in the ER lumen by a mechanism involving a peptide: N-glycanase-like activity, and its production was sensitive to disruption of Golgi-ER trafficking. The detection of this oligosaccharide was unaffected by the overexpression of EDEM1 or cytosolic mannosidase, both of which increased the production of previously characterised cytosolically localised FOS. The lumenal FOS identified are therefore distinct in their production and regulation compared to FOS produced by the conventional route of misfolded glycoproteins directly removed from the ER. The production of such lumenal FOS is indicative of a novel degradative route for cellular glycoproteins that may exist under certain conditions.
Crosshole seismic tomography including the anisotropy effect
Publisher: Oxford University Press (OUP)
Date: 28-04-2011
A Sulfoglycolytic Entner-Doudoroff Pathway in Rhizobium leguminosarum bv. trifolii SRDI565
Publisher: American Society for Microbiology
Date: 20-07-2020
DOI: 10.1128/AEM.00750-20
Abstract: Sulfonate sulfur is a major form of organic sulfur in soils but requires biomineralization before it can be utilized by plants. Very little is known about the biochemical processes used to mobilize sulfonate sulfur. We show that a rhizobial isolate from soil, Rhizobium leguminosarum SRDI565, possesses the ability to degrade the abundant phototroph-derived carbohydrate sulfonate SQ through a sulfoglycolytic Entner-Doudoroff pathway. Proteomics and metabolomics demonstrated the utilization of this pathway during growth on SQ and provided evidence for gluconeogenesis. Unexpectedly, off-cycle sulfoglycolytic species were also detected, pointing to the complexity of metabolic processes within cells under conditions of sulfoglycolysis. Thus, rhizobial metabolism of the abundant sulfosugar SQ may contribute to persistence of the bacteria in the soil and to mobilization of sulfur in the pedosphere.
Understanding the cardioprotective effects of flavonols: Discovery of relaxant flavonols without antioxidant activity
Publisher: American Chemical Society (ACS)
Date: 29-02-2008
DOI: 10.1021/JM070352H
Abstract: 3',4'-Dihydroxyflavonol (DiOHF) is a cardioprotective flavonol that can reduce injury after myocardial ischemia and reperfusion and thus is a promising small molecule for the treatment of cardiovascular disease. Like all vasoactive flavonols reported to date, DiOHF is both relaxant and antioxidant, hindering investigation of the relative contribution of each activity for the prevention of reperfusion injury. This study investigates structure-activity relationships of variations at the 3' and 4' positions of the B ring of DiOHF and vasorelaxant and antioxidant activities. Relaxation of rat isolated aortic rings precontracted with KCl revealed that the most active flavonols were those with a 4'-hydroxyl group, with the opening of potassium channels as a possible contributing mechanism. For the antioxidant activity, with the exception of DiOHF, none of the flavonols investigated were able to significantly scavenge superoxide radical, and none of the three most potent vasorelaxant flavonols could prevent oxidant-induced endothelial dysfunction. The discovery of single-acting vasorelaxant flavonols without antioxidant activity, in particular 4'-hydroxy-3'-methoxyflavonol, will assist in investigating the mechanism of flavonol-induced cardioprotection.
Bacterial β-Glucosidase Reveals the Structural and Functional Basis of Genetic Defects in Human Glucocerebrosidase 2 (GBA2)
Publisher: American Chemical Society (ACS)
Date: 06-05-2016
2,6-Disubstituted Benzoates As Neighboring Groups for Enhanced Diastereoselectivity in β-Galactosylation Reactions: Synthesis of β-1,3-Linked Oligogalactosides Related to Arabinogalactan Proteins
Publisher: American Chemical Society (ACS)
Date: 20-11-2009
DOI: 10.1021/JO902100Q
Abstract: Arabinogalactan proteins (AGPs) are plant glycoproteins which contain a beta-1,3-linked galactan core. The synthesis of the beta-galactopyranose-1,3-beta-galactopyranose linkage using various 2-O-acyl-protected glycosyl donors has been plagued with poor stereoselectivity and side reactions including orthoester formation and transesterification of the 2-O-acyl group from the donor to the acceptor. We have investigated the use of 2,6-disubstituted benzoyl groups as bulky neighboring groups on the glycosyl donor. A 2,4,6-trimethylbenzoyl group was found to be optimal and enabled the formation of the beta-galactopyranose-1,3-beta-galactopyranose linkage to disarmed ester-protected acceptors, suppressing transesterification and reducing orthoester formation while enhancing the beta-selectivity of galactosylation reactions. A series of beta-1,3-linked oligogalactosides were prepared and elaborated to neoglycoconjugates for the study of AGP biosynthesis and AGP binding proteins.
Galanin-3 receptor antagonism by SNAP 37889 reduces motivation to self-administer alcohol and attenuates cue-induced reinstatement of alcohol-seeking in iP rats
Publisher: Japanese Pharmacological Society
Date: 2014
DOI: 10.1254/JPHS.13221FP
Abstract: The neuropeptide galanin has a role in promoting alcohol consumption and general feeding behavior. The galanin-3 receptor (GALR3) subtype is implicated in modulating the consumption of alcohol and has therefore been identified as a potential target for new pharmacotherapies to treat alcohol use disorders. We have previously shown that the selective GALR3 antagonist SNAP 37889 reduced voluntary alcohol consumption in iP (alcohol-preferring) rats. The present study firstly aimed to investigate the effect of GALR3 antagonism on the motivational properties of alcohol. Secondly, the potential of GALR3 as a therapeutic target in the prevention of relapse was investigated in response to alcohol-conditioned cues. Administration of SNAP 37889 (30 mg/kg, i.p.) significantly reduced the breakpoint for ethanol under a progressive-ratio operant responding schedule of reinforcement. SNAP 37889 also significantly reduced reinstatement of alcohol-seeking in response to re-exposure to conditioned cues that were previously associated with the availability of alcohol. Collectively, results from the current study provide new evidence of GALR3 involvement in cue-induced relapse and provide further evidence that GALR3 antagonism reduces the motivational drive to consume alcohol. These findings validate further research in to the potential use of SNAP 37889 and other GALR3 antagonists to treat alcohol abuse disorders in humans.
Formation of sugar radical cations from collision-induced dissociation of non-covalent complexes with S-nitroso thiyl radical precursors
Publisher: Elsevier BV
Date: 02-2015
Computational Design of Experiment Unveils the Conformational Reaction Coordinate of GH125 α-Mannosidases
Publisher: American Chemical Society (ACS)
Date: 03-01-2017
DOI: 10.1021/JACS.6B11247
Abstract: Conformational analysis of enzyme-catalyzed mannoside hydrolysis has revealed two predominant conformational itineraries through B
A Purpose-Synthesised Anti-Fibrotic Agent Attenuates Experimental Kidney Diseases in the Rat
Publisher: Public Library of Science (PLoS)
Date: 10-10-2012
Genome sequences of Arthrobacter spp. that use a modified sulfoglycolytic Embden–Meyerhof–Parnas pathway
Publisher: Springer Science and Business Media LLC
Date: 24-02-2022
DOI: 10.1007/S00203-022-02803-2
Abstract: Sulfoglycolysis pathways enable the breakdown of the sulfosugar sulfoquinovose and environmental recycling of its carbon and sulfur content. The prototypical sulfoglycolytic pathway is a variant of the classical Embden–Meyerhof–Parnas (EMP) pathway that results in formation of 2,3-dihydroxypropanesulfonate and was first described in gram-negative Escherichia coli . We used enrichment cultures to discover new sulfoglycolytic bacteria from Australian soil s les. Two gram-positive Arthrobacter spp. were isolated that produced sulfolactate as the metabolic end-product. Genome sequences identified a modified sulfoglycolytic EMP gene cluster, conserved across a range of other Actinobacteria, that retained the core sulfoglycolysis genes encoding metabolic enzymes but featured the replacement of the gene encoding sulfolactaldehyde (SLA) reductase with SLA dehydrogenase, and the absence of sulfoquinovosidase and sulfoquinovose mutarotase genes. Excretion of sulfolactate by these Arthrobacter spp. is consistent with an aerobic saprophytic lifestyle. This work broadens our knowledge of the sulfo-EMP pathway to include soil bacteria.
Detailed Structural Analysis of Glycosidase/Inhibitor Interactions: Complexes of Cex from Cellulomonas fimi with Xylobiose-Derived Aza-Sugars,
Publisher: American Chemical Society (ACS)
Date: 31-08-2000
DOI: 10.1021/BI0010625
Abstract: Detailed insights into the mode of binding of a series of tight-binding aza-sugar glycosidase inhibitors of two fundamentally different classes are described through X-ray crystallographic studies of complexes with the retaining family 10 xylanase Cex from Cellulomonas fimi. Complexes with xylobiose-derived aza-sugar inhibitors of the substituted "amidine" class (xylobio-imidazole, K(i) = 150 nM xylobio-lactam oxime, K(i) = 370 nM) reveal lateral interaction of the "glycosidic" nitrogen with the acid/base catalyst (Glu127) and hydrogen bonding of the sugar 2-hydroxyl with the catalytic nucleophile (Glu233), as expected. Tight binding of xylobio-isofagomine (K(i) = 130 nM) appears to be a consequence of strong interactions of the ring nitrogen with the catalytic nucleophile while, surprisingly, no direct protein contacts are made with the ring nitrogen of the xylobio-deoxynojirimycin analogue (K(i) = 5800 nM). Instead the nitrogen interacts with two ordered water molecules, thereby accounting for its relatively weaker binding, though it still binds some 1200-fold more tightly than does xylobiose, presumably as a consequence of electrostatic interactions at the active site. Dramatically weaker binding of these same inhibitors to the family 11 xylanase Bcx from Bacillus circulans (K(i) from 0.5 to 1.5 mM) is rationalized for the substituted amidines on the basis that this enzyme utilizes a syn protonation trajectory and likely hydrolyzes via a (2,5)B boat transition state. Weaker binding of the deoxynojirimycin and isofagomine analogues likely reflects the energetic penalty for distortion of these analogues to a (2,5)B conformation, possibly coupled with destabilizing interactions with Tyr69, a conserved, catalytically essential active site residue.
Structural and mechanistic insights into a Bacteroides vulgatus retaining N-acetyl-β-galactosaminidase that uses neighbouring group participation
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CC04649E
Abstract: Bv GH123 catalyzes cleavage with retention of anomeric configuration structural analysis of a mimic of a putative oxazolinium ion intermediate supports a neighbouring group participation mechanism.
Trehalose Is Required for Growth of Mycobacterium smegmatis
Publisher: Elsevier BV
Date: 07-2004
Synthetic β-1,2-Mannosyloxymannitol Glycolipid from the Fungus Malassezia pachydermatis Signals through Human Mincle
Publisher: American Chemical Society (ACS)
Date: 03-05-2019
Abstract: Mincle is a C-type lectin receptor of the innate immune system with the ability to sense pathogens and commensals through lipidic metabolites. While a growing number of bacterial glycolipids have been discovered that can signal through human Mincle, no fungal metabolites are known that can signal through the human form of this receptor. We report the total synthesis of a complex β-1,2-mannosyloxymannitol glycolipid from Malassezia pachydermatis 44-2, which was reported to signal through the murine Mincle receptor. Assembly of 44-2 was achieved through a highly convergent route that exploits symmetry elements inherent within this molecule and delineation of conditions that maintain the delicate l-mannitol triester-triol array. We show that 44-2 is a potent agonist of human Mincle signaling and constitutes the first fungal metabolite identified that can signal through the human Mincle receptor, providing new insights into antifungal immunity.
High-Resolution Crystal Structures of the Lectin-like Xylan Binding Domain from Streptomyces lividans Xylanase 10A with Bound Substrates Reveal a Novel Mode of Xylan Binding,
Publisher: American Chemical Society (ACS)
Date: 09-03-2002
DOI: 10.1021/BI015865J
Abstract: Carbohydrate-binding module (CBM) family 13 includes the "R-type" or "ricin superfamily" beta-trefoil lectins. The C-terminal CBM, CBM13, of xylanase 10A from Streptomyces lividans is a family 13 CBM that is not only structurally similar to the "R-type" lectins but also somewhat functionally similar. The primary function of CBM13 is to bind the polysaccharide xylan, but it retains the ability of the R-type lectins to bind small sugars such as lactose and galactose. The association of CBM13 with xylan appears to involve cooperative and additive participation of three binding pockets in each of the three trefoil domains of CBM13, suggesting a novel mechanism of CBM-xylan interaction. Thus, the interaction of CBM13 with sugars displays considerable plasticity for which we provide a structural rationale. The high-resolution crystal structure of CBM13 was determined by multiple anomalous dispersion from a complex of CBM13 with a brominated ligand. Crystal structures of CBM13 in complex with lactose and xylopentaose revealed two distinct mechanisms of ligand binding. CBM13 has retained its specificity for lactose via Ricin-like binding in all of the three classic trefoil binding pockets. However, CBM13 has the ability to bind either the nonreducing galactosyl moiety or the reducing glucosyl moiety of lactose. The mode of xylopentaose binding suggests adaptive mutations in the trefoil sugar binding scaffold to accommodate internal binding on helical polymers of xylose.
2-Morpholinoisoflav-3-enes as flexible intermediates in the synthesis of phenoxodiol, isophenoxodiol, equol and analogues: Vasorelaxant properties, estrogen receptor binding and Rho/RhoA kinase pathway inhibition
Publisher: Elsevier BV
Date: 04-2012
DOI: 10.1016/J.BMC.2012.02.008
Abstract: Isoflavone consumption correlates with reduced rates of cardiovascular disease. Epidemiological studies and clinical data provide evidence that isoflavone metabolites, such as the isoflavan equol, contribute to these beneficial effects. In this study we developed a new route to isoflavans and isoflavenes via 2-morpholinoisoflavenes derived from a condensation reaction of phenylacetaldehydes, salicylaldehydes and morpholine. We report the synthesis of the isoflavans equol and deoxygenated analogues, and the isoflavenes 7,4'-dihydroxyisoflav-3-ene (phenoxodiol, haganin E) and 7,4'-dihydroxyisoflav-2-ene (isophenoxodiol). Vascular pharmacology studies reveal that all oxygenated isoflavans and isoflavenes can attenuate phenylephrine-induced vasoconstriction, which was unaffected by the estrogen receptor antagonist ICI 182,780. Furthermore, the compounds inhibited U46619 (a thromboxane A(2) analogue) induced vasoconstriction in endothelium-denuded rat aortae, and reduced the formation of GTP RhoA, with the effects being greatest for equol and phenoxodiol. Ligand displacement studies of rat uterine cytosol estrogen receptor revealed the compounds to be generally weak binders. These data are consistent with the vasorelaxation activity of equol and phenoxodiol deriving at least in part by inhibition of the RhoA/Rho-kinase pathway, and along with the limited estrogen receptor affinity supports a role for equol and phenoxodiol as useful agents for maintaining cardiovascular function with limited estrogenic effects.
Defining the molecular architecture, metal dependence, and distribution of metal-dependent class II sulfofructose-1-phosphate aldolases
Publisher: Elsevier BV
Date: 10-2023
Sulfotransferases and Sulfatases in Mycobacteria
Publisher: Elsevier BV
Date: 07-2002
DOI: 10.1016/S1074-5521(02)00175-8
Abstract: Analysis of the genomes of M. tuberculosis, M. leprae, M. smegmatis, and M. avium has revealed a large family of genes homologous to known sulfotransferases. Despite reports detailing a suite of sulfated glycolipids in many mycobacteria, a corresponding family of sulfotransferase genes remains uncharacterized. Here, a sequence-based analysis of newly discovered mycobacterial sulfotransferase genes, named stf1-stf10, is presented. Interestingly, two sulfotransferase genes are highly similar to mammalian sulfotransferases, increasing the list of mycobacterial eukaryotic-like protein families. The sulfotransferases join an equally complex family of mycobacterial sulfatases: a large family of sulfatase genes has been found in all of the mycobacterial genomes examined. As sulfated molecules are common mediators of cell-cell interactions, the sulfotransferases and sulfatases may be involved in regulating host-pathogen interactions.
Dynamic Structural Changes Accompany the Production of 2-Dihydroxypropanesulfonate by Sulfolactaldehyde Reductase
Publisher: American Chemical Society (ACS)
Date: 22-10-2019
DOI: 10.26434/CHEMRXIV.9725120
Abstract: 2,3-Dihydroxypropanesulfonate (DHPS) is a major sulfur species in the biosphere. One important route for the production of DHPS includes sulfoglycolytic catabolism of sulfoquinovose (SQ) through the Embden-Meyerhof-Parnas (sulfo-EMP) pathway. SQ is a sulfonated carbohydrate present in plant and cyanobacterial sulfolipids (sulfoquinovosyl diacylglyceride and its metabolites) and is biosynthesised globally at a rate of around 10 billion tonnes per annum. The final step in the bacterial sulfo-EMP pathway involves reduction of sulfolactaldehyde (SLA) to DHPS, catalysed by an NADH-dependent SLA reductase. On the basis of conserved sequence motifs, we assign SLA reductase to the β-hydroxyacid dehydrogenase (β-HAD) family, making it the first ex le of a β-HAD enzyme that acts on a sulfonic acid, rather than a carboxylic acid substrate. We report crystal structures of the SLA reductase YihU from E. coli K-12 in its apo and cofactor-bound states, as well as the ternary complex YihU•NADH•DHPS with the cofactor and product bound in the active site. Conformational flexibility observed in these structures, combined with kinetic studies, confirm a sequential mechanism and provide evidence for dynamic domain movements that occur during catalysis. The ternary complex structure reveals a conserved sulfonate pocket in SLA reductase that recognises the sulfonate oxygens through hydrogen bonding to Asn174, Ser178, and the backbone amide of Arg123, along with an ordered water molecule. This triad of residues distinguishes these enzymes from classical β-HADs that act on carboxylate substrates. A comparison of YihU crystal structures with close structural homologues within the β-HAD family highlights key differences in the overall domain organization and identifies a unique peptide sequence that is predictive of SLA reductase activity. br
A building block approach to the synthesis of a family of S-linked α-1,6-oligomannosides
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.CARRES.2016.04.015
Abstract: The syntheses of α-1,6-S-linked methyl di-, tetra- and hexamannosides are reported. The sulfur linkages are generated through coupling of thiolates (derived from anomeric thioacetates or isothiouronium bromides) with 6-deoxy-6-iodo sugars. Two approaches are detailed that involve [2 + 2 + 2] construction from either the reducing end or the non-reducing end. In constructing from the reducing end, coupling of a disaccharide thioacetate with a 6'-iodo reducing end disaccharide, followed by activation of the resulting tetrasaccharide to a 6'''-iodide, and iterative coupling with the same disaccharide thioacetate afforded the S-linked hexasaccharide, as well as the intermediate di- and tetrasaccharides. On the other hand, construction from the non-reducing end involved coupling of the above disaccharide thioacetate with an anomeric S-trityl protected 6'-iodo disaccharide. The resulting S-trityl tetrasaccharide was converted to a tetrasaccharide thioacetate, which was coupled with the same anomeric S-trityl protected 6'-iodo disaccharide to afford the hexasaccharide, which was elaborated to the methyl thioglycoside. The developed methodology may prove useful for the construction of other S-linked oligosaccharides.
Glycolipids from the gut symbiont Bacteroides fragilis are agonists for natural killer T cells and induce their regulatory differentiation
Publisher: American Chemical Society (ACS)
Date: 25-04-2023
DOI: 10.26434/CHEMRXIV-2023-XBJD0
Abstract: Natural Killer T (NKT) cells are a lipid-antigen reactive, CD1d-restricted T cell subset with erse functional properties that contribute to inflammatory and regulatory immune responses. The most studied lipid antigen target for these cells is alpha-galactosylceramide (GC). The commensal organism Bacteroides fragilis (B. fragilis) produces several forms of GC, but conflicting information exists about the influence of these lipids on NKT cells. Herein, we report the total synthesis of a major form of alpha-GC from B. fragilis (Bf alpha-GC), and several analogues thereof. We confirm the T cell receptor (TCR)-mediated recognition of these glycolipids by mouse and human NKT cells. Despite the natural structure of Bf alpha-GC containing lipid branching that limits potency, we demonstrate that Bf alpha-GC drives mouse NKT cells to proliferate and differentiate into producers of the immunoregulatory cytokine, interleukin-10 (IL-10). These Bf alpha-GC-experienced NKT cells display regulatory function by inhibiting the expansion of naïve NKT cells upon subsequent exposure to this antigen. Moreover, this regulatory activity impacts more than just NKT cells, as demonstrated by the NKT cell-mediated inhibition of antigen-stimulated mucosal-associated invariant T (MAIT) cells. These findings reveal that B. fragilis-derived NKT cell agonists may have broad immunoregulatory activity, providing insight into the mechanisms influencing immune tolerance to commensal bacteria and highlighting a potential means to manipulate NKT cell function for therapeutic benefit.
Robert Vyent Stick: A Colourful Character
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/CH09047
A single glycosidase harnesses different pyranoside ring transition state conformations for hydrolysis of mannosides and glucosides
Publisher: American Chemical Society (ACS)
Date: 11-09-2015
Localization of Oleuropeyl Glucose Esters and a Flavanone to Secretory Cavities of Myrtaceae
Publisher: Public Library of Science (PLoS)
Date: 20-07-2012
Synthesis of glycosyl fluorides from thio-, seleno-, and telluroglycosides and glycosyl sulfoxides using aminodifluorosulfinium tetrafluoroborates
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.CARRES.2012.04.016
Abstract: Glycosyl fluorides can be synthesized from thio-, seleno-, and telluroglycosides and glycosyl sulfoxides using the aminodifluorosulfinium tetrafluoroborate reagents Xtalfluor-E and -M, with or without added N-bromosuccinimide. Mechanistic studies provide evidence that fluoride is delivered from the tetrafluoroborate counterion.
Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan
Publisher: Beilstein Institut
Date: 28-03-2011
DOI: 10.3762/BJOC.7.47
Abstract: Mycobacterium tuberculosis , the causitive agent of tuberculosis (TB), possesses a complex cell wall containing mannose-rich glycophospholids termed phosphatidylinositol mannosides (PIMs), lipomannan (LM), and lipoarabinomannan (LAM). These glycophospholipids play important roles in cell wall function and host–pathogen interactions. Synthetic PIM/LM/LAM substructures are useful biochemical tools to delineate and dissect the fine details of mannose glycophospholipid biosynthesis and their interactions with host cells. We report the efficient synthesis of a series of azidooctyl di- and trimannosides possessing the following glycan structures: α-Man-1,6-α-Man, α-Man-1,6-α-Man-1,6-α-Man, α-Man-1,2-α-Man-1,6-α-Man and 2,6-di-(α-Man)-α-Man. The synthesis includes the use of non-benzyl protecting groups compatible with the azido group and preparation of the branched trisaccharide structure 2,6-di-(α-Man)-α-Man through a double glycosylation of a 3,4-butanediacetal-protected mannoside. The azidooctyl groups of these synthetic mannans were elaborated to fluorescent glycoconjugates and squaric ester derivatives useful for further conjugation studies.
A twin study of polycystic ovary syndrome
Publisher: Elsevier BV
Date: 03-1995
Antioxidant activity contributes to flavonol cardioprotection during reperfusion of rat hearts
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.FREERADBIOMED.2011.07.003
Abstract: The mechanism of flavonol-induced cardioprotection is unclear. We compared the protective actions of a flavonol that inhibits calcium utilization and has antioxidant activity, 3',4'-dihydroxyflavonol (DiOHF) a flavonol that affects only calcium activity, 4'-OH-3'-OCH(3)-flavonol (4'-OH-3'-OCH(3)F) and a water-soluble flavonol with selective antioxidant activity, DiOHF-6-succinamic acid (DiOHF-6-SA), in isolated, perfused rat hearts. Hearts were subjected to global ischemia for 20 min followed by 30 min reperfusion and were treated with vehicle (0.05% DMSO), DiOHF, 4'-OH-3'-OCH(3)F, or DiOHF-6-SA (all 10 μM, n=5-8 per group). Flavonols were infused for 10 min before ischemia and during reperfusion. In vehicle-treated hearts, left-ventricular (LV) +dP/dt was reduced by 60% at the end of reperfusion compared to the preischemic level. Lactate dehydrogenase (LDH) release was elevated and endothelial NO synthase (eNOS) expression was lower in vehicle-treated hearts compared to shams. In comparison, DiOHF treatment improved LV function upon reperfusion, decreased LDH, and preserved eNOS expression. The antioxidant DiOHF-6-SA also preserved contractility, reduced LDH, and preserved eNOS expression. In contrast, hearts treated with 4'-OH-3'-OCH(3)F showed a degree of contractile impairment similar to that of the vehicle group. DiOHF and DiOHF-6-SA also exerted cardioprotection when given only during reperfusion and not when administered only before ischemia. Flavonol-induced cardioprotection relies on antioxidant activity and is mainly exerted during reperfusion.
Dynamic Structural Changes Accompany the Production of 2-Dihydroxypropanesulfonate by Sulfolactaldehyde Reductase
Publisher: American Chemical Society (ACS)
Date: 26-08-2019
DOI: 10.26434/CHEMRXIV.9725120.V1
Abstract: 2,3-Dihydroxypropanesulfonate (DHPS) is a major sulfur species in the biosphere. One important route for the production of DHPS includes sulfoglycolytic catabolism of sulfoquinovose (SQ) through the Embden-Meyerhof-Parnas (sulfo-EMP) pathway. SQ is a sulfonated carbohydrate present in plant and cyanobacterial sulfolipids (sulfoquinovosyl diacylglyceride and its metabolites) and is biosynthesised globally at a rate of around 10 billion tonnes per annum. The final step in the bacterial sulfo-EMP pathway involves reduction of sulfolactaldehyde (SLA) to DHPS, catalysed by an NADH-dependent SLA reductase. On the basis of conserved sequence motifs, we assign SLA reductase to the β-hydroxyacid dehydrogenase (β-HAD) family, making it the first ex le of a β-HAD enzyme that acts on a sulfonic acid, rather than a carboxylic acid substrate. We report crystal structures of the SLA reductase YihU from E. coli K-12 in its apo and cofactor-bound states, as well as the ternary complex YihU•NADH•DHPS with the cofactor and product bound in the active site. Conformational flexibility observed in these structures, combined with kinetic studies, confirm a sequential mechanism and provide evidence for dynamic domain movements that occur during catalysis. The ternary complex structure reveals a conserved sulfonate pocket in SLA reductase that recognises the sulfonate oxygens through hydrogen bonding to Asn174, Ser178, and the backbone amide of Arg123, along with an ordered water molecule. This triad of residues distinguishes these enzymes from classical β-HADs that act on carboxylate substrates. A comparison of YihU crystal structures with close structural homologues within the β-HAD family highlights key differences in the overall domain organization and identifies a unique peptide sequence that is predictive of SLA reductase activity.
Mycobacterium tuberculosis β-gentiobiosyl diacylglycerides signal through the pattern recognition receptor Mincle: total synthesis and structure activity relationships
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5CC04773K
Abstract: Gentiobiosyl diglycerides from Mycobacterium tuberculosis are shown to signal through Mincle structure–activity relationships reveal analogues with enhanced potency.
Contribution of Shape and Charge to the Inhibition of a Family GH99 endo-α-1,2-Mannanase
Publisher: American Chemical Society (ACS)
Date: 17-01-2017
DOI: 10.1021/JACS.6B10075
α-Glucuronosyl and α-glucosyl diacylglycerides, natural killer T cell-activating lipids from bacteria and fungi
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9SC05248H
Abstract: Microbial α-glycosyl diacylglycerides when presented by the antigen presenting molecule CD1d are recognized by both classical type I and atypical Natural Killer T cell receptors.
Dynamic Structural Changes Accompany the Production of 2-Dihydroxypropanesulfonate by Sulfolactaldehyde Reductase
Publisher: American Chemical Society (ACS)
Date: 22-10-2019
DOI: 10.26434/CHEMRXIV.9725120.V2
Abstract: 2,3-Dihydroxypropanesulfonate (DHPS) is a major sulfur species in the biosphere. One important route for the production of DHPS includes sulfoglycolytic catabolism of sulfoquinovose (SQ) through the Embden-Meyerhof-Parnas (sulfo-EMP) pathway. SQ is a sulfonated carbohydrate present in plant and cyanobacterial sulfolipids (sulfoquinovosyl diacylglyceride and its metabolites) and is biosynthesised globally at a rate of around 10 billion tonnes per annum. The final step in the bacterial sulfo-EMP pathway involves reduction of sulfolactaldehyde (SLA) to DHPS, catalysed by an NADH-dependent SLA reductase. On the basis of conserved sequence motifs, we assign SLA reductase to the β-hydroxyacid dehydrogenase (β-HAD) family, making it the first ex le of a β-HAD enzyme that acts on a sulfonic acid, rather than a carboxylic acid substrate. We report crystal structures of the SLA reductase YihU from E. coli K-12 in its apo and cofactor-bound states, as well as the ternary complex YihU•NADH•DHPS with the cofactor and product bound in the active site. Conformational flexibility observed in these structures, combined with kinetic studies, confirm a sequential mechanism and provide evidence for dynamic domain movements that occur during catalysis. The ternary complex structure reveals a conserved sulfonate pocket in SLA reductase that recognises the sulfonate oxygens through hydrogen bonding to Asn174, Ser178, and the backbone amide of Arg123, along with an ordered water molecule. This triad of residues distinguishes these enzymes from classical β-HADs that act on carboxylate substrates. A comparison of YihU crystal structures with close structural homologues within the β-HAD family highlights key differences in the overall domain organization and identifies a unique peptide sequence that is predictive of SLA reductase activity.
Defining the molecular architecture, metal dependence, and distribution of metal-dependent class II sulfofructose-1-phosphate aldolases
Publisher: American Chemical Society (ACS)
Date: 08-08-2023
DOI: 10.26434/CHEMRXIV-2023-NXMMN
Abstract: Sulfoquinovose (SQ or 6-deoxy-6-sulfoglucose) is a sulfosugar that is the anionic head group of plant and cyanobacterial sulfolipids: sulfoquinovosyl diacylglycerols. SQ is produced within photosynthetic tissues, forms a major terrestrial reservoir of biosulfur, and is an important species within the biogeochemical sulfur cycle. A major pathway for the breakdown of SQ is the sulfoglycolytic Embden-Meyerhof-Parnas (sulfo-EMP) pathway, which involves cleavage of the 6-carbon chain of the intermediate sulfofructose-1-phosphate (SFP) into dihydroxyacetone and sulfolactaldehyde, catalyzed by class I or II SFP aldolases. While the molecular basis of catalysis is well studied for class I SFP aldolases, comparatively little is known about class II SFP aldolases. Here, we report the molecular architecture and biochemical basis of catalysis of two metal-dependent class II SFP aldolases from Hafnia paralvei and Yersinia aldovae. 3D X-ray structures in complex with the substrate SFP and product DHAP reveal a dimer-of-dimers (tetrameric) assembly, and identify the sulfonate binding pocket that defines the substrate specificity of these enzymes, two metal binding sites, and flexible loops that are implicated in catalysis. Both enzymes were metal dependent and exhibited high KM values for SFP, consistent with their role in a unidirectional nutrient acquisition pathway. Bioinformatic analysis identified a range of sulfo-EMP gene clusters containing class I/II SFP aldolases. The class I and II SFP aldolases occur exclusively within Actinobacteria and Firmicutes phyla, respectively, while both classes of enzyme occur within Proteobacteria. This work emphasizes the importance of SQ as a nutrient for erse bacterial phyla and the different chemical strategies they use to harvest carbon from this sulfosugar.
Rapid, iterative assembly of octyl α-1,6-oligomannosides and their 6-deoxy equivalents
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B503919C
Abstract: Mycobacterium tuberculosis is the cause of the deadly human disease tuberculosis. In studies over the last 40 years it has been revealed that this organism possesses a complex cell wall including glycophospholipids such as the phosphatidylinositiol mannosides (PIMs), lipomannan (LM) and lipoarabinomannan (LAM). These glycolipids all contain a common alpha-1,6-linked mannoside core, and the higher PIMs and LAM possess alpha-1,2-linked mannosyl residues. It has been shown that simple alpha-1,6-linked oligomannosides can act as substrates for alpha-1,6-mannosyltransferases in mycobacteria. Here we report a simple iterative synthesis of a series of hydrophobic octyl alpha-1,6-linked oligomannosides from mono- through to tetrasaccharides. We have utilized a single thioglycoside donor and alcohol acceptor. Further, we have developed conditions for the conversion of each of these compounds to the 6-deoxy congeners. Deoxygenation of the 6-position of the terminal mannosyl residue should prevent these compounds acting as substrates for the abundant alpha-1,6-mannosyltransferases in mycobacteria and should permit detection of the elusive alpha-1,2-mannosyltransferase activity responsible for elaboration of LM to mature LAM and the biosynthesis of the higher PIMs.
Molecular basis of sulfolactate synthesis by sulfolactaldehyde dehydrogenase from Rhizobium leguminosarum
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3SC01594G
α-Glucuronosyl and α-Glucosyl Diacylglycerides, Natural Killer T Cell-Activating Lipids from Bacteria and Fungi
Publisher: American Chemical Society (ACS)
Date: 21-10-2019
DOI: 10.26434/CHEMRXIV.9746033.V1
Abstract: Natural killer T cells express T cell receptors (TCRs) that recognize glycolipid antigens in association with the antigen-presenting molecule CD1d. Here, we report the concise chemical synthesis of a range of saturated and unsaturated α-glucosyl and α-glucuronosyl diacylglycerides of bacterial and fungal origins from allyl α-glucoside with Jacobsen kinetic resolution as a key step. We show that these glycolipids could be recognized by a classical type I NKT TCR that uses an invariant Vα14-Jα18 TCR α-chain, but also by an atypical NKT TCR that uses a different TCR α-chain (Vα10-Jα50). In both cases, recognition was sensitive to the lipid fine structure, and included recognition of glycosyl diacylglycerides bearing branched (R- and S-tuberculostearic acid) and unsaturated (oleic and vaccenic) acids. The TCR footprints on CD1d-loaded with a mycobacterial α-glucuronosyl diacylglyceride was assessed using mutant CD1d molecules and, while similar to that for α-GalCer recognition by a type I NKT TCR, were more sensitive to mutations when α-glucuronosyl diacylglyceride was the antigen. In summary, we provide an efficient approach for synthesis of a broad class of bacterial and fungal α-glycosyl diacylglyceride antigens and demonstrate that they can be recognised by TCRs derived from type I and atypical NKT cells.
Protein–carbohydrate interactions: learning lessons from nature
Publisher: Elsevier BV
Date: 09-2001
DOI: 10.1016/S0167-7799(01)01699-7
Abstract: Protein--carbohydrate interactions are at the heart of many important biological processes including signalling, recognition and catalysis. A deeper understanding of these interactions at the molecular level will enable the development of novel, effective and highly selective therapeutics. Glycosyltransferases and glycosidases, carbohydrate-processing enzymes responsible for the synthesis and breakdown of oligosaccharides, have emerged as important targets in the fight against bacterial and fungal pathogenesis, cancer and AIDS. Binding and recognition phenomena are essential processes by which the body exerts control over complex biological functions. In this regard, heparin has retained ongoing interest reflecting its importance as a major pharmaceutical. Recent studies on heparin have shed light onto the mechanisms of cross-reactivity that cause life-threatening side effects and have provided impetus for the development of more selective anti-clotting agents. Important targets for therapeutic intervention are the binding processes mediated through multivalent protein--carbohydrate interactions, such as the interactions of bacterial toxins with cell-surface receptors.
Immune sensing of microbial glycolipids and related conjugates by T cells and the pattern recognition receptors MCL and Mincle
Publisher: Elsevier BV
Date: 02-2016
DOI: 10.1016/J.CARRES.2015.11.009
Abstract: Microbes produce a wide range of small molecule glycoconjugates that constitute unique molecular signatures. These molecules are recognized by a range of detection systems, triggering immune responses to microbial pathogens and commensals. The antigen-presenting molecules of the CD1 class, CD1a-d, capture lipidic molecules and present them to erse and innate-like T cell populations including natural killer T cells and germline-encoded mycolyl reactive T cells. The antigen-presenting molecule MR1 captures vitamin B metabolites and presents them to mucosal associated invariant T cells. In both cases, recognition of the small molecule-antigen presenting molecule complexes occurs through T cell receptors on the surface of T lymphocytes. The pattern recognition receptors macrophage C-type lectin (MCL) and macrophage inducible C-type lectin (Mincle) receptors sense glycolipids and through signalling initiate cellular activation, shaping immune responses to peptide antigens, including the differentiation of naïve T cells into conventional effector T helper cells. In this review, we provide an overview of the erse structures of immunogenic lipidic molecules and vitamin B metabolites and their recognition by select systems of the immune system. Future advances in our understanding of the roles of such molecules in innate and adaptive immune responses will require the coordinated efforts of synthetic and natural products chemists, immunologists and biologists.
Gram scale preparation of clozapine N-oxide (CNO), a synthetic small molecule actuator for muscarinic acetylcholine DREADDs.
Publisher: Elsevier BV
Date: 2018
Spiro‐epoxyglycosides as Activity‐Based Probes for Glycoside Hydrolase Family 99 Endomannosidase/Endomannanase
Publisher: Wiley
Date: 21-06-2018
Distortion of mannoimidazole supports a B2,5 boat transition state for the family GH125 α-1,6-mannosidase from Clostridium perfringens
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9OB01161G
Abstract: Enzyme transition-state mimics can act as powerful inhibitors and allow structural studies that report on the conformation of the transition-state.
Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside
Publisher: American Chemical Society (ACS)
Date: 10-06-2021
DOI: 10.26434/CHEMRXIV.13735084
Abstract: 1,2- i trans /i -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of i /i -nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of i k /i (H sub /sub O sup + /sup )/ i k /i (D sub /sub O) sup + /sup = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of i k /i sub H /sub / i k /i sub D /sub = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect i k /i (H sub /sub O)/ i k /i (D sub /sub O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in sup /sup O-labelled water and H sub /sub O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of i k /i (HO sup – /sup )/ i k /i (DO sup – /sup ) = 0.5 and a strongly negative entropy of activation (D i S /i sup ‡ /sup = –13.6 cal mol sup –1 /sup K sup –1 /sup ). Finally, at high pH, an inverse solvent isotope effect of i k /i (HO sup – /sup )/ i k /i (DO sup – /sup ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step. br
Bacteroides thetaiotaomicron generates diverse α-mannosidase activities through subtle evolution of a distal substrate-binding motif
Publisher: International Union of Crystallography (IUCr)
Date: 24-04-2018
DOI: 10.1107/S2059798318002942
Abstract: A dominant human gut microbe, the well studied symbiont Bacteroides thetaiotaomicron ( Bt ), is a glyco-specialist that harbors a large repertoire of genes devoted to carbohydrate processing. Despite strong similarities among them, many of the encoded enzymes have evolved distinct substrate specificities, and through the clustering of cognate genes within operons termed polysaccharide-utilization loci (PULs) enable the fulfilment of complex biological roles. Structural analyses of two glycoside hydrolase family 92 α-mannosidases, BT3130 and BT3965, together with mechanistically relevant complexes at 1.8–2.5 Å resolution reveal conservation of the global enzyme fold and core catalytic apparatus despite different linkage specificities. Structure comparison shows that Bt differentiates the activity of these enzymes through evolution of a highly variable substrate-binding region immediately adjacent to the active site. These observations unveil a genetic/biochemical mechanism through which polysaccharide-processing bacteria can evolve new and specific biochemical activities from otherwise highly similar gene products.
Copper and Silver Complexes of Tris(triazole)amine and Tris(benzimidazole)amine Ligands: Evidence that Catalysis of an Azide–Alkyne Cycloaddition (“Click”) Reaction by a Silver Tris(triazole)amine Com
Publisher: American Chemical Society (ACS)
Date: 20-06-2014
DOI: 10.1021/IC5008999
Abstract: The synthesis and characterization of a silver complex of the tripodal triazole ligand, tris(benzyltriazolylmethyl)amine (TBTA, L(1)), that is used as promoter to enhance Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. X-ray analysis of the silver(I) complex with L(1) reveals a dinuclear cation, [Ag2(L(1))2](2+), that is essentially isostructural to the copper(I) analogue. While the [Ag2(L(1))2](BF4)2 complex provides catalysis for the azide-alkyne cycloaddition process, evidence is presented that this arises from trace copper contamination. The synthesis of silver(I), copper(II), and copper(I) complexes of a second tripodal ligand, tris(2-benzimidazolymethyl)amine (L(2)), which is used to enhance the rate of CuAAC reactions, is also reported. X-ray crystallography of the Cu(I) complex [Cu(I)3(L(2))2(CH3CN)2](BF4)3 offers structural insight into previous mechanistic speculation about the role of this ligand in the CuAAC reaction.
Vaccine efficacy of an attenuated but persistent Mycobacterium tuberculosis cysH mutant
Publisher: Microbiology Society
Date: 04-2007
Abstract: The emergence of drug-resistant Mycobacterium tuberculosis strains and the widespread occurrence of AIDS demand newer and more efficient control of tuberculosis. The protective efficacy of the current Mycobacterium bovis bacille Calmette–Guérin (BCG) vaccine is highly variable. Therefore, development of an effective new vaccine has gained momentum in recent years. Recently, several M. tuberculosis mutants were tested as potential vaccine candidates in the mouse model of tuberculosis. However, only some of these mutants were able to generate protection equivalent to that of BCG in mice. This study reports the vaccine potential of an attenuated 5′-adenosine phosphosulfate reductase mutant (Δ cysH ) of M. tuberculosis . Immunization of mice with either BCG or Δ cysH followed by infection with the virulent M. tuberculosis Erdman strain demonstrated that Δ cysH can generate protection equivalent to that of the BCG vaccine.
Combined Inhibitor Free‐Energy Landscape and Structural Analysis Reports on the Mannosidase Conformational Coordinate
Publisher: Wiley
Date: 11-12-2013
Copper-free palladium-catalyzed Sonogashira and Hiyama cross-couplings using aryl imidazol-1-ylsulfonates
Publisher: Elsevier BV
Date: 06-2010
Anomeric Anhydro Sugars
Publisher: Springer Berlin Heidelberg
Date: 2008
The galanin-3 receptor antagonist, SNAP 37889, reduces operant responding for ethanol in alcohol-preferring rats
Publisher: Elsevier BV
Date: 2011
DOI: 10.1016/J.REGPEP.2010.08.009
Abstract: The galanin-3 receptor (GALR3) subtype has been identified as having a role in both feeding behaviour and the regulation of emotional states including anxiety. Despite the evidence for an association between galanin and alcohol, the current study is the first to explore the direct role of GALR3 in this context. The present study investigated the potential of the novel selective GALR3 antagonist, SNAP 37889, to reduce anxiety-like behaviour and voluntary ethanol consumption in the iP (alcohol-preferring) rat. This was achieved through a number of behavioural paradigms testing for anxiety, along with the operant self-administration model. Overall, male iP rats treated with SNAP 37889 at a dose of 30 mg/kg (i.p.) did not show altered locomotor activity or changes in anxiety-like behaviour in the elevated plus maze or light-dark paradigms. Treatment with SNAP 37889 (30 mg/kg, i.p.) reduced operant responding for solutions containing ethanol, sucrose and saccharin. Collectively, results from the current study showed that SNAP 37889 (30 mg/kg, i.p.) is effective in reducing operant responding for ethanol, independent of a sedative effect. These findings provide evidence that GALR3 antagonism reduces alcohol consumption and further suggest that GALR3 may be implicated in the rewarding effects of natural and drug reinforcers.
