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Bahadori S, Archambault MJ, Sebastiao M, Bourgault S, Giguère D. Convergent Synthesis of a Group B Streptococcus Type III Epitope Toward a Semisynthetic Carbohydrate-Based Vaccine. J Org Chem 2024. [PMID: 39033407 DOI: 10.1021/acs.joc.4c01216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
In this work, we synthesized an hexasaccharide derived from the capsular polysaccharide of group B Streptococcus type III capsular polysaccharide. Our convergent 3 + 3 strategy avoided the use of benzyl protecting groups allowing the installation of an azide anchoring group and providing a high yield for the final deprotection steps. Moreover, the minimal hexasaccharidic epitope was conjugated to CRM197 and BSA via copper-catalyzed azide-alkyne cycloaddition for the preparation of a semisynthetic carbohydrate-based vaccine.
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Affiliation(s)
- Sam Bahadori
- Département de Chimie, Université Laval, 1045 Av. de la Médecine, Québec City, Quebec G1V 0A6, Canada
- Quebec Network for Research on Protein Function, Engineering and Applications, PROTEO, Montreal, Quebec H2X 3Y7, Canada
| | - Marie-Jeanne Archambault
- Quebec Network for Research on Protein Function, Engineering and Applications, PROTEO, Montreal, Quebec H2X 3Y7, Canada
- Department of Chemistry, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada
| | - Mathew Sebastiao
- Quebec Network for Research on Protein Function, Engineering and Applications, PROTEO, Montreal, Quebec H2X 3Y7, Canada
- Department of Chemistry, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada
| | - Steve Bourgault
- Quebec Network for Research on Protein Function, Engineering and Applications, PROTEO, Montreal, Quebec H2X 3Y7, Canada
- Department of Chemistry, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada
| | - Denis Giguère
- Département de Chimie, Université Laval, 1045 Av. de la Médecine, Québec City, Quebec G1V 0A6, Canada
- Quebec Network for Research on Protein Function, Engineering and Applications, PROTEO, Montreal, Quebec H2X 3Y7, Canada
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2
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Nejatie A, Akintola O, Steves E, Shamsi Kazem Abadi S, Moore MM, Bennet AJ. Structurally homologous sialidases exhibit a commonality in reactivity: Glycoside hydrolase-catalyzed hydrolysis of Kdn-thioglycosides. Bioorg Chem 2020; 106:104484. [PMID: 33268005 DOI: 10.1016/j.bioorg.2020.104484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 10/19/2020] [Accepted: 11/16/2020] [Indexed: 10/23/2022]
Abstract
Aspergillus fumigatus is one of the main causative agents of invasive aspergillosis, an often-lethal fungal disease that affects immunocompromised individuals. A. fumigatus produces a sialidase that cleaves the nine-carbon carbohydrate Kdn from glycoconjugates. This enzyme plays a critical role in A. fumigatus pathogenicity, and is thus a target for the development of new therapeutics. In order to understand the reactivity of this Kdnase, and to develop a sensitive and selective assay for its catalytic activity we determined whether, like its close structural homolog the excreted sialidase produced by Micromonospora viridifaciens, this enzyme can efficiently hydrolyze thioglycoside substrates. We synthesized a panel of seven aryl 2-thio-d-glycero-α-d-galacto-non-2-ulopyranosonides and measured the activity of the A. fumigatus Kdnase towards these substrates. Four of these substrates were hydrolyzed by the A. fumigatus enzyme, although M. viridifaciens sialidase-catalyzed the hydrolysis of these Kdn thioglycosides with higher catalytic efficiencies (kcat/Km). We also tested an enzyme that was evolved from MvNA to improve its activity against Kdn glycosides (Glycobiology 2020, 30, 325). All three enzymes catalyzed the hydrolysis of the four most reactive Kdn thioglycosides and their second-order rate constants (kcat/Km) display a concave downwards Brønsted plot. The kinetic data, for each enzyme, is consistent with a change in rate-limiting step from CS bond cleavage for thioglycosides in which the pKa of the corresponding aryl thiol is >3.6, to a non-chemical step, which is likely a conformational change, that occurs prior to CS bond cleavage for the 2,3,4,5,6-pentafluorothiophenyl glycoside.
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Affiliation(s)
- Ali Nejatie
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Oluwafemi Akintola
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Elizabeth Steves
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Saeideh Shamsi Kazem Abadi
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Margo M Moore
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada
| | - Andrew J Bennet
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby V5A 1S6, Canada.