Discovery and Biosynthesis of the Cytotoxic Polyene Terpenomycin in Human Pathogenic Nocardia
Publisher: American Chemical Society (ACS)
Date: 27-07-2023
Structure, Function and Mechanism of N‐Glycan Processing Enzymes: endo‐α‐1,2‐Mannanase and endo‐α‐1,2‐Mannosidase
Publisher: Wiley
Date: 19-10-2022
Abstract: While most glycosidases that act on N‐linked glycans remove a single sugar residue at a time, endo ‐α‐1,2‐mannosidases and endo ‐α‐1,2‐mannanases of glycoside hydrolase family GH99 cut within a chain and remove two or more sugar residues. They are stereochemically retaining enzymes that use an enzymatic mechanism involving an epoxide intermediate. Human endo ‐α‐1,2‐mannosidase (MANEA) trims glucosylated mannose residues the endomannosidase pathway provides a glucosidase‐independent pathway for glycoprotein maturation. Cell‐active MANEA inhibitors alter N‐glycan processing and reduce infectivity of dengue virus, demonstrating that MANEA has potential as a host‐directed antiviral target. Sequence‐related enzymes from gut Bacteroides spp. exhibit endo ‐α‐1,2‐mannosidase activity and are a fruitful test bed for structure‐guided inhibitor development. The genes encoding the Bacteroides spp. enzymes sit within polysaccharide utilization loci and are preferential endo ‐α‐1,2‐mannanases.
Synthesis of Sulfoquinovose and Sulfoquinovosyl Diacylglycerides, and a Fluorogenic Substrate for Sulfoquinovosidases
Publisher: American Chemical Society (ACS)
Date: 02-12-2019
DOI: 10.26434/CHEMRXIV.10566101.V1
Abstract: The sulfolipid sulfoquinovosyl diacylglycerol (SQDG) and its headgroup, the sulfosugar sulfoquinovose (SQ), are estimated to harbour up to half of all organosulfur in the biosphere. SQ is liberated from SQDG and related glycosides by the action of sulfoquinovosidases (SQases). We report a 10-step synthesis of SQDG that we apply to the preparation of saturated and unsaturated lipoforms. We also report an expeditious synthesis of SQ and ( 13 C 6 )SQ, and X-ray crystal structures of sodium and potassium salts of SQ. Finally, we report the synthesis of a fluorogenic SQase substrate, methylumbelliferyl a-D-sulfoquinovoside, and examination of its cleavage kinetics by two recombinant SQases.
The mycobacterial glycoside hydrolase LamH enables capsular arabinomannan release and stimulates growth
Publisher: Cold Spring Harbor Laboratory
Date: 26-10-2023
Identification of d-arabinan-degrading enzymes in mycobacteria
Publisher: Springer Science and Business Media LLC
Date: 19-04-2023
DOI: 10.1038/S41467-023-37839-5
Abstract: Bacterial cell growth and ision require the coordinated action of enzymes that synthesize and degrade cell wall polymers. Here, we identify enzymes that cleave the d -arabinan core of arabinogalactan, an unusual component of the cell wall of Mycobacterium tuberculosis and other mycobacteria. We screened 14 human gut-derived Bacteroidetes for arabinogalactan-degrading activities and identified four families of glycoside hydrolases with activity against the d -arabinan or d -galactan components of arabinogalactan. Using one of these isolates with exo- d -galactofuranosidase activity, we generated enriched d -arabinan and used it to identify a strain of Dysgonomonas gadei as a d -arabinan degrader. This enabled the discovery of endo- and exo-acting enzymes that cleave d -arabinan, including members of the DUF2961 family (GH172) and a family of glycoside hydrolases (DUF4185/GH183) that display endo- d -arabinofuranase activity and are conserved in mycobacteria and other microbes. Mycobacterial genomes encode two conserved endo- d -arabinanases with different preferences for the d -arabinan-containing cell wall components arabinogalactan and lipoarabinomannan, suggesting they are important for cell wall modification and/or degradation. The discovery of these enzymes will support future studies into the structure and function of the mycobacterial cell wall.
Glycoconjugates: Structure and Biosynthesis
Publisher: Wiley
Date: 15-05-2008
DOI: 10.1002/9780470048672.WECB204
Abstract: Carbohydrates are frequently found attached to lipids (e.g., glycoglycerolipids and glycosphingolipids), proteins (glycoproteins and proteoglycans), or in some cases, both (glycosylphosphatidylinositol‐anchored proteins). Three main types of protein modification are found in vertebrates: N ‐linked glycosylation, O‐ linked glycosylation, and the attachment of glycosylphosphatidylinositol anchors also, a fourth rarer type, C‐ mannosylation, is found. In the main types, the biosynthesis of glycoconjugates occurs in two specialized, membranous biosynthetic compartments within the cell: the endoplasmic reticulum and the Golgi apparatus. Degradation of glycoconjugates occurs in another specialized membranous digestive compartment: the lysosome. The two major groups of enzymes that mediate the biosynthesis and degradation of glycoconjugates are glycosyltransferases and glycoside hydrolases. This article will review the classification and mechanisms of glycosyltransferases and glycoside hydrolases and give an overview of their roles in the biosynthesis and degradation of vertebrate glycoconjugates: glycolipids, glycoproteins, proteoglycans, and glycosylphosphatidylinositol anchors.
An Epoxide Intermediate in Glycosidase Catalysis
Publisher: American Chemical Society (ACS)
Date: 16-04-2020
Active-site Peptide “Fingerprinting” of Glycosidases in Complex Mixtures by Mass Spectrometry
Publisher: Elsevier BV
Date: 10-2005
α-glucosidase inhibitors as host-directed antiviral agents with potential for the treatment of COVID-19
Publisher: Portland Press Ltd.
Date: 08-06-2020
DOI: 10.1042/BST20200505
Abstract: The ongoing COVID-19 pandemic, caused by SARS-CoV-2, has pushed the health systems of many countries to breaking point and precipitated social distancing measures that have crippled economic activities across the globe. A return to normality is unlikely until effective therapeutics and a vaccine are available. The immediacy of this problem suggests that drug strategies should focus on repurposing approved drugs or late-stage clinical candidates, as these have the shortest path to use in the clinic. Here, we review and discuss the role of host cell N-glycosylation pathways to virus replication and the drugs available to disrupt these pathways. In particular, we make a case for evaluation of the well-tolerated drugs miglitol, celgosivir and especially miglustat for the treatment of COVID-19.
Atomic resolution analyses of the binding of xylobiose-derived deoxynojirimycin and isofagomine to xylanase Xyn10AElectronic supplementary information (ESI) available: kinetics and structural methods.
Publisher: Royal Society of Chemistry (RSC)
Date: 2004
DOI: 10.1039/B405152A
Abstract: The atomic resolution structures of xylobiose-derived isofagomine and xylobiose-derived deoxynojirimycin in complex with the xylanase Xyn10A from Streptomyces lividans reveal undistorted (4)C(1) chair conformed sugars and, in the case of the deoxynojirimycin analogue, suggest unusual pK(a) changes of the enzyme's catalytic machinery upon binding.
Exploration of Strategies for Mechanism‐Based Inhibitor Design for Family GH99 endo‐α‐1,2‐Mannanases
Publisher: Wiley
Date: 30-04-2018
Neighboring Group Participation in Glycosylation Reactions by 2,6-Disubstituted 2-O-Benzoyl groups: A Mechanistic Investigation
Publisher: Informa UK Limited
Date: 07-2010
Structure–reactivity correlations of the abnormal Beckmann reaction of dihydrolevoglucosenone oxime
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7OB02499A
Abstract: Structural, spectroscopic and computational studies of a series of oximes reveals ground state structural manifestations relevant to the reaction coordinate for the Beckmann rearrangement (normal Beckmann) and Beckmann fragmentation (abnormal Beckmann).
Dynamic Structural Changes Accompany the Production of Dihydroxypropanesulfonate by Sulfolactaldehyde Reductase
Publisher: American Chemical Society (ACS)
Date: 30-01-2020
Effects of 3′,4′-dihydroxyflavonol on vascular contractions of rat aortic rings
Publisher: Wiley
Date: 27-07-2010
DOI: 10.1111/J.1440-1681.2010.05384.X
Abstract: 1. 3',4'-Dihydroxyflavonol (DiOHF) is an effective vasodilator with anti-oxidant activity. The aim of the present study was to elucidate the effects of DiOHF on vascular contractions. 2. Contractile and relaxation responses were determined in rat endothelium-denuded aortic rings mounted in organ baths. In addition, the phosphorylation of myosin light chain (MLC(20)), myosin phosphatase targeting subunit 1 (MYPT1) and protein kinase C (PKC)-potentiated inhibitory protein for heterotrimeric myosin light chain phosphatase of 17 kDa (CPI-17) was determined using western blot analysis. Levels of GTP RhoA, as a marker of RhoA activation, were also measured. 3. Cumulative addition of increasing concentrations of NaF (3.0-12.0 mmol/L) or U46619 (1.0-1000 nmol/L) concentration-dependently increased vascular tension. These responses were inhibited by pretreatment of aortic rings with DiOHF (10, 30 or 100 micromol/L), which dose-dependently decreased vascular contractions induced by 8.0 mmol/L NaF, 30 nmol/L U46619, 0.1 micromol/L phenylephrine and 50 mmol/L KCl. 4. The K(+) channel blockers 4-aminopyridine (3 mmol/L), charybdotoxin (10 nmol/L), apamin (500 nmol/L) and glibenclamide (10 micromol/L) had no effect on vascular relaxation induced by DiOHF (1-30 micromol/L). 5. At 30 micromol/L, DiOHF decreased the activation of RhoA and subsequent phosphorylation of MYPT1, CPI-17 and MLC(20) to almost basal levels. 6. In conclusion, DiOHF decreases vascular contraction at least partly by inhibition of the RhoA/Rho-kinase pathway in rat endothelium-denuded aorta. These results suggest that DiOHF may have therapeutic potential in the treatment of cardiovascular diseases.
Mining the human gut microbiome identifies mycobacterial d-arabinan degrading enzymes
Publisher: Cold Spring Harbor Laboratory
Date: 23-07-2022
DOI: 10.1101/2022.07.22.500997
Abstract: Division and degradation of bacterial cell walls requires coordinated action of a myriad of enzymes. This particularly applies to the elaborate cell walls of acid-fast organisms such as Mycobacterium tuberculosis , which consist of a multi-layered cell wall that contains an unusual glycan called arabinogalactan. Enzymes that cleave the d -arabinan core of this structure have not previously been identified in any organism. We have interrogated the erse carbohydrate degrading enzymes expressed by the human gut microbiota and uncovered four families of glycoside hydrolases with the capability to degrade the d -arabinan or d -galactan components of arabinogalactan. Using novel exo- d -galactofuranosidases from gut bacteria we generated enriched d -arabinan and used it to identify D. gadei as a D-arabinan degrader. This enabled the discovery of endo- and exo-acting enzymes that cleave D-arabinan. We have identified new members of the DUF2961 family (GH172), and a novel family of glycoside hydrolases (DUF4185) that display endo- d -arabinofuranase activity. The DUF4185 enzymes are conserved in mycobacteria and found in many microbes, suggesting that the ability to degrade mycobacterial glycans plays an important role in the biology of erse organisms. All mycobacteria encode two conserved endo- d -arabinanases that display different preferences for the d -arabinan-containing cell wall components arabinogalactan and lipoarabinomannan, suggesting they are important for cell wall modification and/or degradation. The discovery of these enzymes will support future studies into the structure and function of the mycobacterial cell wall.
Conjugation of Transferrin to Azide‐Modified CdSe/ZnS Core–Shell Quantum Dots using Cyclooctyne Click Chemistry
Publisher: Wiley
Date: 20-09-2012
Abstract: Twinkle twinkle quantum dot: Conjugation of biomolecules to azide-modified quantum dots (QDs) through a bifunctional linker, using strain-promoted azide-alkyne cycloaddition with the QD and a squaramide linkage to the biomolecule (see scheme). Transferrin-conjugated QDs were internalized by transferrin-receptor expressing HeLa cells.
An improved method to prepare an injectable microemulsion of the galanin-receptor 3 selective antagonist, SNAP 37889, using Kolliphor® HS 15
Publisher: Elsevier BV
Date: 2014
Gas-Phase Structural and Optical Properties of Homo- and Heterobimetallic Rhombic Dodecahedral Nanoclusters [Ag14–nCun(C≡CtBu)12X]+ (X
Publisher: American Chemical Society (ACS)
Date: 05-05-2017
1,6-epithio- and 1,6-episeleno-β-d-glucopyranose: Useful adjuncts in the synthesis of 6-deoxy-β-d-glucopyranosides
Publisher: Elsevier BV
Date: 04-1997
A surface endogalactanase in Bacteroides thetaiotaomicron confers keystone status for arabinogalactan degradation
Publisher: Springer Science and Business Media LLC
Date: 22-10-2018
Conformational Analysis of the Mannosidase Inhibitor Kifunensine: A Quantum Mechanical and Structural Approach
Publisher: Wiley
Date: 26-06-2017
Abstract: The varied yet family-specific conformational pathways used by in idual glycoside hydrolases (GHs) offer a tantalising prospect for the design of tightly binding and specific enzyme inhibitors. A cardinal ex le of a GH-family-specific inhibitor, and one that finds widespread practical use, is the natural product kifunensine, which is a low-nanomolar inhibitor that is selective for GH family 47 inverting α-mannosidases. Here we show, through quantum-mechanical approaches, that kifunensine is restrained to a "ring-flipped"
Design of Potent Mincle Signalling Agonists Based on an Alkyl b- Glucoside Template
Publisher: American Chemical Society (ACS)
Date: 17-01-2020
DOI: 10.26434/CHEMRXIV.10567097.V1
Abstract: The innate immune receptor Mincle senses lipid-based molecules derived from pathogens, commensals and altered self. Based on emerging structure-activity relationships we design simple alkyl 6- O -acyl-b-D-glucosides that are effective agonists of Mincle and signal with potency on par with the prototypical ligand trehalose dimycolate.
A broad-spectrum α-glucosidase of glycoside hydrolase family 13 fromMarinovumsp., a member of theRoseobacterclade
Publisher: Cold Spring Harbor Laboratory
Date: 04-2023
DOI: 10.1101/2023.03.31.535182
Abstract: Glycoside hydrolases (GHs) are a erse group of enzymes that catalyze the hydrolysis of glycosidic bonds. The Carbohydrate-Active enZymes (CAZy) classification organizes GHs into families based on sequence data and function, with fewer than 1% of the predicted proteins characterized biochemically. Consideration of genomic context can provide clues to infer possible enzyme activities for proteins of unknown function. We used the MultiGeneBLAST tool to discover a gene cluster in Marinovum sp., a member of the marine Roseobacter clade, that encodes homologues of enzymes belonging to the sulfoquinovose monooxygenase pathway for sulfosugar catabolism. This cluster lacks a gene encoding a classical family GH31 sulfoquinovosidase candidate, but which instead includes an uncharacterized family GH13 protein ( Ms GH13) that we hypothesized could be a non-classical sulfoquinovosidase. Surprisingly, recombinant Ms GH13 lacks sulfoquinovosidase activity and is a broad spectrum α-glucosidase that is active on a erse array of α-linked disaccharides, including: maltose, sucrose, nigerose, trehalose, isomaltose, and kojibiose. Using AlphaFold, a 3D model for the Ms GH13 enzyme was constructed that predicted its active site shared close similarity with an α-glucosidase from Halomonas sp. H11 of the same GH13 subfamily that shows narrower substrate specificity.
Oxidative desulfurization pathway for complete catabolism of sulfoquinovose by bacteria
Publisher: Cambridge University Press (CUP)
Date: 09-2021
DOI: 10.33774/CHEMRXIV-2021-08J01-V4
Abstract: Catabolism of sulfoquinovose (SQ, 6-deoxy-6-sulfoglucose), the ubiquitous sulfosugar produced by photosynthetic organisms, is an important component of the biogeochemical carbon and sulfur cycles. Here, we describe a new pathway for SQ degradation that involves oxidative desulfurization to release sulfite and enable utilization of the entire carbon skeleton of the sugar to support the growth of the plant pathogen Agrobacterium tumefaciens. SQ or its glycoside sulfoquinovosyl glycerol (SQGro) are imported into the cell by an ABC transporter system with an associated SQ binding protein. A sulfoquinovosidase hydrolyses the SQ glycoside and the liberated SQ is acted on by a flavin mononucleotide-dependent sulfoquinovose monooxygenase, in concert with an NADH-dependent flavin reductase, to release sulfite and 6-oxo-glucose. An NADPH-dependent oxidoreductase reduces the 6-oxo-glucose to glucose, enabling entry into primary metabolic pathways. Structural and biochemical studies provide detailed insights into the recognition of key metabolites by proteins in this pathway. Bioinformatic analyses reveal that the sulfoquinovose monooxygenase (smo) pathway is distributed across Alpha- and Betaproteobacteria and is especially prevalent within the Rhizobiales order. This strategy for SQ catabolism is distinct from previously described pathways as it enables the complete utilization of all carbons within SQ by a single organism with concomitant production of inorganic sulfite.
The Molecular Basis of Sulfosugar Selectivity in Sulfoglycolysis
Publisher: American Chemical Society (ACS)
Date: 09-02-2021
DOI: 10.26434/CHEMRXIV.12974237
Abstract: The sulfosugar sulfoquinovose (SQ) is produced by essentially all photosynthetic organisms on earth and is metabolized by bacteria through the process of sulfoglycolysis. The sulfoglycolytic Embden-Meyerhof-Parnas pathway metabolises SQ to produce dihydroxyacetone phosphate and sulfolactaldehyde and is analogous to the classical Embden-Meyerhof-Parnas glycolysis pathway for the metabolism of glucose-6-phosphate, though the former only provides one C3 fragment to central metabolism, with excretion of the other C3 fragment as dihydroxypropanesulfonate. Here, we report a comprehensive structural and biochemical analysis of the three core steps of sulfoglycolysis catalyzed by SQ isomerase, sulfofructose (SF) kinase and sulfofructose-1-phosphate (SFP) aldolase. Our data shows that despite the superficial similarity of this pathway to glycolysis, the sulfoglycolytic enzymes are specific for SQ metabolites and are not catalytically active on related metabolites from glycolytic pathways. This observation is rationalized by 3D structures of each enzyme, which reveal the presence of conserved sulfonate-binding pockets. We show that SQ isomerase acts preferentially on the β-anomer of SQ and reversibly produces both SF and sulforhamnose (SR), a previously unknown sugar that acts as a transcriptional regulator for the transcriptional repressor CsqR that regulates SQ-utilization. We also demonstrate that SF kinase is a key regulatory enzyme for the pathway that experiences complex modulation by the metabolites AMP, ADP, ATP, F6P, FBP, PEP, and citrate, and we show that SFP aldolase reversibly synthesizes SFP. This body of work provides fresh insights into the mechanism, specificity and regulation of sulfoglycolysis and has important implications for understanding how this biochemistry interfaces with central metabolism in prokaryotes to process this major repository of biogeochemical sulfur.
The Reaction Coordinate of a Bacterial GH47 α‐Mannosidase: A Combined Quantum Mechanical and Structural Approach
Publisher: Wiley
Date: 26-09-2012
Abstract: Mannosides in the southern hemisphere: Conformational analysis of enzymatic mannoside hydrolysis informs strategies for enzyme inhibition and inspires solutions to mannoside synthesis. Atomic resolution structures along the reaction coordinate of an inverting α-mannosidase show how the enzyme distorts the substrate and transition state. QM/MM calculations reveal how the free energy landscape of isolated α-D-mannose is molded on enzyme to only allow one conformationally accessible reaction coordinate.
An atypical interaction explains the high-affinity of a non-hydrolyzable S-linked 1,6-α-mannanase inhibitor
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CC04977C
Abstract: The non-hydrolyzable S-linked azasugar 1,6-α-mannobiosylthioisofagomine effects potent inhibition of Bacillus circulans family 76 endo -1,6-α-mannanase through an atypical interaction involving the acid/base residue of the enzyme.
Synthesis and Preliminary Pharmacological Evaluation of Aryl Dithiolethiones with Cyclooxygenase-2-Selective Inhibitory Activity and Hydrogen Sulfide-Releasing Properties
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/CH09517
Abstract: A series of 5-aryl-1,2-dithiolethiones and 5-aryl-1,2-dithiole-3-ones were investigated as hydrogen sulfide-releasing anti-inflammatory drugs. Generally, phenolic acetophenones were best protected by methoxymethyl groups and the dithiolethione group installed by treatment with carbon disulfide, hexamethyldisilathiane, and hexachloroethane. However, ether-protected acetophenones could be elaborated to β-keto esters and converted to dithiolethiones by treatment with phosphorus pentasulfide and elemental sulfur. Dethionation of dithiolethiones to 1,2-dithiole-3-ones was accomplished by mercury(ii)-promoted hydrolysis. A preliminary investigation of the dithiolethiones and dithiole-3-ones as inhibitors of cyclooxygenases COX-1 and COX-2 is discussed. Dithiolethiones bearing a 5-(2,6-di-tert-butyl-4-hydroxyphenyl) or 5-(2,6-di-tert-butyl-4-methoxyphenyl) substituent were the most effective inhibitors of COX-2 and displayed excellent selectivity against COX-1, comparable with rofecoxib, a representative coxib. It is shown that uncatalyzed hydrolysis of the thiocarbonyl group to release hydrogen sulfide leads to the corresponding carbonyl compound, and these carbonyl compounds are moderate COX-2 selective inhibitors.
Identification of levoglucosan degradation pathways in bacteria and sequence similarity network analysis
Publisher: Springer Science and Business Media LLC
Date: 31-03-2023
DOI: 10.1007/S00203-023-03506-Y
Abstract: Levoglucosan is produced in the pyrolysis of cellulose and starch, including from bushfires or the burning of biofuels, and is deposited from the atmosphere across the surface of the earth. We describe two levoglucosan degrading Paenarthrobacter spp. ( Paenarthrobacter nitrojuajacolis LG01 and Paenarthrobacter histidinolovorans LG02) that were isolated from soil by metabolic enrichment using levoglucosan as the sole carbon source. Genome sequencing and proteomics analysis revealed the expression of a series of genes encoding known levoglucosan degrading enzymes, levoglucosan dehydrogenase (LGDH, LgdA), 3-keto-levoglucosan β -eliminase (LgdB1) and glucose 3-dehydrogenase (LgdC), along with an ABC transporter cassette and an associated solute binding protein. However, no homologues of 3-ketoglucose dehydratase (LgdB2) were evident, while the expressed genes contained a range of putative sugar phosphate isomerases/xylose isomerases with weak similarity to LgdB2. Sequence similarity network analysis of genome neighbours of LgdA revealed that homologues of LgdB1 and LgdC are generally conserved in a range of bacteria in the phyla Firmicutes, Actinobacteria and Proteobacteria. One group of sugar phosphate isomerase/xylose isomerase homologues (named LgdB3) was identified with limited distribution that is mutually exclusive with LgdB2, and we propose that they may fulfil a similar function. LgdB1, LgdB2 and LgdB3 adopt similar predicted 3D folds, suggesting overlapping function in processing intermediates in LG metabolism. Our findings highlight ersity within the LGDH pathway, through which bacteria utilize levoglucosan as a nutrient source.
Evaluation and optimization of antifibrotic activity of cinnamoyl anthranilates
Publisher: Elsevier BV
Date: 12-2009
DOI: 10.1016/J.BMCL.2009.09.120
Abstract: Tranilast is an anti-inflammatory drug in use for asthma and atopic dermatitis. In studies over the last decade it has been revealed that tranilast can reduce fibrosis occurring in the kidney during diabetes, thereby delaying and/or preventing kidney dysfunction. We report a structure-activity study aimed at optimizing the antifibrotic activity of tranilast. A series of cinnamoyl anthranilates were prepared and assessed for their ability to prevent TGF-beta-stimulated production of collagen in cultured renal mesangial cells. We reveal derivatives with improved potency and reduced cellular toxicity relative to tranilast. 3-Methoxy-4-propargyloxycinnamoyl anthranilate reduces albuminuria in a rat model of progressive diabetes, and thus has potential as an innovative treatment for diabetic nephropathy.
Dissecting conformational contributions to glycosidase catalysis and inhibition
Publisher: Elsevier BV
Date: 10-2014
3′,4′-Dihydroxyflavonol reduces vascular contraction through Ca 2+ desensitization in permeabilized rat mesenteric artery
Publisher: Springer Science and Business Media LLC
Date: 14-10-2012
DOI: 10.1007/S00210-011-0697-8
Abstract: 3',4'-Dihydroxyflavonol (DiOHF) exerts endothelium-independent relaxation in rat aortic rings. In this study, we hypothesized that DiOHF reduces vascular contraction through Ca²⁺ desensitization in permeabilized third-order branches of rat mesenteric arteries. The third-order branches of rat mesenteric arteries were permeabilized with β-escin and subjected to tension measurement. Cumulative addition of phenylephrine (0.3-30 μM) produced concentration-dependent vascular contraction of endothelium-intact and endothelium-denuded arterial rings, which were inhibited by pretreatment with DiOHF (10, 30, or 100 μM). In addition, DiOHF dose-dependently decreased vascular contractions induced by 3.0 μM phenylephrine. β-Escin-permeabilized third-order branches of mesenteric arteries were contracted with Ca²⁺, NaF, or guanosine-5'-(γ-thio)triphosphate (GTPγS) 30 min after pretreatment with DiOHF or vehicle. Pretreatment with DiOHF for 30 min inhibited vascular contraction induced by cumulative additions of Ca²⁺ (pCa 9.0-6.0) or NaF (4.0-16.0 mM) in permeabilized arterial rings. Cumulative addition of DiOHF also reduced vascular contraction induced by Ca²⁺-controlled solution of pCa 6.0, 16.0 mM NaF, or 100 μM GTPγS in permeabilized arterial rings. DiOHF inhibited the increase in vascular tension provoked by calyculin A, even though it did not affect vascular tension already produced by calyculin A. DiOHF accelerated the relaxation induced by rapidly lowering Ca²⁺. DiOHF reduced vascular contraction through Ca²⁺ desensitization in permeabilized third-order branches of rat mesenteric arteries. These results suggest that DiOHF may have a therapeutic potential in the treatment of cardiovascular diseases.
Remodeling of Carbon Metabolism during Sulfoglycolysis in Escherichia coli
Publisher: American Society for Microbiology
Date: 28-02-2023
DOI: 10.1128/AEM.02016-22
Abstract: The sulfosugar sulfoquinovose is estimated to be produced on a scale of 10 billion metric tons per annum, making it a major organosulfur species in the biosulfur cycle. The microbial degradation of sulfoquinovose through sulfoglycolysis allows the utilization of its carbon content and contributes to the biomineralization of its sulfur.
Characterization of Mycobacterium tuberculosis Mycolic Acids by Multiple-Stage Linear Ion-Trap Mass Spectrometry
Publisher: American Chemical Society (ACS)
Date: 29-11-2021
‘Click’ cycloaddition catalysts: copper(i) and copper(ii) tris(triazolylmethyl)amine complexes
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B719724A
Abstract: The CuI complex of the 'click' ligand tris(benzyltriazolylmethyl)amine is an unusual dinuclear dication with one triazole unit bridging two metal centers, and is an effective catalyst for the 'click' cycloaddition reaction.
Structural and Kinetic Dissection of the endo -α-1,2-Mannanase Activity of Bacterial GH99 Glycoside Hydrolases from Bacteroides spp.
Publisher: Wiley
Date: 08-12-2014
Abstract: Glycoside hydrolase family 99 (GH99) was created to categorize sequence-related glycosidases possessing endo-α-mannosidase activity: the cleavage of mannosidic linkages within eukaryotic N-glycan precursors (Glc1-3 Man9 GlcNAc2 ), releasing mono-, di- and triglucosylated-mannose (Glc1-3 -1,3-Man). GH99 family members have recently been implicated in the ability of Bacteroides spp., present within the gut microbiota, to metabolize fungal cell wall α-mannans, releasing α-1,3-mannobiose by hydrolysing αMan-1,3-αMan→1,2-αMan-1,2-αMan sequences within branches off the main α-1,6-mannan backbone. We report the development of a series of substrates and inhibitors, which we use to kinetically and structurally characterise this novel endo-α-1,2-mannanase activity of bacterial GH99 enzymes from Bacteroides thetaiotaomicron and xylanisolvens. These data reveal an approximate 5 kJ mol(-1) preference for mannose-configured substrates in the -2 subsite (relative to glucose), which inspired the development of a new inhibitor, α-mannopyranosyl-1,3-isofagomine (ManIFG), the most potent (bacterial) GH99 inhibitor reported to date. X-ray structures of ManIFG or a substrate in complex with wild-type or inactive mutants, respectively, of B. xylanisolvens GH99 reveal the structural basis for binding to D-mannose- rather than D-glucose-configured substrates.
Helicobacter pylori metabolites exacerbate gastritis through C-type lectin receptors
Publisher: Rockefeller University Press
Date: 29-09-2020
DOI: 10.1084/JEM.20200815
Abstract: Helicobacter pylori causes gastritis, which has been attributed to the development of H. pylori–specific T cells during infection. However, the mechanism underlying innate immune detection leading to the priming of T cells is not fully understood, as H. pylori evades TLR detection. Here, we report that H. pylori metabolites modified from host cholesterol exacerbate gastritis through the interaction with C-type lectin receptors. Cholesteryl acyl α-glucoside (αCAG) and cholesteryl phosphatidyl α-glucoside (αCPG) were identified as noncanonical ligands for Mincle (Clec4e) and DCAR (Clec4b1). During chronic infection, H. pylori–specific T cell responses and gastritis were ameliorated in Mincle-deficient mice, although bacterial burdens remained unchanged. Furthermore, a mutant H. pylori strain lacking αCAG and αCPG exhibited an impaired ability to cause gastritis. Thus H. pylori–specific modification of host cholesterol plays a pathophysiological role that exacerbates gastric inflammation by triggering C-type lectin receptors.
Correction to “Synthetic β-1,2-Mannosyloxymannitol Glycolipid from the Fungus Malassezia pachydermatis Signals through Human Mincle”
Publisher: American Chemical Society (ACS)
Date: 27-06-2019
A Synthesis of (Z)-Octadec-9-enedioic Acid
Publisher: CSIRO Publishing
Date: 1995
DOI: 10.1071/CH9951893
Abstract: The monomethyl ester of azelaic acid was transformed into two fragments, namely [8-( methoxy -carbonyl) octyl ] triphenylphosphonium bromide and methyl 9-oxononanoate. A Wittig reaction between these two fragments produced dimethyl (Z)-octadec-9-enedioate and subsequent hydrolysis gave the title diacid. Interestingly, the same diacid was available directly from oleic acid in a published procedure which utilized a mutant strain of Candida tropicalis.
Discovery of water-soluble antioxidant flavonols without vasorelaxant activity
Publisher: Wiley
Date: 10-10-2008
Abstract: 3',4'-Dihydroxyflavonol (DiOHF) is a cardioprotective flavonol that can decrease ischaemia/reperfusion injury in the heart. DiOHF exhibits antioxidant and vasorelaxant properties that are thought to underlie its cardioprotective activity. A major limitation to its use for the treatment or prevention of cardiovascular disease is its poor water solubility, preventing intravenous administration at the required dosage. In this study, three novel flavonols were synthesised that bear an ionisable succinamic acid substituent at the 6-position of the A ring with zero, one, or two hydroxy groups on the B ring. The ionised compounds possess improved aqueous solubility, dissolving at concentrations up to 10(-1) m, whereas DiOHF is insoluble in water (<10(-7) m). Pharmacological analysis revealed that the DiOHF-6-succinamic acid derivative was the best antioxidant, possessing activity similar to DiOHF, whereas vasorelaxant activity was attenuated. This compound was able to effectively scavenge superoxide from the autoxidation of pyrogallol, preventing oxidant-induced endothelial dysfunction. DiOHF-6-succinamic acid represents the first antioxidant flavonol that lacks vasorelaxant activity and in the future will enable studies to cast light on the specific biological activity required for cardioprotection.
Cholesteryl 6-O-acyl-α-glucosides from diverse Helicobacter spp. signal through the C-type lectin receptor Mincle
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0OB01776K
Abstract: Stereoselective α-glucosylation of cholesterol enabled synthesis of cholesteryl 6- O -acyl-glucosides from erse Helicobacter spp. and demonstration that they signal through the innate immune receptor Mincle.
Eucalyptus subgenus Eucalyptus (Myrtaceae) trees are abundant sources of medicinal pinocembrin and related methylated flavanones
Publisher: Elsevier BV
Date: 05-2019
Total syntheses of cis-cyclopropane fatty acids: dihydromalvalic acid, dihydrosterculic acid, lactobacillic acid, and 9,10-methylenehexadecanoic acid
Publisher: Royal Society of Chemistry (RSC)
Date: 06-10-2014
DOI: 10.1039/C4OB01863J
Abstract: cis-Cyclopropane fatty acids (cis-CFAs) are widespread constituents of the seed oils of subtropical plants, membrane components of bacteria and protozoa, and the fats and phospholipids of animals. We describe a systematic approach to the synthesis of enantiomeric pairs of four cis-CFAs: cis-9,10-methylenehexadecanoic acid, lactobacillic acid, dihydromalvalic acid, and dihydrosterculic acid. The approach commences with Rh2(OAc)4-catalyzed cyclopropenation of 1-octyne and 1-decyne, and hinges on the preparative scale chromatographic resolution of racemic 2-alkylcycloprop-2-ene-1-carboxylic acids using a homochiral Evan's auxiliary. Saturation of the in idual diastereomeric N-cycloprop-2-ene-1-carbonylacyloxazolidines, followed by elaboration to alkylcyclopropylmethylsulfones, allowed Julia-Kocienski olefination with various ω-aldehyde-esters. Finally, saponification and diimide reduction afforded the in idual cis-CFA enantiomers.
Total Synthesis of Mycobacterium tuberculosis Dideoxymycobactin-838 and Stereoisomers: Diverse CD1a-Restricted T Cells Display a Common Hierarchy of Lipopeptide Recognition
Publisher: Wiley
Date: 18-01-2017
Water soluble flavonol prodrugs that protect against ischaemia-reperfusion injury in rat hindlimb and sheep heart
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0MD00240B
Experimental and theoretical insights into the mechanisms of sulfate and sulfamate ester hydrolysis and the end products of type i sulfatase inactivation by aryl sulfamates
Publisher: American Chemical Society (ACS)
Date: 20-02-2014
DOI: 10.1021/JO4026513
Abstract: Type I sulfatases catalyze the hydrolysis of sulfate esters through S-O bond cleavage and possess a catalytically essential formylglycine (FGly) active-site residue that is post-translationally derived from either cysteine or serine. Type I sulfatases are inactivated by aryl sulfamates in a time-dependent, irreversible, and active-site directed manner consistent with covalent modification of the active site. We report a theoretical (SCS-MP2//B3LYP) and experimental study of the uncatalyzed and enzyme-catalyzed hydrolysis of aryl sulfates and sulfamates. In solution, aryl sulfate monoanions undergo hydrolysis by an S(N)2 mechanism whereas aryl sulfamate monoanions follow an S(N)1 pathway with SO2NH as an intermediate theory traces this difference to the markedly greater stability of SO2NH versus SO3. For Pseudomonas aeruginosa arylsulfatase-catalyzed aryl sulfate hydrolysis, Brønsted analysis (log(V(max)/K(M)) versus leaving group pK(a) value) reveals β(LG) = -0.86 ± 0.23, consistent with an S(N)2 at sulfur reaction but substantially smaller than that reported for uncatalyzed hydrolysis (β(LG) = -1.81). Common to all proposed mechanisms of sulfatase catalysis is a sulfated FGly intermediate. Theory indicates a ≥26 kcal/mol preference for the intermediate to release HSO4(-) by an E2 mechanism, rather than alkaline phosphatase-like S(N)2 substitution by water. An evaluation of the stabilities of various proposed end-products of sulfamate-induced sulfatase inactivation highlights that an imine N-sulfate derived from FGly is the most likely irreversible adduct.
Oxidative desulfurization pathway for complete catabolism of sulfoquinovose by bacteria
Publisher: American Chemical Society (ACS)
Date: 23-06-2021
DOI: 10.26434/CHEMRXIV-2021-08J01
Abstract: Breakdown of the sulfosugar sulfoquinovose (SQ, 6-deoxy-6-sulfoglucose), produced by photosynthetic organisms, is an important component of the biogeochemical carbon and sulfur cycles. Here, we reveal a new pathway for SQ degradation involving oxidative desulfurization to release sulfite and complete breakdown of the carbon skeleton of this sugar to support the growth of the plant pathogen Agrobacterium tumefaciens. SQ or its glycoside sulfoquinovosyl glycerol are imported by an ABC transporter system with associated SQ binding protein. A sulfoquinovosidase cleaves the SQ glycoside and a flavin mononucleotide-dependent sulfoquinovose monooxygenase acts in concert with an NADH-dependent flavin reductase to release sulfite and form 6-oxo-glucose. A short-chain dehydrogenase/reductase oxidoreductase reduces 6-oxo-glucose to glucose, allowing it to enter primary metabolism. Structural and biochemical studies provide detailed insights into the binding and recognition of key species along the reaction coordinate. This sulfoquinovose monooxygenase pathway is distributed across alphaproteobacteria and especially within the rhizobiales. This metabolic strategy...
Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside
Publisher: American Chemical Society (ACS)
Date: 12-04-2021
DOI: 10.26434/CHEMRXIV.13735084.V7
Abstract: 1,2- trans -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k (H 3 O + )/ k (D 3 O) + = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside
Publisher: American Chemical Society (ACS)
Date: 30-03-2021
DOI: 10.26434/CHEMRXIV.13735084.V6
Abstract: 1,2- trans -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k (H 3 O + )/ k (D 3 O + = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
Unimolecular, bimolecular and intramolecular hydrolysis mechanisms of 4-nitrophenyl β-D-glucopyranoside
Publisher: American Chemical Society (ACS)
Date: 10-06-2021
DOI: 10.26434/CHEMRXIV.13735084.V8
Abstract: 1,2- trans -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k (H 3 O + )/ k (D 3 O) + = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside
Publisher: American Chemical Society (ACS)
Date: 16-02-2021
DOI: 10.26434/CHEMRXIV.13735084.V3
Abstract: 1,2- trans -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect ( k (H 3 O + )/ k (D 3 O + ) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside
Publisher: American Chemical Society (ACS)
Date: 15-02-2021
DOI: 10.26434/CHEMRXIV.13735084.V2
Abstract: 1,2- trans -Glycosides hydrolyze through a range of mechanisms under conditions of different pH, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect ( k (H 3 O + )/ k (D 3 O + ) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibited general catalysis with a single proton in flight with a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, which is consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, and to a minor degree, nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular dissociative mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (delta S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
pH-Rate Profile for Hydrolysis of 4-Nitrophenyl β-D-Glucopyranoside: Unimolecular, Bimolecular and Intramolecular Cleavage Mechanisms
Publisher: American Chemical Society (ACS)
Date: 10-03-2021
DOI: 10.26434/CHEMRXIV.13735084.V5
Abstract: 1,2- trans -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k (H 3 O + )/ k (D 3 O + = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
pH-Rate Profile for Hydrolysis of 4-Nitrophenyl β-D-Glucopyranoside: Unimolecular, Bimolecular and Intramolecular Cleavage Mechanisms
Publisher: American Chemical Society (ACS)
Date: 09-03-2021
DOI: 10.26434/CHEMRXIV.13735084.V4
Abstract: 1,2- trans -Glycosides hydrolyze through different mechanisms at different pH values, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect of k (H 3 O + )/ k (D 3 O + = 0.65 in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region exhibit general catalysis with a single proton in flight, a normal solvent isotope effect of k H / k D = 1.5, and when extrapolated to zero buffer concentration show a small solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1, consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, with a minor contribution of nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular concerted mechanism is implicated through an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO – )/ k (DO – ) = 0.6 indicates that the formation of 1,2-anhydrosugar is the rate determining step.
Non-volatile components of the essential oil secretory cavities of Eucalyptus leaves: Discovery of two glucose monoterpene esters, cuniloside B and froggattiside A
Publisher: Elsevier BV
Date: 06-2009
DOI: 10.1016/J.PHYTOCHEM.2009.06.004
Abstract: The essential oils extracted from the embedded foliar secretory cavities of many Eucalyptus species are of economic value as pharmaceuticals and fragrance additives. Recent studies have indicated that Eucalyptus secretory cavities may not be exclusively involved in the biosynthesis and storage of essential oils. Therefore, we selected three species upon which to perform an examination of the contents of foliar secretory cavities: Eucalyptus froggattii, E. polybractea and E. globulus. This paper describes the isolation and structural characterization of two non-volatile glucose monoterpene esters, which we have named cuniloside B and froggattiside A, from within the secretory cavities of these species, and shows the presence of these compounds in solvent extracts of the leaves from two other species of Eucalyptus. Both compounds were found in high proportions relative to the essential oils extracted from the leaves. We propose that many other carbohydrate monoterpene esters previously isolated from bulk leaf extracts of various Eucalyptus species may also be localized within the non-volatile fraction of foliar secretory cavities.
pH Dependent Mechanisms of Hydrolysis of 4-Nitrophenyl β-D-Glucoside
Publisher: American Chemical Society (ACS)
Date: 09-02-2021
DOI: 10.26434/CHEMRXIV.13735084.V1
Abstract: 1,2- trans -Glycosides hydrolyze through a range of mechanisms under conditions of different pH, but systematic studies are lacking. Here we report the pH-rate constant profile for the hydrolysis of 4-nitrophenyl β-D-glucoside. An inverse kinetic isotope effect ( k (H 3 O + )/ k (D 3 O + ) = 0.63) in the acidic region indicates that the mechanism requires the formation of the conjugate acid of the substrate for the reaction to proceed, with heterolytic cleavage of the glycosidic C-O bond. Reactions in the pH-independent region extrapolated to zero buffer concentration show a small inverse solvent isotope effect k (H 2 O)/ k (D 2 O) = 1.1 and a positive entropy of activation (D S ‡ = 3.07 cal mol –1 K –1 ), which is consistent with water attack through a dissociative mechanism. In the basic region, solvolysis in 18 O-labelled water and H 2 O/MeOH mixtures allowed detection of bimolecular hydrolysis and neighboring group participation, and to a minor degree, nucleophilic aromatic substitution. Under mildly basic conditions, a bimolecular dissociative mechanism is implicated through a solvent isotope effect of k (HO - )/ k (DO - ) = 0.5 and a strongly negative entropy of activation (D S ‡ = –13.6 cal mol –1 K –1 ). Finally, at high pH, an inverse solvent isotope effect of k (HO - )/ k (DO - ) = 0.6 and a weakly negative entropy of activation (D S ‡ = –5.5 cal mol –1 K –1 ) indicates that the formation of 1,2-anhydrosugar is the rate determining step.