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3
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Shamsi Kazem Abadi S, Deen MC, Watson JN, Shidmoossavee FS, Bennet AJ. Directed evolution of a remarkably efficient Kdnase from a bacterial neuraminidase. Glycobiology 2019; 30:325-333. [DOI: 10.1093/glycob/cwz099] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 11/19/2019] [Accepted: 11/19/2019] [Indexed: 11/12/2022] Open
Abstract
AbstractN-acetylneuraminic acid (5-acetamido-3,5-dideoxy-d-glycero-d-galacto-non-2-ulosonic acid), which is the principal sialic acid family member of the non-2-ulosonic acids and their various derivatives, is often found at the terminal position on the glycan chains that adorn all vertebrate cells. This terminal position combined with subtle variations in structure and linkage to the underlying glycan chains between humans and other mammals points to the importance of this diverse group of nine-carbon sugars as indicators of the unique aspects of human evolution and is relevant to understanding an array of human conditions. Enzymes that catalyze the removal N-acetylneuraminic acid from glycoconjugates are called neuraminidases. However, despite their documented role in numerous diseases, due to the promiscuous activity of many neuraminidases, our knowledge of the functions and metabolism of many sialic acids and the effect of the attachment to cellular glycans is limited. To this end, through a concerted effort of generation of random and site-directed mutagenesis libraries, subsequent screens and positive and negative evolutionary selection protocols, we succeeded in identifying three enzyme variants of the neuraminidase from the soil bacterium Micromonospora viridifaciens with markedly altered specificity for the hydrolysis of natural Kdn (3-deoxy-d-glycero-d-galacto-non-2-ulosonic acid) glycosidic linkages compared to those of N-acetylneuraminic acid. These variants catalyze the hydrolysis of Kdn-containing disaccharides with catalytic efficiencies (second-order rate constants: kcat/Km) of greater than 105 M−1 s−1; the best variant displayed an efficiency of >106 M−1 s−1 at its optimal pH.
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Affiliation(s)
- Saeideh Shamsi Kazem Abadi
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Matthew C Deen
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Jacqueline N Watson
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Fahimeh S Shidmoossavee
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Andrew J Bennet
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
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4
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Hydrolysis of Glycosyl Thioimidates by Glycoside Hydrolase Requires Remote Activation for Efficient Activity. Catalysts 2019. [DOI: 10.3390/catal9100826] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Chemoenzymatic synthesis of glycosides relies on efficient glycosyl donor substrates able to react rapidly and efficiently, yet with increased stability towards chemical or enzymatic hydrolysis. In this context, glycosyl thioimidates have previously been used as efficient donors, in the case of hydrolysis or thioglycoligation. In both cases, the release of the thioimidoyl aglycone was remotely activated through a protonation driven by a carboxylic residue in the active site of the corresponding enzymes. A recombinant glucosidase (DtGly) from Dictyoglomus themophilum, previously used in biocatalysis, was also able to use such glycosyl thioimidates as substrates. Yet, enzymatic kinetic values analysis, coupled to mutagenesis and in silico modelling of DtGly/substrate complexes demonstrated that the release of the thioimidoyl moiety during catalysis is only driven by its leaving group ability, without the activation of a remote protonation. In the search of efficient glycosyl donors, glycosyl thioimidates are attractive and efficient. Their utility, however, is limited to enzymes able to promote leaving group release by remote activation.
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Nasseri SA, Betschart L, Opaleva D, Rahfeld P, Withers SG. A Mechanism-Based Approach to Screening Metagenomic Libraries for Discovery of Unconventional Glycosidases. Angew Chem Int Ed Engl 2018; 57:11359-11364. [PMID: 30001477 DOI: 10.1002/anie.201806792] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 07/10/2018] [Indexed: 11/11/2022]
Abstract
Functional metagenomics has opened new opportunities for enzyme discovery. To exploit the full potential of this new tool, the design of selective screens is essential, especially when searching for rare enzymes. To identify novel glycosidases that employ cleavage strategies other than the conventional Koshland mechanisms, a suitable screen was needed. Focusing on the unsaturated glucuronidases (UGLs), it was found that use of simple aryl glycoside substrates did not allow sufficient discrimination against β-glucuronidases, which are widespread in bacteria. While conventional glycosidases cannot generally hydrolyze thioglycosides efficiently, UGLs follow a distinct mechanism that allows them to do so. Thus, fluorogenic thioglycoside substrates featuring thiol-based self-immolative linkers were synthesized and assessed as selective substrates. The generality of the approach was validated with another family of unconventional glycosidases, the GH4 enzymes. Finally, the utility of these substrates was tested by screening a small metagenomic library.