Nanomolar versus Millimolar Inhibition by Xylobiose-Derived Azasugars: Significant Differences between Two Structurally Distinct Xylanases
Publisher: American Chemical Society (ACS)
Date: 23-02-2000
DOI: 10.1021/JA993805J
Discovery of N‐Aryloxypropylbenzylamines as Voltage‐Gated Sodium Channel NaV1.2‐Subtype‐Selective Inhibitors
Publisher: Wiley
Date: 12-02-2019
Abstract: We previously reported that a lipophilic N-(4'-hydroxy-3',5'-di-tert-butylbenzyl) derivative (1) of the voltage-gated sodium channel blocker mexiletine, was a more potent sodium channel blocker in vitro and in vivo. We demonstrate that replacing the chiral methylethylene linker between the amine and di-tert-butylphenol with an achiral 1,3-propylene linker (to give (2)) maintains potency in vitro. We synthesized 25 analogues bearing the 1,3-propylene linker and found that minor structural changes resulted in pronounced changes in state dependence of blocking human Na
A practical synthesis of long-chain iso-fatty acids (iso-C12–C19) and related natural products
Publisher: Beilstein Institut
Date: 04-09-2013
DOI: 10.3762/BJOC.9.210
Abstract: A gram-scale synthesis of terminally-branched iso-fatty acids (iso-C 12 –C 19 ) was developed commencing with methyl undec-10-enoate (methyl undecylenate) (for iso-C 12 –C 14 ) or the C 15 and C 16 lactones pentadecanolide (for iso-C 15 –C 17 ) and hexadecanolide (for iso-C 18 –C 19 ). Central to the approaches outlined is the two-step construction of the terminal isopropyl group through addition of methylmagnesium bromide to the ester/lactones and selective reduction of the resulting tertiary alcohols. Thus, the C 12 , C 17 and C 18 iso-fatty acids were obtained in three steps from commercially-available starting materials, and the remaining C 13 –C 16 and C 19 iso-fatty acids were prepared by homologation or recursive dehomologations of these fatty acids or through intercepting appropriate intermediates. Highlighting the synthetic potential of the iso-fatty acids and various intermediates prepared herein, we describe the synthesis of the natural products ( S )-2,15-dimethylpalmitic acid, ( S )-2-hydroxy-15-methylpalmitic acid, and 2-oxo-14-methylpentadecane.
MCL and Mincle: C-Type Lectin Receptors That Sense Damaged Self and Pathogen-Associated Molecular Patterns
Publisher: Frontiers Media SA
Date: 23-06-2014
The Molecular Basis of Sulfosugar Selectivity in Sulfoglycolysis
Publisher: American Chemical Society (ACS)
Date: 09-02-2021
DOI: 10.26434/CHEMRXIV.12974237.V3
Abstract: The sulfosugar sulfoquinovose (SQ) is produced by essentially all photosynthetic organisms on earth and is metabolized by bacteria through the process of sulfoglycolysis. The sulfoglycolytic Embden-Meyerhof-Parnas pathway metabolises SQ to produce dihydroxyacetone phosphate and sulfolactaldehyde and is analogous to the classical Embden-Meyerhof-Parnas glycolysis pathway for the metabolism of glucose-6-phosphate, though the former only provides one C3 fragment to central metabolism, with excretion of the other C3 fragment as dihydroxypropanesulfonate. Here, we report a comprehensive structural and biochemical analysis of the three core steps of sulfoglycolysis catalyzed by SQ isomerase, sulfofructose (SF) kinase and sulfofructose-1-phosphate (SFP) aldolase. Our data shows that despite the superficial similarity of this pathway to glycolysis, the sulfoglycolytic enzymes are specific for SQ metabolites and are not catalytically active on related metabolites from glycolytic pathways. This observation is rationalized by 3D structures of each enzyme, which reveal the presence of conserved sulfonate-binding pockets. We show that SQ isomerase acts preferentially on the β-anomer of SQ and reversibly produces both SF and sulforhamnose (SR), a previously unknown sugar that acts as a transcriptional regulator for the transcriptional repressor CsqR that regulates SQ-utilization. We also demonstrate that SF kinase is a key regulatory enzyme for the pathway that experiences complex modulation by the metabolites AMP, ADP, ATP, F6P, FBP, PEP, and citrate, and we show that SFP aldolase reversibly synthesizes SFP. This body of work provides fresh insights into the mechanism, specificity and regulation of sulfoglycolysis and has important implications for understanding how this biochemistry interfaces with central metabolism in prokaryotes to process this major repository of biogeochemical sulfur.
The Molecular Basis of Sulfosugar Selectivity in Sulfoglycolysis
Publisher: American Chemical Society (ACS)
Date: 23-09-2020
DOI: 10.26434/CHEMRXIV.12974237.V2
Abstract: The sulfosugar sulfoquinovose (SQ) is produced by essentially all photosynthetic organisms on earth and is metabolized bacteria through the process of sulfoglycolysis. The sulfoglycolytic Embden-Meyerhof-Parnas pathway metabolises SQ to produce dihydroxyacetone phosphate and sulfolactaldehyde and is analogous to the classical Embden-Meyerhof-Parnas glycolysis pathway for the metabolism of glucose-6-phosphate, though the former only provides one C3 fragment to central metabolism, with excretion of the other C3 fragment as dihydroxypropanesulfonate. Here, we report a comprehensive structural and biochemical analysis of the three core steps of sulfoglycolysis catalyzed by SQ isomerase, sulfofructose (SF) kinase and sulfofructose-1-phosphate aldolase. Our data shows that despite the superficial similarity of this pathway to glycolysis, the sulfoglycolytic enzymes are specific for SQ metabolites and are not catalytically active on related metabolites from glycolytic pathways. This observation is rationalized by 3D structures of each of these enzymes, which reveal the presence of conserved sulfonate-binding pockets. We show that SQ isomerase acts preferentially on the b-anomer of SQ and reversibly produces both SF and sulforhamnose (SR), a previously unknown sugar that acts as a transcriptional regulator for the transcriptional repressor CsqR that regulates SQ-utilisation. We also demonstrate that SF kinase is a key regulatory enzyme for the pathway that experiences complex allosteric modulation by the metabolites AMP, ADP, ATP, F6P, FBP, PEP, and citrate. This body of work provides fresh insights into the mechanism, specificity and regulation of sulfoglycolysis and has important implications for understanding how this biochemistry interfaces with central metabolism in prokaryotes to process this major repository of biogeochemical sulfur.
The Molecular Basis of Sulfosugar Selectivity in Sulfoglycolysis
Publisher: American Chemical Society (ACS)
Date: 21-09-2020
DOI: 10.26434/CHEMRXIV.12974237.V1
Abstract: The sulfosugar sulfoquinovose (SQ) is produced by essentially all photosynthetic organisms on earth and is metabolized bacteria through the process of sulfoglycolysis. The sulfoglycolytic Embden-Meyerhof-Parnas pathway metabolises SQ to produce dihydroxyacetone phosphate and sulfolactaldehyde and is analogous to the classical Embden-Meyerhof-Parnas glycolysis pathway for the metabolism of glucose-6-phosphate, though the former only provides one C3 fragment to central metabolism, with excretion of the other C3 fragment as dihydroxypropanesulfonate. Here, we report a comprehensive structural and biochemical analysis of the three core steps of sulfoglycolysis catalyzed by SQ isomerase, sulfofructose (SF) kinase and sulfofructose-1-phosphate aldolase. Our data shows that despite the superficial similarity of this pathway to glycolysis, the sulfoglycolytic enzymes are specific for SQ metabolites and are not catalytically active on related metabolites from glycolytic pathways. This observation is rationalized by 3D structures of each of these enzymes, which reveal the presence of conserved sulfonate-binding pockets. We show that SQ isomerase acts preferentially on the b-anomer of SQ and reversibly produces both SF and sulforhamnose (SR), a previously unknown sugar that acts as a transcriptional regulator for the transcriptional repressor CsqR that regulates SQ-utilisation. We also demonstrate that SF kinase is a key regulatory enzyme for the pathway that experiences complex allosteric modulation by the metabolites AMP, ADP, ATP, F6P, FBP, PEP, and citrate. This body of work provides fresh insights into the mechanism, specificity and regulation of sulfoglycolysis and has important implications for understanding how this biochemistry interfaces with central metabolism in prokaryotes to process this major repository of biogeochemical sulfur.
A Family of Dual-Activity Glycosyltransferase-Phosphorylases Mediates Mannogen Turnover and Virulence in Leishmania Parasites
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.CHOM.2019.08.009
Abstract: Parasitic protists belonging to the genus Leishmania synthesize the non-canonical carbohydrate reserve, mannogen, which is composed of β-1,2-mannan oligosaccharides. Here, we identify a class of dual-activity mannosyltransferase hosphorylases (MTPs) that catalyze both the sugar nucleotide-dependent biosynthesis and phosphorolytic turnover of mannogen. Structural and phylogenic analysis shows that while the MTPs are structurally related to bacterial mannan phosphorylases, they constitute a distinct family of glycosyltransferases (GT108) that have likely been acquired by horizontal gene transfer from gram-positive bacteria. The seven MTPs catalyze the constitutive synthesis and turnover of mannogen. This metabolic rheostat protects obligate intracellular parasite stages from nutrient excess, and is essential for thermotolerance and parasite infectivity in the mammalian host. Our results suggest that the acquisition and expansion of the MTP family in Leishmania increased the metabolic flexibility of these protists and contributed to their capacity to colonize new host niches.
Mechanistic insights into a Ca2+-dependent family of α-mannosidases in a human gut symbiont
Publisher: Springer Science and Business Media LLC
Date: 27-12-2009
DOI: 10.1038/NCHEMBIO.278
A widespread family of oxidoreductive sulfoquinovosidases at the gateway to sulfoquinovose catabolism
Publisher: American Chemical Society (ACS)
Date: 09-10-2023
The carbohydrate-binding promiscuity of Euonymus europaeus lectin is predicted to involve a single binding site.
Publisher: Oxford University Press (OUP)
Date: 10-09-2015
Abstract: Euonymus europaeus lectin (EEL) is a carbohydrate-binding protein derived from the fruit of the European spindle tree. EEL was first identified for its erythrocyte agglutinating properties and specificity for B and H blood groups. However, a detailed molecular picture of the structural basis of carbohydrate recognition by EEL remains to be developed. In this study, we performed fluorescence titrations of a range of carbohydrates against EEL. Binding of EEL to a wide range of carbohydrates was observed, including a series of blood group-related carbohydrates, mannosides, chitotriose and sialic acid. Affinity was strongest for carbohydrates with H-related structures and the B trisaccharide. A homology model of EEL was produced from templates identified using the HHPred server, which employs hidden Markov models (HMMs) to identify templates. The HMM approach identified that the best templates for EEL were proteins featuring a ricin B-like (R-type) fold. Separate templates were used to model the core and binding site regions of the lectin. Through the use of constrained docking and spatial comparison with a template ligand, binding modes for the carbohydrate ligands were predicted. A relationship between the experimental binding energies and the computed binding energies of the selected docked poses was determined and optimized. Collectively, our results suggest that EEL utilizes a single site for recognition of carbohydrates terminating in a variety of monosaccharides.
Diazepam is not a direct allosteric modulator of α1-adrenoceptors, but modulates receptor signaling by inhibiting phosphodiesterase-4.
Publisher: Wiley
Date: 26-12-2018
DOI: 10.1002/PRP2.455
Chemistry and biology of the aminosulfonate cysteinolic acid: discovery, distribution, synthesis and metabolism
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2OB00362G
Abstract: This review provides an historical account of the poorly understood aminosulfonic acid d -cysteinolic acid. Its discovery, occurrence within marine organisms, routes for chemical synthesis, and speculation surrounding its metabolism are discussed.
A New, Simple, High-Affinity Glycosidase Inhibitor: Analysis of Binding through X-ray Crystallography, Mutagenesis, and Kinetic Analysis
Publisher: American Chemical Society (ACS)
Date: 14-04-2000
DOI: 10.1021/JA0002870
FT 23, an orally active antifibrotic compound, attenuates structural and functional abnormalities in an experimental model of diabetic cardiomyopathy
Publisher: Wiley
Date: 25-07-2012
DOI: 10.1111/J.1440-1681.2012.05726.X
Abstract: Diabetic cardiomyopathy is characterized by early diastolic dysfunction and structural changes, such as interstitial fibrosis and cardiac hypertrophy. Using the Ren-2 rat model, we sought to investigate the effect of FT23 on the structural and functional changes associated with diabetic cardiomyopathy. Heterozygous Ren-2 rats were rendered diabetic with streptozotocin by tail vein injection. Rats were then treated with FT23 (200 mg/kg per day by gavage twice daily) or vehicle from Week 8 to Week 16 after the onset of diabetes. Echocardiography was performed to assess heart function before the rats were killed and their hearts collected for histological and molecular biological assessment. The antifibrotic effect of FT23 was compared with that of tranilast in neonatal cardiac fibroblasts when stimulated with transforming growth factor (TGF)-β (5 ng/mL) at 30, 50 and 100 umol/L. FT23 exhibited greater inhibition of TGF-β-induced collagen production in neonatal cardiac fibroblasts, as measured by a [(3) H]-proline incorporation assay, compared with its parental compound tranilast. In the in vivo study, FT23 significantly attenuated the increased heart weight : bodyweight ratio in FT23-treated diabetic Ren-2 rats. Diastolic dysfunction, as measured by mitral valve (MV) E/A ratio and MV deceleration time, was also significantly attenuated by FT23. Picrosirius red-stained heart sections revealed that cardiac fibrosis in the diabetic rats was reduced by FT23 compared with that in vehicle-treated rats, with a concomitant reduction in collagen I immunostaining and infiltration of macrophages, as demonstrated by ED1 immunostaining. The results of the present study suggest that FT23 inhibits the activity of TGF-β and attenuates structural and functional manifestations of diastolic dysfunction observed in a model of diabetic cardiomyopathy.
The Synthesis of 1,4-anhydro-α-D-Mannopyranose
Publisher: American Chemical Society (ACS)
Date: 05-09-2018
DOI: 10.26434/CHEMRXIV.7040324.V1
Abstract: Manuscript describing efforts, ultimately successful, to synthesize 1,4-anhydromannose. Full experimental details and spectroscopic characterization.
Structure of human endo-α-1,2-mannosidase (MANEA), an antiviral host-glycosylation target
Publisher: Proceedings of the National Academy of Sciences
Date: 05-11-2020
Abstract: The glycosylation of proteins is a major protein modification that occurs extensively in eukaryotes. Glycosidases in the secretory pathway that trim N-linked glycans play key roles in protein quality control and in the specific modifications leading to mature glycoproteins. Inhibition of glucosidases in the secretory pathway is a proven therapeutic strategy, that holds great promise in the treatment of viral disease. The enzyme endo-α-1,2-mannosidase (MANEA) provides an alternative processing pathway to evade glucosidase inhibitors. We report the three-dimensional structure of human MANEA and complexes with enzyme inhibitors that we show act as antivirals for bovine viral diarrhea and human dengue viruses. The structure of MANEA will support inhibitor optimization and the development of more potent antivirals.
Total synthesis and mass spectrometric analysis of a Mycobacterium tuberculosis phosphatidylglycerol featuring a two-step synthesis of (R)-tuberculostearic acid
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7OB01786C
Abstract: A two-step synthesis of ( R )-tuberculostearic acid enables the total synthesis of a Mycobacterium tuberculosis phosphatidylglycerol. Mass spectrometric fragmentation of synthetic PG regioisomers of acylation patterns.
Synthesis of a hypoxia-targeted conjugate of the cardioprotective agent 3′,4′-dihydroxyflavonol and evaluation of its ability to reduce ischaemia/reperfusion injury
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.BMCL.2011.03.040
Abstract: 3',4'-Dihydroxyflavonol (DiOHF) is a cardioprotective flavonol that reduces injury associated with myocardial ischaemia and reperfusion. We hypothesized that the efficacy of DiOHF could be enhanced through its targeting to hypoxic regions of partial reperfusion. Copper(I)-catalyzed ligation of an azide-modified DiOHF analogue to 2-propargyl-nitroimidazole afforded a DiOHF-nitroimidazole conjugate (DiOHF-NIm). When incubated with Con8 cells under normoxic conditions DiOHF-NIm could be detected in both the culture supernatant and cell lysate, whereas under hypoxic conditions it was present in substantially reduced amounts consistent with its selective metabolism under hypoxia. DiOHF-NIm possessed antioxidant activity comparable to DiOHF through scavenging of superoxide produced by NADPH/NADPH oxidase, but had significantly attenuated vasorelaxant activity. DiOHF-NIm treatment significantly reduced lactate dehydrogenase release following ischaemia/reperfusion in hindlimbs of anaesthetized rats (p <0.05), to a level similar to DiOHF treatment but also at earlier time points. DiOHF-NIm significantly reduced levels of myeloperoxidase (p <0.05), a biomarker of neutrophil accumulation, whereas the reduction afforded by DiOHF was not significant. DiOHF-NIm therefore represents a promising potential therapeutic for ischaemia/reperfusion injury.
Chronic Brain Inflammation: The Neurochemical Basis for Drugs to Reduce Inflammation
Publisher: Springer Science and Business Media LLC
Date: 16-07-2015
DOI: 10.1007/S11064-015-1661-7
Abstract: It is now recognised that the brain and the peripheral immune system have bidirectional communication in both health and neuronal diseases. Brain inflammation results after both acute injury and also with the appearance of mutated proteins or endogenous neurotoxic metabolites associated with slow neurodegenerative diseases such as Alzheimer's and Parkinson's diseases and some psychiatric disorders. Microglia play a key role in brain inflammation by the release of pro-inflammatory cytokines and with ageing, microglia exhibit 'priming' leading to increased basal release of the pro-inflammatory cytokines. Neurochemical targets to reduce or slow chronic brain inflammation include cyclooxygenase enzymes, Nrf2 transcription factor, angiotensin AT1 receptors and sigma-1 receptors. Development of more selective drugs to act at these targets is occurring but large scale clinical trials to validate the drugs will take significant time.
Design of potent Mincle signalling agonists based on an alkyl β-glucoside template
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CC00670J
Abstract: Potent signalling agonists of the innate immune receptor Mincle were developed that can be easily prepared from the surfactants octyl and lauryl β- d -glucoside.
Ground state structures of sulfate monoesters and sulfamates reveal similar reaction coordinates for sulfuryl and sulfamyl transfer
Publisher: Royal Society of Chemistry (RSC)
Date: 2006
DOI: 10.1039/B513712H
Abstract: Structure/reactivity and structure/structure correlations of 5 sulfate monoesters and 11 sulfamate esters determined by low temperature X-ray crystallography reveal similar ground state deformations that suggest similar reaction coordinates for sulfuryl and sulfamyl group transfer.
Human gut Bacteroidetes can utilize yeast mannan through a selfish mechanism
Publisher: Springer Science and Business Media LLC
Date: 07-01-2015
DOI: 10.1038/NATURE13995
Peptides and Proteins by Shawn Doonan
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/CH00315_BR
Identification of levoglucosan degradation pathways in bacteria and sequence similarity network analysis
Publisher: Cold Spring Harbor Laboratory
Date: 29-01-2023
DOI: 10.1101/2023.01.28.526070
Abstract: Levoglucosan is produced in the pyrolysis of cellulose and starch, including from bushfires or the burning of biofuels, and is deposited from the atmosphere across the surface of the earth. We describe two levoglucosan degrading Paenarthrobacter spp. ( Paenarthrobacter nitrojuajacolis LG01 and Paenarthrobacter histidinolovorans LG02) that were isolated from soil by metabolic enrichment using levoglucosan as the sole carbon source. Genome sequencing and proteomics analysis revealed the expression of a series of genes encoding known levoglucosan degrading enzymes, levoglucosan dehydrogenase (LGDH, LgdA), 3-keto-levoglucosan β-eliminase (LgdB1) and glucose 3-dehydrogenase (LgdC), along with an ABC transporter cassette and an associated solute binding protein. However, no homologues of 3-ketoglucose dehydratase (LgdB2) were evident, while the expressed genes contained a range of putative sugar phosphate isomerases/xylose isomerases with weak similarity to LgdB2. Sequence similarity network analysis of genome neighbours of LgdA revealed that homologues of LgdB1 and LgdC are generally conserved in a range of bacteria in the phyla Firmicutes, Actinobacteria and Proteobacteria. One group of sugar phosphate isomerase/xylose isomerase homologues (named LgdB3) was identified with limited distribution that is mutually exclusive with LgdB2, and we propose that they may fulfill a similar function. LgdB1, LgdB2 and LgdB3 adopt similar predicted 3D folds, suggesting overlapping function in processing intermediates in LG metabolism. Our findings highlight ersity within the LGDH pathway, through which bacteria utilize levoglucosan as a nutrient source.
Chemical approaches for the study of the mycobacterial glycolipids phosphatidylinositol mannosides, lipomannan and lipoarabinomannan
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C000604A
Remodelling of carbon metabolism during sulfoglycolysis in Escherichia coli
Publisher: Cold Spring Harbor Laboratory
Date: 10-09-2022
DOI: 10.1101/2022.09.09.507388
Abstract: Sulfoquinovose (SQ) is a major metabolite in the global sulfur cycle produced by nearly all photosynthetic organisms. One of the major pathways involved in the catabolism of SQ in bacteria, such as Escherichia coli , is a variant of the glycolytic Embden-Meyerhof-Parnas (EMP) pathway termed the sulfoglycolytic EMP (sulfo-EMP) pathway, which leads to consumption of three of the six carbons of SQ and excretion of 2,3-dihydroxypropanesulfonate (DHPS). Comparative metabolite profiling of aerobically Glc-grown and SQ-grown E. coli was undertaken to identify the metabolic consequences of switching from glycolysis to sulfoglycolysis. Sulfoglycolysis was associated with the ersion of triose-phosphates to synthesize sugar phosphates (gluconeogenesis), and an unexpected accumulation of trehalose and glycogen storage carbohydrates. Sulfoglycolysis was also associated with global changes in central carbon metabolism, as indicated by changes in levels of intermediates in the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway (PPP), polyamine metabolism, pyrimidine metabolism and many amino acid metabolic pathways. Upon entry into stationary phase and depletion of SQ, E. coli utilize their glycogen, indicating a reversal of metabolic fluxes to allow glycolytic metabolism. The sulfosugar sulfoquinovose is estimated to be produced on a scale of 10 billion tonnes per annum, making it a major organosulfur species in the biosulfur cycle. Microbial degradation of sulfoquinovose through sulfoglycolysis allows utilization of its carbon content and contributes to biomineralization of its sulfur. However, the metabolic consequences of microbial growth on sulfoquinovose are unclear. We use metabolomics to identify the metabolic adaptations that Escherichia coli undergoes when grown on sulfoquinovose versus glucose. This revealed increased flux into storage carbohydrates through gluconeogenesis, and reduced flux of carbon into the TCA cycle and downstream metabolism. These changes are relieved upon return to stationary phase growth and reversion to glycolytic metabolism. This work provides s new insights into the metabolic consequences of microbial growth on an abundant sulfosugar.
Benzofuran sulfonates and small self-lipid antigens activate type II NKT cells via CD1d
Publisher: Proceedings of the National Academy of Sciences
Date: 20-08-2021
Abstract: Whereas T cells are known to recognize peptides, vitamin B metabolites, or lipid antigens, we identify several nonlipidic small molecules classified as pentamethylbenzofuransulfonates (PBFs) that activate a population of CD1d-restricted natural killer T (NKT) cells. This represents a breakthrough in the field of NKT cell biology. This study also reveals a previously unknown population of PBF-reactive NKT cells in healthy in iduals with stereotyped receptors that paves the way for future studies of the role of these cells in immunity, including sulfa drug hypersensitivity.
Aspartate 313 in the Streptomyces plicatusHexosaminidase Plays a Critical Role in Substrate-assisted Catalysis by Orienting the 2-Acetamido Group and Stabilizing the Transition State
Publisher: Elsevier BV
Date: 10-2002
Carbohydrate-active enzymes: sequences, shapes, contortions and cells
Publisher: Portland Press Ltd.
Date: 09-02-2016
DOI: 10.1042/BST20150186
Abstract: The enzyme-catalysed degradation of oligo and polysaccharides is of considerable interest in many fields ranging from the fundamental–understanding the intrinsic chemical beauty–through to the applied, including erse practical applications in medicine and biotechnology. Carbohydrates are the most stereochemically-complex biopolymer, and myriad different natural polysaccharides have led to evolution of multifaceted enzyme consortia for their degradation. The glycosidic bonds that link sugar monomers are among the most chemically-stable, yet enzymatically-labile, bonds in the biosphere. That glycoside hydrolases can achieve a rate enhancement (kcat/kuncat) & -fold provides testament to their remarkable proficiency and the sophistication of their catalysis reaction mechanisms. The last two decades have seen significant advances in the discovery of new glycosidase sequences, sequence-based classification into families and clans, 3D structures and reaction mechanisms, providing new insights into enzymatic catalysis. New impetus to these studies has been provided by the challenges inherent in plant and microbial polysaccharide degradation, both in the context of environmentally-sustainable routes to foods and biofuels, and increasingly in human nutrition. Study of the reaction mechanism of glycoside hydrolases has also inspired the development of enzyme inhibitors, both as mechanistic probes and increasingly as therapeutic agents. We are on the cusp of a new era where we are learning how to dovetail powerful computational techniques with structural and kinetic data to provide an unprecedented view of conformational details of enzyme action.
Transition-State Mimicry by Glycosidase Inhibitors: A Critical Kinetic Analysis
Publisher: American Chemical Society (ACS)
Date: 27-03-2007
DOI: 10.1021/JA0707254
Aryl sulfamates are broad spectrum inactivators of sulfatases: Effects on sulfatases from various sources
Publisher: Elsevier BV
Date: 2009
DOI: 10.1016/J.BMCL.2008.11.059
Abstract: Aryl sulfamates were originally developed as inhibitors of steroid sulfatase, and have recently been shown to be powerful inactivators of a bacterial sulfatase, PaAtsA from Pseudomonas aeruginosa. We demonstrate that a simple aryl sulfamate, 3-nitrophenyl sulfamate, can inactivate sulfatases from various sources including snail, limpet and abalone. In each case inactivation was time-dependent and active-site directed, as demonstrated by protection against inactivation by substrate. These results suggest that such easily acquired aryl sulfamates can be used as reliable biochemical reagents for the study of sulfatases from a erse array of sources.
A master of its sulfate
Publisher: Springer Science and Business Media LLC
Date: 08-2004
DOI: 10.1038/NSMB0804-686
Comprehensive Synthesis of Substrates, Intermediates, and Products of the Sulfoglycolytic Embden-Meyerhoff-Parnas Pathway.
Publisher: American Chemical Society (ACS)
Date: 11-02-2019
Abstract: Sulfoglycolysis is a metabolic pathway dedicated to the catabolism of the sulfosugar sulfoquinovose (SQ) into smaller organosulfur fragments. An estimated 10 billion tonnes of SQ fluxes through sulfoglycolysis pathways each year, making it a significant aspect of the biogeochemical sulfur cycle. Delineating the molecular details of sulfoglycolysis requires authentic s les of the various metabolites in these pathways. To this end, we have established chemical and chemoenzymatic methods for the synthesis of the key organosulfur metabolites sulfoquinovosylglycerol, SQ (also in
Quantitation in the regioselectivity of acylation of glycosyl diglycerides: total synthesis of a Streptococcus pneumoniae α-glucosyl diglyceride
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C6CC09584D
Abstract: Regioselective fidelity of acylation of glycosyl diacylglycerols can be monitored by use of isotope-labelled fatty acids and quantitative 13 C NMR spectroscopy.
Distinct CD1d docking strategies exhibited by diverse Type II NKT cell receptors
Publisher: Springer Science and Business Media LLC
Date: 20-11-2019
DOI: 10.1038/S41467-019-12941-9
Abstract: Type I and type II natural killer T (NKT) cells are restricted to the lipid antigen-presenting molecule CD1d. While we have an understanding of the antigen reactivity and function of type I NKT cells, our knowledge of type II NKT cells in health and disease remains unclear. Here we describe a population of type II NKT cells that recognise and respond to the microbial antigen, α-glucuronosyl-diacylglycerol (α-GlcADAG) presented by CD1d, but not the prototypical type I NKT cell agonist, α-galactosylceramide. Surprisingly, the crystal structure of a type II NKT TCR-CD1d-α-GlcADAG complex reveals a CD1d F’-pocket-docking mode that contrasts sharply with the previously determined A’-roof positioning of a sulfatide-reactive type II NKT TCR. Our data also suggest that erse type II NKT TCRs directed against distinct microbial or mammalian lipid antigens adopt multiple recognition strategies on CD1d, thereby maximising the potential for type II NKT cells to detect different lipid antigens.
Total synthesis of a cyclopropane-fatty acid α-glucosyl diglyceride from Lactobacillus plantarum and identification of its ability to signal through Mincle
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CC05631H
Abstract: Total synthesis of GL1, a complex unsaturated, cyclopropane-containing glycolipid from Lactobacillus plantarum was accomplished. GL1 and analogues were shown to signal through mouse and human Mincle.
Trifluoromethanesulfonic Anhydride
Publisher: John Wiley & Sons, Ltd
Date: 15-04-2004
Acetylation of Trehalose Mycolates Is Required for Efficient MmpL-Mediated Membrane Transport in Corynebacterineae
Publisher: American Chemical Society (ACS)
Date: 08-12-2014
DOI: 10.1021/CB5007689
Abstract: Pathogenic species of Mycobacteria and Corynebacteria, including Mycobacterium tuberculosis and Corynebacterium diphtheriae, synthesize complex cell walls that are rich in very long-chain mycolic acids. These fatty acids are synthesized on the inner leaflet of the cell membrane and are subsequently transported to the periplasmic space as trehalose monomycolates (TMM), where they are conjugated to other cell wall components and to TMM to form trehalose dimycolates (TDM). Mycobacterial TMM, and the equivalent Corynebacterium glutamicum trehalose corynomycolates (TMCM), are transported across the inner membrane by MmpL3, or NCgl0228 and NCgl2769, respectively, although little is known about how this process is regulated. Here, we show that transient acetylation of the mycolyl moiety of TMCM is required for periplasmic export. A bioinformatic search identified a gene in a cell wall biosynthesis locus encoding a putative acetyltransferase (M. tuberculosis Rv0228/C. glutamicum NCgl2759) that was highly conserved in all sequenced Corynebacterineae. Deletion of C. glutamicum NCgl2759 resulted in the accumulation of TMCM, with a concomitant reduction in surface transport of this glycolipid and syntheses of cell wall trehalose dicorynomycolates. Strikingly, loss of NCgl2759 was associated with a defect in the synthesis of a minor, and previously uncharacterized, glycolipid species. This lipid was identified as trehalose monoacetylcorynomycolate (AcTMCM) by mass spectrometry and chemical synthesis of the authentic standard. The in vitro synthesis of AcTMCM was dependent on acetyl-CoA, whereas in vivo [(14)C]-acetate pulse-chase labeling showed that this lipid was rapidly synthesized and turned over in wild-type and genetically complemented bacterial strains. Significantly, the biochemical and TMCM/TDCM transport phenotype observed in the ΔNCgl2759 mutant was phenocopied by inhibition of the activities of the two C. glutamicum MmpL3 homologues. Collectively, these data suggest that NCgl2759 is a novel TMCM mycolyl acetyltransferase (TmaT) that regulates transport of TMCM and is a potential drug target in pathogenic species.
Glycolipids from the gut symbiont Bacteroides fragilis are agonists for natural killer T cells and induce their regulatory differentiation
Publisher: American Chemical Society (ACS)
Date: 23-05-2023
DOI: 10.26434/CHEMRXIV-2023-XBJD0-V2
Abstract: Natural Killer T (NKT) cells are a lipid-antigen reactive, CD1d-restricted T cell subset with erse functional properties that contribute to inflammatory and regulatory immune responses. The most studied lipid antigen target for these cells is alpha-galactosylceramide (GC). The commensal organism Bacteroides fragilis (B. fragilis) produces several forms of GC, but conflicting information exists about the influence of these lipids on NKT cells. Herein, we report the total synthesis of a major form of alpha-GC from B. fragilis (Bf alpha-GC), and several analogues thereof. We confirm the T cell receptor (TCR)-mediated recognition of these glycolipids by mouse and human NKT cells. Despite the natural structure of Bf alpha-GC containing lipid branching that limits potency, we demonstrate that Bf alpha-GC drives mouse NKT cells to proliferate and differentiate into producers of the immunoregulatory cytokine, interleukin-10 (IL-10). These Bf alpha-GC-experienced NKT cells display regulatory function by inhibiting the expansion of naïve NKT cells upon subsequent exposure to this antigen. Moreover, this regulatory activity impacts more than just NKT cells, as demonstrated by the NKT cell-mediated inhibition of antigen-stimulated mucosal-associated invariant T (MAIT) cells. These findings reveal that B. fragilis-derived NKT cell agonists may have broad immunoregulatory activity, providing insight into the mechanisms influencing immune tolerance to commensal bacteria and highlighting a potential means to manipulate NKT cell function for therapeutic benefit.
A carbon tetrachloride-free synthesis of N -phenyltrifluoroacetimidoyl chloride
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.CARRES.2017.08.004
Abstract: N-Phenyltrifluoroacetimidoyl chloride (PTFAI-Cl) is a reagent widely used for the preparation of glycosyl N-phenyltrifluoroacetimidates. However, the most commonly applied method requires carbon tetrachloride, a hepatotoxic reagent that has been phased out under the Montreal Protocol. We report a new synthesis of N-phenyltrifluoroacetimidoyl chloride (PTFAI-Cl) using dichlorotriphenylphosphane and triethylamine.
α-Glucuronosyl and α-Glucosyl Diacylglycerides, Natural Killer T Cell-Activating Lipids from Bacteria and Fungi
Publisher: American Chemical Society (ACS)
Date: 21-10-2019
DOI: 10.26434/CHEMRXIV.9746033
Abstract: Natural killer T cells express T cell receptors (TCRs) that recognize glycolipid antigens in association with the antigen-presenting molecule CD1d. Here, we report the concise chemical synthesis of a range of saturated and unsaturated α-glucosyl and α-glucuronosyl diacylglycerides of bacterial and fungal origins from allyl α-glucoside with Jacobsen kinetic resolution as a key step. We show that these glycolipids could be recognized by a classical type I NKT TCR that uses an invariant Vα14-Jα18 TCR α-chain, but also by an atypical NKT TCR that uses a different TCR α-chain (Vα10-Jα50). In both cases, recognition was sensitive to the lipid fine structure, and included recognition of glycosyl diacylglycerides bearing branched (R- and S-tuberculostearic acid) and unsaturated (oleic and vaccenic) acids. The TCR footprints on CD1d-loaded with a mycobacterial α-glucuronosyl diacylglyceride was assessed using mutant CD1d molecules and, while similar to that for α-GalCer recognition by a type I NKT TCR, were more sensitive to mutations when α-glucuronosyl diacylglyceride was the antigen. In summary, we provide an efficient approach for synthesis of a broad class of bacterial and fungal α-glycosyl diacylglyceride antigens and demonstrate that they can be recognised by TCRs derived from type I and atypical NKT cells.
'Click' Preparation of Carbohydrate 1-Benzotriazoles, 1,4-Disubstituted, and 1,4,5-Trisubstituted Triazoles and their Utility as Glycosyl Donors
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/CH08364
Abstract: Glycosyl triazoles can be prepared from readily available anomeric azides through various ‘click’ methodologies: thermal Huisgen cycloaddition with alkynes, strain-promoted Huisgen cycloaddition of benzynes, and CuI-catalyzed azide-alkyne cycloaddition of terminal alkynes (CuAAC reaction). Here we investigate the formation of glycosyl 1-benzotriazoles from anomeric and non-anomeric carbohydrate azides using benzynes derived from substituted anthranilic acids. The reactivity of the resulting anomeric 1-benzotriazoles as glycosyl donors was investigated and compared with 1,4-disubstituted glycosyl triazoles (from the CuAAC reaction) and 1,4,5-trisubstituted glycosyl triazoles (prepared by Huisgen cycloaddition of glycosyl azides and dimethyl acetylene dicarboxylate). The 1,4,5-trisubstituted glycosyl triazoles were activated by Lewis acids and could be converted to O-glycosides, S-glycosides, glycosyl chlorides, and glycosyl azides. By contrast, under all conditions investigated, the 1,4-disubstituted glycosyl triazoles were unreactive as glycosyl donors. Glycosyl 1-benzotriazoles were generally inert as glycosyl donors however, a tetrafluorobenzotriazole derivative, which bears electron-withdrawing substituents on the benzotriazole group, was a moderate glycosyl donor and could be converted to an S-glycoside by treatment with thiocresol and tin(iv) chloride.
Unimolecular, Bimolecular, and Intramolecular Hydrolysis Mechanisms of 4-Nitrophenyl β-d -Glucopyranoside
Publisher: American Chemical Society (ACS)
Date: 30-06-2021
Sulfoglycolysis: catabolic pathways for metabolism of sulfoquinovose
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1CS00846C
Abstract: A biochemical, structural and mechanistic perspective on the pathways of sulfoglycolysis for catabolism of the sulfosugar sulfoquinovose.
Structure of human endo-α-1,2-mannosidase (MANEA), an antiviral host-glycosylation target
Publisher: Cold Spring Harbor Laboratory
Date: 07-2020
DOI: 10.1101/2020.06.30.179523
Abstract: Mammalian protein N - linked glycosylation is critical for glycoprotein folding, quality control, trafficking, recognition and function. N - linked glycans are synthesized from Glc 3 Man 9 GlcNAc 2 precursors that are trimmed and modified in the endoplasmic reticulum (ER) and Golgi apparatus by glycoside hydrolases and glycosyltransferases. Endo-α-1,2-mannosidase (MANEA) is the sole endo -acting glycoside hydrolase involved in N - glycan trimming and unusually is located within the Golgi, where it allows ER escaped glycoproteins to bypass the classical N - glycosylation trimming pathway involving ER glucosidases I and II. There is considerable interest in the use of small molecules that disrupt N-linked glycosylation as therapeutic agents for diseases such as cancer and viral infection. Here we report the structure of the catalytic domain of human MANEA and complexes with substrate-derived inhibitors, which provide insight into dynamic loop movements that occur upon substrate binding. We reveal structural features of the human enzyme that explain its substrate preference and the mechanistic basis for catalysis. The structures inspired the development of new inhibitors that disrupted host protein N - glycan processing of viral glycans and reduced infectivity of bovine viral diarrhea and dengue viruses in cellular models. These results may contribute to efforts of developing broad-spectrum antiviral agents and bring about a more detailed view of the biology of mammalian glycosylation. The glycosylation of proteins is a major protein modification that occurs extensively in eukaryotes. Glycosidases in the secretory pathway that trim N-linked glycans play a key role in protein quality control and in the specific modifications leading to mature glycoproteins. Inhibition of glucosidases in the secretory pathway is a proven therapeutic strategy, and one with great promise in the treatment of viral disease. The enzyme endo-α-1,2-mannosidase, MANEA, provides an alternative processing pathway to evade glucosidase inhibitors. We report the 3D structure of human MANEA and complexes with enzyme inhibitors that we show act as antivirals for bovine viral diarrhea and human dengue viruses. The structure of MANEA will support inhibitor optimization and the development of more potent antivirals.
A convenient gram-scale synthesis of uridine diphospho(13C6)glucose
Publisher: Elsevier BV
Date: 07-2006
DOI: 10.1016/J.CARRES.2006.02.033
Abstract: A simple gram-scale synthesis of uridine diphospho(13C6)glucose is presented from D-(13C6)glucose. The critical step uses a 1H-tetrazole-catalyzed coupling of 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl-1-phosphate and UMP-morpholidate. The uridine diphospho(13C6)glucose was used in the structural identification of (1-->3)-beta-D-glucan from Lolium multiflorum.
Synthesis and evaluation of dithiolethiones as novel cyclooxygenase inhibitors
Publisher: Elsevier BV
Date: 2009
DOI: 10.1016/J.BMCL.2008.11.045
Abstract: 3H-1,2-Dithiole-3-thiones substituted with a 3,5-di-tert-butyl-4-hydroxyphenyl (DTBHP) or a 3,5-di-tert-butyl-4-methoxyphenyl group at the C5 position were prepared and their ability to inhibit the cyclooxygenase isoenzymes, COX-1 and COX-2 was evaluated. Both compounds were potent inhibitors of COX-2 (relative to rofecoxib), and while the phenol was a weak inhibitor of COX-1, the methyl ether gave no measurable inhibition. Docking studies of the two compounds into the COX-1 and -2 active sites showed that the methyl ether could only fit in the COX-2 active site whereas the phenol could be docked into both COX-1 and -2. This study reports a new mode for inhibitor binding to COX-1 and -2 and a novel structural scaffold for the development of COX-2 selective inhibitors.
Synthesis of Sulfoquinovose and Sulfoquinovosyl Diacylglycerides, and a Fluorogenic Substrate for Sulfoquinovosidases
Publisher: American Chemical Society (ACS)
Date: 02-12-2019
DOI: 10.26434/CHEMRXIV.10566101
Abstract: The sulfolipid sulfoquinovosyl diacylglycerol (SQDG) and its headgroup, the sulfosugar sulfoquinovose (SQ), are estimated to harbour up to half of all organosulfur in the biosphere. SQ is liberated from SQDG and related glycosides by the action of sulfoquinovosidases (SQases). We report a 10-step synthesis of SQDG that we apply to the preparation of saturated and unsaturated lipoforms. We also report an expeditious synthesis of SQ and ( sup /sup C sub /sub )SQ, and X-ray crystal structures of sodium and potassium salts of SQ. Finally, we report the synthesis of a fluorogenic SQase substrate, methylumbelliferyl a-D-sulfoquinovoside, and examination of its cleavage kinetics by two recombinant SQases.
The metabolic repair enzyme phosphoglycolate phosphatase regulates central carbon metabolism and fosmidomycin sensitivity inPlasmodium falciparum
Publisher: Cold Spring Harbor Laboratory
Date: 12-09-2018
DOI: 10.1101/415505
Abstract: The asexual blood stages of the malaria parasite, Plasmodium falciparum are highly dependent on glycolysis for ATP synthesis, redox balance and provision of essential anabolic precursors. Recent studies have suggested that members of the haloacid dehalogenase (HAD) family of metabolite phosphatases may play an important role in regulating multiple pathways in P. falciparum central carbon metabolism. Here, we show that the P. falciparum HAD protein, phosphoglycolate phosphatase ( Pf PGP), which is homologous to yeast Pho13 and mammalian PGP, regulates glycolysis in asexual blood stages by controlling intracellular levels of several intermediates and novel end-products of this pathway. Deletion of the P. falciparum pgp gene significantly attenuated asexual parasite growth in red blood cells, while comprehensive metabolomic analysis revealed the accumulation of two previously uncharacterized metabolites, as well as changes in a number of intermediates in glycolysis and the pentose phosphate pathway. The two unknown metabolites were assigned as 2-phospho-lactate and 4-phosphoerythronate by comparison of their mass spectra with synthetic standards. 2-Phospho-lactate was significantly elevated in wildtype and Δ Pf PGP parasites cultivated in the presence of methylglyoxal and D-lactate, but not L-lactate, indicating that it is a novel end-product of the methylglyoxal pathway. 4-Phosphoerythronate is a putative side product of the glycolytic enzyme, glyceraldehyde dehydrogenase and the accumulation of both 4-phosphoerythronate and 2-phospho-D-lactate were associated with changes in glycolytic and the pentose phosphate pathway fluxes as shown by 13 C-glucose labelling studies and increased sensitivity of the Δ Pf PGP parasites to the drug fosmidomycin. Our results suggest that Pf PGP contributes to a novel futile metabolic cycle involving the phosphorylation/dephosphorylation of D-lactate as well as detoxification of metabolites, such as 4-phosphoerythronate, and both may have important roles in regulating P. falciparum central carbon metabolism. The major pathogenic stages of the malaria parasite, Plasmodium falciparum , develop in red blood cells where they have access to an abundant supply of glucose. Unsurprisingly these parasite stages are addicted to using glucose, which is catabolized in the glycolytic and the pentose phosphate pathways. While these pathways also exist in host cells, there is increasing evidence that P. falciparum has evolved novel ways for regulating glucose metabolism that could be targeted by next-generation of anti-malarial drugs. In this study, we show the red blood cell stages of P. falciparum express an enzyme that is specifically involved in regulating the intracellular levels of two metabolites that are novel end-products or side products of glycolysis. Parasite mutants lacking this enzyme are viable but exhibit diminished growth rates in red blood cells. These mutant lines accumulate the two metabolites, and exhibit global changes in central carbon metabolism. Our findings suggest that metabolic end/side products of glycolysis directly regulate the metabolism of these parasites, and that the intracellular levels of these are tightly controlled by previously uncharacterized metabolite phosphatases.