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Affiliation(s)
- Seyed Amirhossein Nasseri
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Leo Betschart
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Daria Opaleva
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Peter Rahfeld
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
| | - Stephen G Withers
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada
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6
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Nasseri SA, Betschart L, Opaleva D, Rahfeld P, Withers SG. A Mechanism-Based Approach to Screening Metagenomic Libraries for Discovery of Unconventional Glycosidases. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201806792] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | - Leo Betschart
- Department of Chemistry; University of British Columbia; Vancouver British Columbia V6T 1Z1 Canada
| | - Daria Opaleva
- Department of Chemistry; University of British Columbia; Vancouver British Columbia V6T 1Z1 Canada
| | - Peter Rahfeld
- Department of Chemistry; University of British Columbia; Vancouver British Columbia V6T 1Z1 Canada
| | - Stephen G. Withers
- Department of Chemistry; University of British Columbia; Vancouver British Columbia V6T 1Z1 Canada
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7
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Khazaei K, Yeung JH, Moore MM, Bennet AJ. Inhibitory efficiencies for mechanism-based inactivators of sialidases. CAN J CHEM 2015. [DOI: 10.1139/cjc-2015-0245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Here we describe the measurement of the inactivation rate constants for the mechanism-based inactivator 2,3-difluorosialic acid acting upon the sialidase from Micromonospora viridifaciens. Using double mixing stopped-flow experiments conducted in a 3-(N-morpholino)propanesulfonic acid buffer (100 mmol/L, pH 7.00) at 25 °C, the derived kinetic parameters are kinact/Ki = (3.9 ± 0.8) × 106 (mol/L)–1 s–1 and Ki = 1.7 ± 0.4 μmol/L. We demonstrate that the inhibitory efficiency of the inactivation event is similar to the catalytic efficiency for this sialidase acting upon a typical substrate, 4-methylumbelliferone α-d-sialoside, kcat/Km = (7.2 ± 2.8) × 106 (mol/L)–1 s–1. Furthermore, we show that the catalytic efficiencies for inactivation and hydrolysis by the Kdnase from Aspergillus fumigatus are similar for the corresponding Kdn-analogues. We conclude that the deactivating effect of incorporating an axial 3-fluoro substituent onto the sialic acid scaffold is comparable to the enhanced activation that occurs when the 4-methylumbelliferone leaving group is changed to the more nucleofugal fluoride ion.
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Affiliation(s)
- Kobra Khazaei
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Juliana H.F. Yeung
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Margo M. Moore
- Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
| | - Andrew J. Bennet
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada
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8
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Cheng LL, Shidmoossavee FS, Bennet AJ. Neuraminidase Substrate Promiscuity Permits a Mutant Micromonospora viridifaciens Enzyme To Synthesize Artificial Carbohydrates. Biochemistry 2014; 53:3982-89. [DOI: 10.1021/bi500203p] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Lydia L. Cheng
- Departments
of Chemistry
and Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Fahimeh S. Shidmoossavee
- Departments
of Chemistry
and Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Andrew J. Bennet
- Departments
of Chemistry
and Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
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9
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Chan J, Watson JN, Lu A, Cerda VC, Borgford TJ, Bennet AJ. Bacterial and Viral Sialidases: Contribution of the Conserved Active Site Glutamate to Catalysis. Biochemistry 2011; 51:433-41. [DOI: 10.1021/bi201019n] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jefferson Chan
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British
Columbia V5A 1S6, Canada
| | - Jacqueline N. Watson
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British
Columbia V5A 1S6, Canada
| | - April Lu
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British
Columbia V5A 1S6, Canada
| | - Viviana C. Cerda
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British
Columbia V5A 1S6, Canada
| | - Thor J. Borgford
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British
Columbia V5A 1S6, Canada
| | - Andrew J. Bennet
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British
Columbia V5A 1S6, Canada
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10
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Chan J, Lu A, Bennet AJ. Turnover Is Rate-Limited by Deglycosylation for Micromonospora viridifaciens Sialidase-Catalyzed Hydrolyses: Conformational Implications for the Michaelis Complex. J Am Chem Soc 2011; 133:2989-97. [DOI: 10.1021/ja109199p] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jefferson Chan
- Departments of Chemistry and Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - April Lu
- Departments of Chemistry and Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
| | - Andrew J. Bennet
- Departments of Chemistry and Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
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11