Synthesis of the Alkylsulfonate Metabolites Cysteinolic Acid, 3-Amino-2-hydroxypropanesulfonate, and 2,3-Dihydroxypropanesulfonate
Publisher: American Chemical Society (ACS)
Date: 24-02-2022
Abstract: Chiral hydroxy- and aminohydroxysulfonic acids are widespread in the marine and terrestrial environment. Here we report simple methods for the synthesis of d- and l-cysteinolic acid (from (Boc-d-Cys-OH)
Molecular Basis of Sulfosugar Selectivity in Sulfoglycolysis
Publisher: American Chemical Society (ACS)
Date: 23-02-2021
Electronic Structure of the Sulfonyl and Phosphonyl Groups: A Computational and Crystallographic Study
Publisher: American Chemical Society (ACS)
Date: 19-09-2007
DOI: 10.1021/IC700687T
Abstract: A computational and X-ray crystallographic investigation of the electronic and geometric structures of a range of sulfonyl (-SO(2)-) and phosphonyl (-PO(2)--) containing species was undertaken to investigate the nature of valency and bonding in these functional groups. The traditional representation of sulfonyl and phosphonyl species is with octet-violating Lewis structures, which require d-orbital participation at the central atom. However, computational studies cast serious doubt upon this bonding model. In this work, we have employed NBO/NRT analysis to investigate hybridization, atomic formal charges, donor-acceptor interactions, and resonance structure contributions. Our results predict that within sulfonyl and phosphonyl systems, bonding interactions are highly polarized, of the form X+-Y- (X = P, S), and possess additional contributions from reciprocal n --> sigma* interactions where substituents off sulfur or phosphorus simultaneously act as donors and acceptors. Experimental evidence for the proposed bonding arrangement is provided for the sulfonyl functional group through a series of low-temperature X-ray structure correlations for sulfate monoesters, sulfamates, and methanesulfonates. Examination of changes to bond lengths and geometries upon substituent variation support the computational results. Together, our studies lend support for a bonding network in sulfonyl and phosphonyl groups composed of polar interactions augmented with reciprocal hyperconjugative bonding, which does not necessitate significant d-orbital participation nor formal octet violation at the central sulfur or phosphorus.
A new anti-fibrotic drug attenuates cardiac remodeling and systolic dysfunction following experimental myocardial infarction
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.IJCARD.2012.11.067
Abstract: Pathological deposition of extracellular matrix in the non-infarct zone (NIZ) of the ventricle post myocardial infarction (MI) is a key contributor to cardiac remodeling and heart failure. FT011, a novel antifibrotic compound, was evaluated for its efficacy in neonatal cardiac fibroblasts (NCF) and in an experimental MI model. Collagen synthesis in NCF was determined by (3)H-proline incorporation following stimulation with TGF-β or angiotensin II (Ang II). FT011 inhibited collagen synthesis to both agents in a dose dependent manner. In vivo, Sprague Dawley rats underwent left anterior descending coronary artery ligation or sham surgery and were randomized one week later to receive either FT011 (200mg/kg/day) or vehicle for a further 4 weeks. Echocardiography and cardiac catheterization were performed, and tissues were collected for histological analysis of collagen, myocyte hypertrophy, interstitial macrophage accumulation and Smad2 phosphorylation. mRNA expression of collagens I and III and TGF-β was measured using in situ hybridization and RT-PCR, respectively. FT011 treatment was associated with improved cardiac function (increased ejection fraction, fraction shortening and preload recruitable stroke work) and myocardial remodeling (reduced left ventricular diameter and volume at both end diastolic and systolic) compared with vehicle treatment. FT011 significantly reduced collagen matrix deposition, myocyte hypertrophy and interstitial macrophage infiltration, and mRNA expression of collagens I and III in NIZ compared with vehicle treatment. Anti-fibrotic therapy with FT011 in MI rats attenuated fibrosis and preserved systolic function.
YihQ is a sulfoquinovosidase that cleaves sulfoquinovosyl diacylglyceride sulfolipids
Publisher: Springer Science and Business Media LLC
Date: 15-02-2016
Abstract: Sulfoquinovose is produced by photosynthetic organisms at a rate of 10(10) tons per annum and is degraded by bacteria as a source of carbon and sulfur. We have identified Escherichia coli YihQ as the first dedicated sulfoquinovosidase and the gateway enzyme to sulfoglycolytic pathways. Structural and mutagenesis studies unveiled the sequence signatures for binding the distinguishing sulfonate residue and revealed that sulfoquinovoside degradation is widespread across the tree of life.
Direct Evidence for ArOS Bond Cleavage upon Inactivation of Pseudomonas aeruginosa Arylsulfatase by Aryl Sulfamates
Publisher: Wiley
Date: 21-02-2008
Abstract: Pseudomonas aeruginosa arylsulfatase catalyses the cleavage of aryl sulfates and is an excellent model for human estrone sulfatase, which is implicated in hormone-dependent breast cancer. Aryl sulfamates are inactivators of sulfatases however, little is known about their mechanism. We studied the inactivation of Pseudomonas aeruginosa arylsulfatase A by a range of aryl sulfamates, including the clinical agent 667COUMATE (STX64) used to inactivate estrone sulfatase. Inactivation was time dependent, irreversible, and active-site directed, consistent with a covalent modification at the active site. In terms of the kinetic parameters of inactivation k(inact) and K(i), K(i) values are in the micromolar to nanomolar range, and the inactivation half-life is less than 30 s. A Brønsted plot of k(inact)/K(i) has a steep slope (beta(lg) = -1.1), which implies that the transition state for the first irreversible chemical step of inactivation involves a high degree of charge transfer and cleavage of the ArO-S bond. Detection of the released phenol and titration of the residual activity showed the stoichiometry of inactivation to be in the range 3-6, with the greatest values found for the most effective inactivators. Thus, multiple sulfamoylation events appear to occur during the inactivation process. These data provide valuable insight into the mechanism of sulfatase inactivation by sulfamates.
Discovery of sulfated metabolites in mycobacteria with a genetic and mass spectrometric approach
Publisher: Proceedings of the National Academy of Sciences
Date: 13-12-2002
Abstract: The study of the metabolome presents numerous challenges, first among them being the cataloging of its constituents. A step in this direction will be the development of tools to identify metabolites that share common structural features. The importance of sulfated molecules in cell–cell communication motivated us to develop a rapid two-step method for identifying these metabolites in microorganisms, particularly in pathogenic mycobacteria. Sulfurcontaining molecules were initially identified by mass spectral analysis of cell extracts from bacteria labeled metabolically with a stable sulfur isotope ( 34 SO \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}_{4}^{2-}\\end{equation*}\\end{document} ). To differentiate sulfated from reduced-sulfur-containing molecules, we employed a mutant lacking the reductive branch of the sulfate assimilation pathway. In these sulfur auxotrophs, heavy sulfate is channeled exclusively into sulfated metabolites. The method was applied to the discovery of several new sulfated molecules in Mycobacterium tuberculosis and Mycobacterium smegmatis . Because a sulfur auxotrophic strain is the only requirement of the approach, many microorganisms can be studied in this manner. Such genetic engineering in combination with stable isotopic labeling can be applied to various metabolic pathways and their products.
A semi-invariant Vα 10+ T cell antigen receptor defines a population of natural killer T cells with distinct glycolipid antigen-recognition properties
Publisher: Springer Science and Business Media LLC
Date: 12-06-2011
DOI: 10.1038/NI.2051
5′-Adenosinephosphosulfate Lies at a Metabolic Branch Point in Mycobacteria
Publisher: Elsevier BV
Date: 09-2002
Structural and mechanistic insight into N-glycan processing by endo-α-mannosidase
Publisher: Proceedings of the National Academy of Sciences
Date: 04-01-2012
Abstract: N-linked glycans play key roles in protein folding, stability, and function. Biosynthetic modification of N-linked glycans, within the endoplasmic reticulum, features sequential trimming and readornment steps. One unusual enzyme, endo-α-mannosidase, cleaves mannoside linkages internally within an N-linked glycan chain, short circuiting the classical N-glycan biosynthetic pathway. Here, using two bacterial orthologs, we present the first structural and mechanistic dissection of endo-α-mannosidase. Structures solved at resolutions 1.7–2.1 Å reveal a ( β / α ) 8 barrel fold in which the catalytic center is present in a long substrate-binding groove, consistent with cleavage within the N-glycan chain. Enzymatic cleavage of authentic Glc 1/3 Man 9 GlcNAc 2 yields Glc 1/3 -Man. Using the bespoke substrate α-Glc-1,3-α-Man fluoride, the enzyme was shown to act with retention of anomeric configuration. Complexes with the established endo-α-mannosidase inhibitor α-Glc-1,3-deoxymannonojirimycin and a newly developed inhibitor, α-Glc-1,3-isofagomine, and with the reducing-end product α-1,2-mannobiose structurally define the -2 to +2 subsites of the enzyme. These structural and mechanistic data provide a foundation upon which to develop new enzyme inhibitors targeting the hijacking of N-glycan synthesis in viral disease and cancer.
Molecular basis of sulfolactate synthesis by sulfolactaldehyde dehydrogenase fromRhizobium leguminosarum
Publisher: Cold Spring Harbor Laboratory
Date: 14-03-2023
DOI: 10.1101/2023.03.13.532361
Abstract: Sulfolactate (SL) is a short-chain organosulfonate that is an important reservoir of sulfur in the biosphere. SL is produced by oxidation of sulfolactaldehyde (SLA), which in turn derives from sulfoglycolysis of the sulfosugar sulfoquinovose, or through oxidation of 2,3-dihydroxypropanesulfonate. Oxidation of SLA is catalyzed by SLA dehydrogenases belonging to the aldehyde dehydrogenase superfamily. We report that SLA dehydrogenase Rl GabD from the sulfoglycolytic bacterium Rhizobium leguminsarum SRDI565 can use both NAD + and NADP + as cofactor to oxidize SLA, and indicatively operates through a rapid equilibrium ordered mechanism. We report the cryo-EM structure of Rl GabD bound to NADH, revealing a tetrameric quaternary structure and supporting proposal of organosulfonate binding residues in the active site, and a catalytic mechanism. Sequence based homology searches identified SLA dehydrogenase homologs in a range of putative sulfoglycolytic gene clusters in bacteria predominantly from the phyla Actinobacteria, Firmicutes, and Proteobacteria. This work provides a structural and biochemical view of SLA dehydrogenases to complement our knowledge of SLA reductases, and provide detailed insights into a critical step in the organosulfur cycle. Sulfolactate is an important species in the biogeochemical sulfur cycle. Herein we report the 3D cryo-EM structure and kinetics of its biosynthetic enzyme, sulfolactaldehyde dehydrogenase.
Corrigendum: Evidence for a Boat Conformation at the Transition State of GH76 α-1,6-Mannanases-Key Enzymes in Bacterial and Fungal Mannoprotein Metabolism
Publisher: Wiley
Date: 02-02-2016
Sulfatase inhibitors: a patent review
Publisher: Informa Healthcare
Date: 08-11-2012
DOI: 10.1517/13543776.2013.736965
Abstract: Steroid sulfatase (STS) converts sulfated hormones to free hormones of importance in hormone-dependent diseases such as breast cancer and endometriosis. Carbohydrate sulfatases degrade complex carbohydrates as part of normal cellular turnover certain lysosomal storage disorders (LSDs) involve defective processing of sulfated glycosaminoglycans by mutant sulfatases. Aryl sulfamates have been developed as STS inhibitors, and STX64 and PGL2001 are under evaluation in Phase I and II clinical trials for treatment of endometrial and metastatic breast and prostate cancers and endometriosis. Dual-acting compounds have emerged that are aromatase inhibitors (AIs), selective estrogen receptor antagonists, or inhibitors of microtubule polymerization. Sulfamidase inhibitors as pharmacological chaperones to assist maturation of folding-defective mutants for the treatment of Sanfilippo type A disease are under investigation. Coverage: The patent literature after the mid-1990s. The failure of STX64 in a Phase II monotherapy clinical trial should not dissuade further investigations in multidrug regimens, particularly in combination with AIs. The recent development of dual-acting compounds may enhance the potential for success in the clinic. Further investigations into aryl sulfamates are required to clarify the molecular mechanism of action additionally, new reversible sulfatase inhibition concepts are needed for the development of pharmacological chaperones for sulfatase LSDs.
5′‐Adenosinephosphosulphate reductase (CysH) protects Mycobacterium tuberculosis against free radicals during chronic infection phase in mice
Publisher: Wiley
Date: 21-02-2006
DOI: 10.1111/J.1365-2958.2006.05075.X
Abstract: A major obstacle to tuberculosis (TB) control is the problem of chronic TB infection (CTBI). Here we report that 5'-adenosinephosphosulphate reductase (CysH), an enzyme essential for the production of reduced-sulphur-containing metabolites, is critical for Mycobacterium tuberculosis (Mtb) survival in chronic infection phase in mice. Disruption of cysH rendered Mtb auxotrophic for cysteine and methionine, and attenuated virulence in BALB/c and C57BL/6 immunocompetent mice. The mutant and wild-type Mtb replicated similarly during the acute phase of infection, but the mutant showed reduced viability during the persistent phase of the infection. The cysH mutant caused disease and death after 4-7 weeks of infection in four different groups of mice - Rag1(-/-), NOS2(-/-), gp91phox(-/-) NOS2(-/-) and gp91phox(-/-) mice given aminoguanidine [to suppress the effects of nitric oxide synthase 2 (NOS2)]- indicating minimal metabolic effect on the cysH mutant survival in these mice. The cysH mutant was also susceptible to peroxynitrite and hydrogen peroxide in vitro. These results show that CysH is important for Mtb protection during the chronic infection phase, and that resistance to nitrosative and oxidative stress may be the mechanism of this protection. Thus, this metabolic gene of an intracellular pathogen could have a secondary role in protection against the host immune response. Finally the lack of an endogenous human orthologue of cysH and its possible role in defence against adaptive immunity renders CysH an attractive enzyme for further studies as a target for therapeutics active against CTBI.
Glycolipids from the gut symbiont Bacteroides fragilis are agonists for natural killer T cells and induce their regulatory differentiation
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3SC02124F
Abstract: Total synthesis of a glycolipid antigen and structural analogues from the human gut commensal Bacteroides fragilis enables demonstration of its antigenic properties and immunoregulatory activity.
Discovery and characterization of a sulfoquinovose mutarotase using kinetic analysis at equilibrium by exchange spectroscopy
Publisher: Portland Press Ltd.
Date: 16-04-2018
DOI: 10.1042/BCJ20170947
Abstract: Bacterial sulfoglycolytic pathways catabolize sulfoquinovose (SQ), or glycosides thereof, to generate a three-carbon metabolite for primary cellular metabolism and a three-carbon sulfonate that is expelled from the cell. Sulfoglycolytic operons encoding an Embden–Meyerhof–Parnas-like or Entner–Doudoroff (ED)-like pathway harbor an uncharacterized gene (yihR in Escherichia coli PpSQ1_00415 in Pseudomonas putida) that is up-regulated in the presence of SQ, has been annotated as an aldose-1-epimerase and which may encode an SQ mutarotase. Our sequence analyses and structural modeling confirmed that these proteins possess mutarotase-like active sites with conserved catalytic residues. We overexpressed the homolog from the sulfo-ED operon of Herbaspirillum seropedicaea (HsSQM) and used it to demonstrate SQ mutarotase activity for the first time. This was accomplished using nuclear magnetic resonance exchange spectroscopy, a method that allows the chemical exchange of magnetization between the two SQ anomers at equilibrium. HsSQM also catalyzed the mutarotation of various aldohexoses with an equatorial 2-hydroxy group, including d-galactose, d-glucose, d-glucose-6-phosphate (Glc-6-P), and d-glucuronic acid, but not d-mannose. HsSQM displayed only 5-fold selectivity in terms of efficiency (kcat/KM) for SQ versus the glycolysis intermediate Glc-6-P however, its proficiency [kuncat/(kcat/KM)] for SQ was 17 000-fold better than for Glc-6-P, revealing that HsSQM preferentially stabilizes the SQ transition state.
Nucleus incertus promotes cortical desynchronization and behavioral arousal.
Publisher: Springer Science and Business Media LLC
Date: 20-05-2016
DOI: 10.1007/S00429-016-1230-0
Abstract: Arousal and vigilance are essential for survival and relevant regulatory neural circuits lie within the brainstem, hypothalamus and forebrain. The nucleus incertus (NI) is a distinct site within the pontine periventricular gray, containing a substantial population of GABAergic neurons with long-range, ascending projections. Existing neuroanatomical data and functional studies in anesthetized rats, suggest the NI is a central component of a midline behavioral control network well positioned to modulate arousal, vigilance and exploratory navigation, yet none of these roles have been established experimentally. We used a chemogenetic approach-clozapine-N-oxide (CNO) activation of virally delivered excitatory hM3Dq-DREADDs-to activate the NI in rats and examined the behavioral and physiological effects, relative to effects in naïve rats and appropriate viral-treated controls. hM3Dq activation by CNO resulted in long-lasting depolarization of NI neurons with action potentials, in vitro. Peripheral injection of CNO significantly increased c-Fos immunoreactivity in the NI and promoted cortical electroencephalograph (EEG) desynchronization. These brain changes were associated with heightened arousal, and increased locomotor activity in the homecage and in a novel environment. Furthermore, NI activation altered responses in a fear conditioning paradigm, reflected by increased head-scanning, vigilant behaviors during conditioned fear recall. These findings provide direct evidence that the NI promotes general arousal via a broad behavioral activation circuit and support early hypotheses, based on its connectivity, that the NI is a modulator of cognition and attention, and emotional and motivated behaviors.
Galactose-derived phosphonate analogues as potential inhibitors of phosphatidylinositol biosynthesis in mycobacteria
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B616450A
Abstract: Galactose-based phosphonate analogues of myo-inositol-1-phosphate and phosphatidylinositol have been synthesized from methyl beta-d-galactopyranoside. Michaelis-Arbuzov reaction of isopropyl diphenyl phosphite or triisopropyl phosphite with a 6-iodo-3,4-isopropylidene galactoside afforded the corresponding phosphonates. Deprotection of the diphenyl phosphonate afforded methyl beta-d-galactoside 6-phosphonate, an analogue of myo-inositol-1-phosphate. The diisopropyl esters of the diisopropyl phosphonate were selectively deprotected and the corresponding anion was coupled with 1,2-dipalmitoyl-sn-glycerol using dicyclohexylcarbodiimide. Deprotection afforded a methyl beta-d-galactoside-derived analogue of phosphatidylinositol. The galactose-derived analogues of phosphatidylinositol and myo-inositol-1-phosphate were not substrates for mycobacterial mannosyltransferases (at concentrations up to 1 mM) involved in phosphatidylinositol mannoside biosynthesis in a cell-free extract of Mycobacterium smegmatis. The galactose-derived phosphonate analogue of phosphatidylinositol was shown to be an inhibitor at 0.01 mM of PimA mannosyltransferase involved in the synthesis of phosphatidylinositol mannoside from phosphatidylinositol, and a weaker inhibitor of the next mannosyltransferase(s), which catalyzes the mannosylation of phosphatidylinositol mannoside.
Glycosyl fluorides in enzymatic reactions
Publisher: Elsevier BV
Date: 07-2000
DOI: 10.1016/S0008-6215(00)00041-0
Abstract: Glycosyl fluorides have considerable importance as substrates and inhibitors in enzymatic reactions. Their good combination of stability and reactivity has enabled their use as glycosyl donors with a variety of carbohydrate processing enzymes. Moreover, the installation of fluorine elsewhere on the carbohydrate scaffold commonly modifies the properties of the glycosyl fluoride such that the resultant compounds act as slow substrates or even inhibitors of enzyme action. This review covers the use of glycosyl fluorides as substrates for wild-type and mutant glycosidases and other enzymes that catalyze glycosyl transfer. The use of substituted glycosyl fluorides as inhibitors of enzymes that catalyze glycosyl transfer and as tools for investigation of their mechanism is discussed, including the labeling of active site residues. Synthetic applications in which glycosyl fluorides are used as glycosyl donors in enzymatic transglycosylation reactions for the synthesis of oligo- and polysaccharides are then covered, including the use of mutant glycosidases, the so-called glycosynthases, which are able to catalyze the formation of glycosides without competing hydrolysis. Finally, a short overview of the use of glycosyl fluorides as substrates and inhibitors of phosphorylases and phosphoglucomutase is given.
A sulfoglycolytic Entner-Doudoroff pathway in Rhizobium leguminosarum bv. trifolii SRDI565
Publisher: Cold Spring Harbor Laboratory
Date: 19-12-2019
DOI: 10.1101/2019.12.17.868638
Abstract: Rhizobia are nitrogen fixing bacteria that engage in symbiotic relationships with plant hosts but can also persist as free-living bacteria with the soil and rhizosphere. Here we show that free living Rhizobium leguminosarum SRDI565 can grow on the sulfosugar sulfoquinovose (SQ) using a sulfoglycolytic Entner-Doudoroff (sulfo-ED) pathway resulting in production of sulfolactate (SL) as the major metabolic end-product. Comparative proteomics supports the involvement of a sulfo-ED operon encoding an ABC transporter cassette, sulfo-ED enzymes and an SL exporter. Consistent with an oligotrophic lifestyle, proteomics data revealed little change in expression of the sulfo-ED proteins during growth on SQ versus mannitol, a result confirmed through biochemical assay of sulfoquinovosidase activity in cell lysates (data are available via ProteomeXchange with identifier PXD015822). Metabolomics analysis showed that growth on SQ involves gluconeogenesis to satisfy metabolic requirements for glucose-6-phosphate and fructose-6-phosphate. Metabolomics analysis also revealed the unexpected production of small amounts of sulfofructose and 2,3-dihydroxypropanesulfonate, which are proposed to arise from promiscuous activities of the glycolytic enzyme phosphoglucose isomerase and a non-specific aldehyde reductase, respectively. This work shows that rhizobial metabolism of the abundant sulfosugar SQ may contribute to persistence of the bacteria in the soil and to mobilization of sulfur in the pedosphere.
Synthesis and Testing of Mechanism‐Based Protein‐Profiling Probes for Retaining Endo‐glycosidases
Publisher: Wiley
Date: 05-01-2006
Abstract: New functional proteomics methods are required for targeting and identification of subsets of a proteome in an activity-based fashion. Glycosidases play critical roles in biology, yet a robust method for functional analysis of their activities and identities in biological proteomes is still lacking. An aryl 2-deoxy-2-fluoro xylobioside inactivator was conjugated through cleavable and noncleavable linker arms to a biotin tag, thereby yielding two new active-site-directed reagents for activity-based profiling of retaining beta-glycanases in complex proteomes. Crucially, these tagged reagents possess high specificity for their target enzymes with kinetic parameters similar to those of the untagged reagent. Western blotting showed that these reagents bind and covalently label active retaining beta-glycanases both in pure enzyme s les and in the secreted proteome of the soil bacterium Cellulomonas fimi. Such reagents therefore show great promise for future activity-based targeting of glycanases.
A patchwork pathway for catabolism of the sulfosugar sulfofucose
Publisher: Cold Spring Harbor Laboratory
Date: 02-08-2023
DOI: 10.1101/2023.08.01.551581
Abstract: We report the isolation of Paracoccus onubensis strain Merri, which can grow on the rare sulfosugar sulfofucose (6-deoxy-6-sulfo-D-galactose) as sole carbon source, leading to its breakdown and release of sulfite. Genome sequencing and comparative proteomics of s les grown on glucose versus sulfofucose identified a genetic locus containing most of the genes for a sulfoglycolytic pathway for breakdown of sulfofucose to the 3-carbon organosulfonate sulfolactaldehyde, and a biomineralization pathway for catabolism of sulfolactaldehyde to pyruvate and sulfite. A candidate sulfotagatose-1-phosphate aldolase was expressed and was active on the epimeric substrate sulfofructose-1-phosphate. Its 3D X-ray structure revealed a close homology to sulfofructose-1-phosphate aldolase from the sulfoglycolytic Embden-Meyerhof-Parnas pathway. A patchwork sulfofucose catabolism pathway is proposed involving a sulfofucolytic Embden-Meyerhof-Parnas and short-chain organosulfonate biomineralization pathway. Sulfosugars are important compounds in the biogeochemical sulfur cycle and are produced by a wide range of photosynthetic plants, algae and cyanobacteria. While the pathways for the biosynthesis and catabolism of sulfoquinovose are well studied, much less is known about the rarer sulfosugar sulfofucose. We report a bacterium that can use sulfofucose as sole carbon source and achieve its complete breakdown to produce sulfite. We propose that sulfofucose catabolism is achieved using enzymes of the sulfoglycolytic Embden-Meyerhof-Parnas pathway that tolerate a change in stereochemistry at C4 of the sulfosugar. The sulfolactaldehyde output of this pathway is broken down to sulfite through a biomineralization pathway via sulfolactate. Microbial metabolism of this rare sulfosugar can be achieved through repurposing enzymes within known sulfosugar and short-chain organosulfonate catabolism catabolism.
Synthesis of the monoterpenoid esters cypellocarpin C and cuniloside B and evidence for their widespread occurrence in Eucalyptus
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.CARRES.2010.07.029
Abstract: Short syntheses of cuniloside B and cypellocarpin C, (+)-(R)-oleuropeic acid-containing carbohydrates, are reported. Also disclosed are syntheses of the noreugenin glycosides, undulatoside A and corymbosins K(1) and K(2). Leaf extracts of 28 erse eucalypts revealed cuniloside B to be present in all, and cypellocarpin C to be present in most, of the species examined. The widespread occurrence of these carbohydrate monoterpenoid esters supports their roles in essential oil biosynthesis or mobilization from sites of synthesis to secretory cavity lumena.
Fleetamine (3-O-α-d-glucopyranosyl-swainsonine): the synthesis of a hypothetical inhibitor of endo-α-mannosidase
Publisher: Elsevier BV
Date: 07-2012
A β-Mannanase with a Lysozyme-like Fold and a Novel Molecular Catalytic Mechanism
Publisher: American Chemical Society (ACS)
Date: 08-11-2016
Genome sequences of Arthrobacter spp. that use a modified sulfoglycolytic Embden-Meyerhof-Parnas pathway
Publisher: Cold Spring Harbor Laboratory
Date: 24-11-2021
DOI: 10.1101/2021.11.24.469816
Abstract: Sulfoglycolysis pathways enable the breakdown of the sulfosugar sulfoquinovose and environmental recycling of its carbon and sulfur content. Several pathways exist for the breakdown of sulfoquinovose that usually lead to production of C3-sulfonates (sulfolactate and 2,3-dihydroxypropanesulfonate) that are excreted and sustain secondary bacterial communities. The prototypical sulfoglycolytic pathway is a variant of the classical Embden-Meyerhof-Parnas pathway that has been described in gram-negative Escherichia coli and results in production of 2,3-dihydroxypropanesulfonate. We used enrichment cultures to discover new sulfoglycolytic bacteria from Australian soil s les. Two gram-positive Arthrobacter spp. were isolated that produced sulfolactate as the metabolic end-product. Genome sequences identified a modified sulfoglycolytic Embden-Meyerhof-Parnas (sulfo-EMP) gene cluster that retained the core sulfoglycolysis genes encoding metabolic enzymes, but featuring the replacement of the gene encoding sulfolactaldehyde (SLA) reductase with SLA dehydrogenase, and the absence of sulfoquinovosidase and sulfoquinovose mutarotase genes. The gene clusters were broadly conserved across a range of other sequenced Actinobacteria. We report the first gram-positive soil bacteria that utilize sulfo-EMP pathways to metabolize SQ. Excretion of sulfolactate is consistent with an aerobic saprophytic lifestyle. This work broadens our knowledge of the sulfo-EMP pathway to include soil bacteria.
Design of Potent Mincle Signalling Agonists Based on an Alkyl b- Glucoside Template
Publisher: American Chemical Society (ACS)
Date: 17-01-2020
DOI: 10.26434/CHEMRXIV.10567097
Abstract: The innate immune receptor Mincle senses lipid-based molecules derived from pathogens, commensals and altered self. Based on emerging structure-activity relationships we design simple alkyl 6- i O /i -acyl-b-D-glucosides that are effective agonists of Mincle and signal with potency on par with the prototypical ligand trehalose dimycolate.
Comprehensive two-dimensional gas chromatography, retention indices and time-of-flight mass spectra of flavonoids and chalcones
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.CHROMA.2010.10.093
Abstract: The applicability of comprehensive two-dimensional gas chromatography (GC×GC) for flavonoids analysis was investigated by separation and identification of flavonoids in standards, and a complex matrix natural s le. The modulation temperature was optimized to achieve the best separation and signal enhancement. The separation pattern of trimethylsilyl (TMS) derivatives of flavonoids was compared on two complementary column sets. Whilst the BPX5/BPX50 (NP/P) column set offers better overall separation, BPX50/BPX5 (P/NP) provides better peak shape and sensitivity. Comparison of the identification power of GC×GC-TOFMS against both the NIST05 MS library and a laboratory (created in-house) TOFMS library was carried out on a flavonoid mixture. The basic retention index information on high-performance capillary columns with a non-polar stationary phase was established and database of mass spectra of trimethylsilyl derivatives of flavonoids was compiled. TOFMS coupled to GC×GC enabled satisfactory identification of flavonoids in complex matrix s les at their LOD over a range of 0.5-10 μg/mL. Detection of all compounds was based on full-scan mass spectra and for each compound a characteristic ion was chosen for further quantification. This study shows that GC×GC-TOFMS yields high specificity for flavonoids derived from real natural s les, dark chocolate, propolis, and chrysanthemum.
An Epoxide Intermediate in Glycosidase Catalysis
Publisher: American Chemical Society (ACS)
Date: 04-09-2019
DOI: 10.26434/CHEMRXIV.9745388.V1
Abstract: Retaining glycoside hydrolases cleave their substrates through stereochemical retention at the anomeric position. Typically, this involves two-step mechanisms using either an enzymatic nucleophile via a covalent glycosyl enzyme intermediate, or neighboring group participation by a substrate-borne 2-acetamido neighboring group via an oxazoline intermediate no enzymatic mechanism with participation of the sugar 2-hydroxyl has been reported. Here, we detail structural, computational and kinetic evidence for neighboring group participation by a mannose 2-hydroxyl in glycoside hydrolase family 99 endo-α-1,2-mannanases. We present a series of crystallographic snapshots of key species along the reaction coordinate: a Michaelis complex with a tetrasaccharide substrate complexes with intermediate mimics, β-1,2-aziridine and β-1,2-epoxide and a product complex. The 1,2-epoxide intermediate mimic displayed hydrolytic and transfer reactivity analogous to that expected for the 1,2-anhydro sugar intermediate supporting its catalytic equivalence. Quantum mechanics/molecular mechanics modelling of the reaction coordinate predicted a reaction pathway through a 1,2-anhydro sugar via a transition state in an unprecedented flattened, envelope ( E 3 ) conformation. Kinetic isotope effects for anomeric- 2 H and anomeric- 13 C support an oxocarbenium ion-like transition state and that for C2- 18 O (1.052 ± 0.006) directly implicates nucleophilic participation by the C2-hydroxyl. Collectively, these data substantiate this unprecedented and long-imagined enzymatic mechanism.
Antigen specificity of type i NKT cells is governed by TCR β-chain diversity
Publisher: The American Association of Immunologists
Date: 15-11-2015
Abstract: NKT cells recognize lipid-based Ags presented by CD1d. Type I NKT cells are often referred to as invariant owing to their mostly invariant TCR α-chain usage (Vα14-Jα18 in mice, Vα24-Jα18 in humans). However, these cells have erse TCR β-chains, including Vβ8, Vβ7, and Vβ2 in mice and Vβ11 in humans, joined to a range of TCR Dβ and Jβ genes. In this study, we demonstrate that TCR β-chain composition can dramatically influence lipid Ag recognition in an Ag-dependent manner. Namely, the glycolipids α-glucosylceramide and isoglobotrihexosylceramide were preferentially recognized by Vβ7+ NKT cells from mice, whereas the α-galactosylceramide analog OCH, with a truncated sphingosine chain, was preferentially recognized by Vβ8+ NKT cells from mice. We show that the influence of the TCR β-chain is due to a combination of Vβ-, Jβ-, and CDR3β-encoded residues and that these TCRs can recapitulate the selective Ag reactivity in TCR-transduced cell lines. Similar observations were made with human NKT cells where different CDR3β-encoded residues determined Ag preference. These findings indicate that NKT TCR β-chain ersity results in differential and nonhierarchical Ag recognition by these cells, which implies that some Ags can preferentially activate type I NKT cell subsets.
Novel microsomal triglyceride transfer protein inhibitors
Publisher: Informa Healthcare
Date: 04-2003
Concise synthesis of sulfoquinovose and sulfoquinovosyl diacylglycerides, and development of a fluorogenic substrate for sulfoquinovosidases
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9OB02540E
Abstract: A new and efficient synthesis of sulfoquinovose [including ( 13 C 6 )-SQ] and of saturated and unsaturated sulfoquinovosyl diacylglycerol derivatives, and development of a fluorogenic glycoside useful for kinetic investigations on sulfoquinovosidases.
Synthesis and structure of clozapine N-oxide hemi(hydrochloride): an infinite hydrogen-bonded poly[n]catenane
Publisher: International Union of Crystallography (IUCr)
Date: 27-09-2022
DOI: 10.1107/S2056989022009306
Abstract: The structure of the title compound, 2C 18 H 19 ClN 4 O·HCl or (CNO) 2 ·HCl (C 36 H 39 Cl 3 N 8 O 2 ), at 100 K has tetragonal ( I 4/ m ) symmetry. The dihedral angle between the benzene rings of the fused ring system of the CNO molecule is 40.08 (6)° and the equivalent angle between the seven-membered ring and its pendant N -oxide ring is 31.14 (7)°. The structure contains a very strong, symmetrical O—H...O hydrogen bond [O...O = 2.434 (2) Å] between two equivalent R 3 N + —O − moieties, which share a proton lying on a crystallographic twofold rotation axis. These units then form a (CNO) 4 ·(HCl) 2 ring by way of two equivalent N—H...Cl hydrogen bonds (Cl − site symmetry m ). These rings are catenated into infinite chains propagating along the c -axis direction by way of shape complementarity and directional C—H...N and C—H...π interactions.
Letter to the glycoforum transforming glycoscience: An Australian perspective
Publisher: Oxford University Press (OUP)
Date: 06-12-2014
Candida albicans steryl 6-O-acyl-α-d -mannosides agonize signalling through Mincle
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CC06263D
Abstract: Cholesteryl and ergosteryl 6- O -acyl-α- d -mannosides from Candida albicans signal through the innate immunity receptor Mincle.
An Epoxide Intermediate in Glycosidase Catalysis
Publisher: American Chemical Society (ACS)
Date: 04-09-2019
DOI: 10.26434/CHEMRXIV.9745388
Abstract: Retaining glycoside hydrolases cleave their substrates through stereochemical retention at the anomeric position. Typically, this involves two-step mechanisms using either an enzymatic nucleophile via a covalent glycosyl enzyme intermediate, or neighboring group participation by a substrate-borne 2-acetamido neighboring group via an oxazoline intermediate no enzymatic mechanism with participation of the sugar 2-hydroxyl has been reported. Here, we detail structural, computational and kinetic evidence for neighboring group participation by a mannose 2-hydroxyl in glycoside hydrolase family 99 endo-α-1,2-mannanases. We present a series of crystallographic snapshots of key species along the reaction coordinate: a Michaelis complex with a tetrasaccharide substrate complexes with intermediate mimics, β-1,2-aziridine and β-1,2-epoxide and a product complex. The 1,2-epoxide intermediate mimic displayed hydrolytic and transfer reactivity analogous to that expected for the 1,2-anhydro sugar intermediate supporting its catalytic equivalence. Quantum mechanics/molecular mechanics modelling of the reaction coordinate predicted a reaction pathway through a 1,2-anhydro sugar via a transition state in an unprecedented flattened, envelope ( i E /i sub /sub ) conformation. Kinetic isotope effects for anomeric- sup /sup H and anomeric- sup /sup C support an oxocarbenium ion-like transition state and that for C2- sup /sup O (1.052 ± 0.006) directly implicates nucleophilic participation by the C2-hydroxyl. Collectively, these data substantiate this unprecedented and long-imagined enzymatic mechanism. / br /
C2-Oxyanion Neighboring Group Participation: Transition State Structure for the Hydroxide-Promoted Hydrolysis of 4-Nitrophenyl α-d-Mannopyranoside
Publisher: American Chemical Society (ACS)
Date: 18-10-2016
DOI: 10.1021/JACS.6B07935
Abstract: The hydroxide-catalyzed hydrolysis of aryl 1,2-trans-glycosides proceeds through a mechanism involving neighboring group participation by a C2-oxyanion and rate-limiting formation of a 1,2-anhydro sugar (oxirane) intermediate. The transition state for the hydroxide-catalyzed hydrolysis of 4-nitrophenyl α-d-mannopyranoside in aqueous media has been studied by the use of multiple kinetic isotope effect (KIE) measurements in conjunction with ab initio theoretical methods. The experimental KIEs are C1-
Structural and Biochemical Insights into the Function and Evolution of Sulfoquinovosidases
Publisher: American Chemical Society (ACS)
Date: 05-09-2018
Cardioprotective 3',4'-dihydroxyflavonol attenuation of JNK and p38 MAPK signalling involves CaMKII inhibition
Publisher: Portland Press Ltd.
Date: 08-11-2013
DOI: 10.1042/BJ20121538
Abstract: DiOHF (3′,4′-dihydroxyflavonol) is cardioprotective against I/R (ischaemia/reperfusion) injury. The biological activities of flavonols are associated with kinase modulation to alter cell signalling. We thus investigated the effects of DiOHF on the activation of MAPKs (mitogen-activated protein kinases) that regulate the cardiac stress response. In an ovine model of I/R, JNK (c-Jun N-terminal kinase), p38MAPK, ERK (extracellular-signal-regulated kinase) and Akt were activated, and NP202, a pro-drug of DiOHF, reduced infarct size and inhibited JNK and p38MAPK activation, whereas ERK and Akt phosphorylation were unaltered. Similarly, in cultured myoblasts, DiOHF pre-treatment preserved viability and inhibited activation of JNK and p38MAPK, but not ERK in response to acute oxidative and chemotoxic stress. Furthermore, DiOHF prevented stress-activation of the direct upstream regulators MKK4/7 (MAPK kinase 4/7) and MKK3/6 respectively. We utilized small-molecule affinity purification and identified CaMKII (Ca2+/calmodulin-dependent protein kinase II) as a kinase targeted by DiOHF and demonstrated potent CaMKII inhibition by DiOHF in vitro. Moreover, the specific inhibition of CaMKII with KN-93, but not KN-92, prevented oxidative stress-induced activation of JNK and p38MAPK. The present study indicates DiOHF inhibition of CaMKII and attenuation of MKK3/6→p38MAPK and MKK4/7→JNK signalling as a requirement for the protective effects of DiOHF against stress stimuli and myocardial I/R injury.
Synthesis of Sulfated Glucosaminides for Profiling Substrate Specificities of Sulfatases and Fungal β‐N‐Acetylhexosaminidases
Publisher: Wiley
Date: 06-02-2009
Abstract: Systematic sulfation: Sulfated glycoconjugates are degraded either by desulfation followed by glycoside cleavage, or by glycoside cleavage followed by desulfation. To study these processes, here we report the synthesis of four regioisomerically sulfated p-nitrophenyl glucosaminides from the common precursor p-nitrophenyl N-acetyl-beta-D-glucosaminide. These substrates allowed the rapid analysis of the substrate preferences of a set of four sulfatases and 24 hexosaminidases.Sulfated carbohydrates are components of many glycoconjugates, and are degraded by two major processes: cleavage of the sulfate ester by a sulfatase, or en bloc removal of a sulfated monosaccharide by a glycoside hydrolase. However, these processes have proved difficult to study owing to a lack of homogeneous, defined substrates. We describe here the synthesis of a series of p-nitrophenyl beta-D-glucosaminides bearing sulfate esters at the 2-, 3-, 4- or 6-positions, by ergent routes starting with p-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside. The sulfated p-nitrophenyl beta-D-glucosaminides were used to study the substrate specificity of four sulfatases (from Helix pomatia, Patella vulgata, abalone, and Pseudomonas aeruginosa), and revealed significant differences in the preference of each of these enzymes for desulfation at different positions around the sugar ring. The 3-, 4- and 6-sulfated p-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucosaminides were screened against a panel of 24 fungal beta-N-acetylhexosaminidases to assess their substrate specificity. While the 4- and 6-sulfates were substrates for many of the fungal enzymes investigated, only a single beta-N-acetylhexosaminidase, that from Penicillium chrysogenum, could hydrolyze the 3-sulfated p-nitrophenyl glycoside. Together these results demonstrate the utility of sulfated p-nitrophenyl beta-D-glucosaminides for the study of both sulfatases and glycoside hydrolases.
Related Organisations
University Of California, Berkeley
Location: United States of America
Related Funding Activities
Discovery Projects - Grant ID: DP180101957
Start Date: 07-2018
End Date: 06-2021
Amount: $496,925.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0560742
Start Date: 2005
End Date: 12-2008
Amount: $72,444.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP120101396
Start Date: 04-2012
End Date: 03-2015
Amount: $360,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0770839
Start Date: 2008
End Date: 12-2010
Amount: $250,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP210100233
Start Date: 07-2021
End Date: 06-2025
Amount: $590,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0449626
Start Date: 01-2004
End Date: 12-2007
Amount: $315,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP210100235
Start Date: 06-2021
End Date: 05-2024
Amount: $445,000.00
Funder: Australian Research Council
View Funded ActivityARC Future Fellowships - Grant ID: FT130100103
Start Date: 02-2014
End Date: 12-2017
Amount: $872,240.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP160100597
Start Date: 2016
End Date: 12-2019
Amount: $631,626.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0877716
Start Date: 01-2008
End Date: 12-2011
Amount: $255,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE210100083
Start Date: 04-2021
End Date: 09-2022
Amount: $777,493.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE0775481
Start Date: 2007
End Date: 12-2007
Amount: $304,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE100100109
Start Date: 10-2010
End Date: 12-2010
Amount: $530,000.00
Funder: Australian Research Council
View Funded ActivityIndustrial Transformation Training Centres - Grant ID: IC170100020
Start Date: 07-2018
End Date: 12-2024
Amount: $3,279,502.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0449625
Start Date: 12-2003
End Date: 12-2007
Amount: $390,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP130102763
Start Date: 2013
End Date: 06-2016
Amount: $360,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE0989125
Start Date: 2009
End Date: 12-2010
Amount: $150,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP1093356
Start Date: 04-2010
End Date: 06-2013
Amount: $330,000.00
Funder: Australian Research Council
View Funded Activity