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Chan J, Sandhu G, Bennet AJ. A mechanistic study of sialic acid mutarotation: Implications for mutarotase enzymes. Org Biomol Chem 2011; 9:4818-22. [DOI: 10.1039/c1ob05079f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Carapito R, Imberty A, Jeltsch JM, Byrns SC, Tam PH, Lowary TL, Varrot A, Phalip V. Molecular basis of arabinobio-hydrolase activity in phytopathogenic fungi: crystal structure and catalytic mechanism of Fusarium graminearum GH93 exo-alpha-L-arabinanase. J Biol Chem 2009; 284:12285-96. [PMID: 19269961 PMCID: PMC2673297 DOI: 10.1074/jbc.m900439200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Revised: 02/19/2009] [Indexed: 11/06/2022] Open
Abstract
The phytopathogenic fungus Fusarium graminearum secretes a very diverse pool of glycoside hydrolases (GHs) aimed at degrading plant cell walls. alpha-l-Arabinanases are essential GHs participating in the complete hydrolysis of hemicellulose, a natural resource for various industrial processes, such as bioethanol or pharmaceuticals production. Arb93A, the exo-1,5-alpha-l-arabinanase of F. graminearum encoded by the gene fg03054.1, belongs to the GH93 family, for which no structural data exists. The enzyme is highly active (1065 units/mg) and displays a strict substrate specificity for linear alpha-1,5-l-arabinan. Biochemical assays and NMR experiments demonstrated that the enzyme releases alpha-1,5-l-arabinobiose from the nonreducing end of the polysaccharide. We determined the crystal structure of the native enzyme and its complex with alpha-1,5-l-arabinobiose, a degradation product of alpha-Me-1,5-l-arabinotetraose, at 1.85 and 2.05A resolution, respectively. Arb93A is a monomeric enzyme, which presents the six-bladed beta-propeller fold characteristic of sialidases of clan GHE. The configuration of the bound arabinobiose is consistent with the retaining mechanism proposed for the GH93 family. Catalytic residues were proposed from the structural analysis, and site-directed mutagenesis was used to validate their role. They are significantly different from those observed for GHE sialidases.
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Affiliation(s)
- Raphaël Carapito
- UMR 7175, Ecole Supérieure de Biotechnologie de Strasbourg, Université de Strasbourg-CNRS, Boulevard Sébastien Brandt, BP 10413, 67412 Illkirch-Graffenstaden, France
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13
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Shen H, Byers LD. Thioglycoside hydrolysis catalyzed by β-glucosidase. Biochem Biophys Res Commun 2007; 362:717-20. [PMID: 17727815 DOI: 10.1016/j.bbrc.2007.08.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Accepted: 08/09/2007] [Indexed: 11/20/2022]
Abstract
Sweet almond beta-glucosidase (EC 3.2.1.21) has been shown to have significant thioglycohydrolase activity. While the Km values for the S- and O-glycosides are similar, the k(cat) values are about 1000-times lower for the S-glycosides. Remarkably, the pH-profile for k(cat)/Km for hydrolysis of p-nitrophenyl thioglucoside (pNPSG) shows the identical dependence on a deprotonated carboxylate (pKa 4.5) and a protonated group (pKa 6.7) as does the pH-profile for hydrolysis of the corresponding O-glycoside. Not surprisingly, in spite of the requirement for the presence of this protonated group in catalytically active beta-glucosidase, thioglucoside hydrolysis does not involve general acid catalysis. There is no solvent kinetic isotope effect on the enzyme-catalyzed hydrolysis of pNPSG.
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Affiliation(s)
- Hong Shen
- Department of Chemistry, Tulane University, New Orleans, LA 70118, USA
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14
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Indurugalla D, Watson JN, Bennet AJ. Natural sialoside analogues for the determination of enzymatic rate constants. Org Biomol Chem 2006; 4:4453-9. [PMID: 17268638 DOI: 10.1039/b613909d] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two isomeric 4-methylumbelliferyl-alpha-D-N-acetylneuraminylgalactopyranosides (1 and 2) were synthesised. These compounds contain either the natural alpha-2,3 or alpha-2,6 sialyl-galactosyl linkages, as well as an attached 4-methylumbelliferone for convenient detection of their hydrolyses. These compounds were designed as natural sialoside analogues to be used in a continuous assay of sialidase activity, where the sialidase-catalysed reaction is coupled with an exo-beta-galactosidase-catalysed hydrolysis of the released galactoside to give free 4-methylumbelliferone. The kinetic parameters for 1 and 2 were measured using the wild-type and nucleophilic mutant Y370G recombinant sialidase from Micromonospora viridifaciens. Kinetic parameters for these analogues measured using the new continuous assay were in good agreement with the parameters for the natural substrate, 3'-sialyl lactose. Given the selection of commercially available exo-beta-galactosidases that possess a variety of pH optima, this new method was used to characterise the full pH profile of the wild-type sialidase with the natural sialoside analogue 1. Thus, use of these new substrates 1 and 2 in a continuous assay mode, which can be detected by UV/Vis or fluorescence spectroscopy, makes characterisation of sialidase activity with natural sialoside linkages much more facile.
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Affiliation(s)
- Deepani Indurugalla
- Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6
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