1
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Doyle L, Ovchinnikova OG, Huang BS, Forrester TJB, Lowary TL, Kimber MS, Whitfield C. Mechanism and linkage specificities of the dual retaining β-Kdo glycosyltransferase modules of KpsC from bacterial capsule biosynthesis. J Biol Chem 2023; 299:104609. [PMID: 36924942 PMCID: PMC10148158 DOI: 10.1016/j.jbc.2023.104609] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/09/2023] [Accepted: 03/10/2023] [Indexed: 03/15/2023] Open
Abstract
KpsC is a dual-module glycosyltransferase (GT) essential for "group 2" capsular polysaccharide biosynthesis in Escherichia coli and other Gram-negative pathogens. Capsules are vital virulence determinants in high-profile pathogens, making KpsC a viable target for intervention with small-molecule therapeutic inhibitors. Inhibitor development can be facilitated by understanding the mechanism of the target enzyme. Two separate GT modules in KpsC transfer 3-deoxy-β-d-manno-oct-2-ulosonic acid (β-Kdo) from cytidine-5'-monophospho-β-Kdo donor to a glycolipid acceptor. The N-terminal and C-terminal modules add alternating Kdo residues with β-(2→4) and β-(2→7) linkages, respectively, generating a conserved oligosaccharide core that is further glycosylated to produce diverse capsule structures. KpsC is a retaining GT, which retains the donor anomeric carbon stereochemistry. Retaining GTs typically use an SNi (substitution nucleophilic internal return) mechanism, but recent studies with WbbB, a retaining β-Kdo GT distantly related to KpsC, strongly suggest that this enzyme uses an alternative double-displacement mechanism. Based on the formation of covalent adducts with Kdo identified here by mass spectrometry and X-ray crystallography, we determined that catalytically important active site residues are conserved in WbbB and KpsC, suggesting a shared double-displacement mechanism. Additional crystal structures and biochemical experiments revealed the acceptor binding mode of the β-(2→4)-Kdo transferase module and demonstrated that acceptor recognition (and therefore linkage specificity) is conferred solely by the N-terminal α/β domain of each GT module. Finally, an Alphafold model provided insight into organization of the modules and a C-terminal membrane-anchoring region. Altogether, we identified key structural and mechanistic elements providing a foundation for targeting KpsC.
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Affiliation(s)
- Liam Doyle
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Olga G Ovchinnikova
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Bo-Shun Huang
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
| | - Taylor J B Forrester
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Todd L Lowary
- Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada; Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
| | - Matthew S Kimber
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
| | - Chris Whitfield
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
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2
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Forrester TJB, Ovchinnikova OG, Li Z, Kitova EN, Nothof JT, Koizumi A, Klassen JS, Lowary TL, Whitfield C, Kimber MS. The retaining β-Kdo glycosyltransferase WbbB uses a double-displacement mechanism with an intermediate adduct rearrangement step. Nat Commun 2022; 13:6277. [PMID: 36271007 PMCID: PMC9587256 DOI: 10.1038/s41467-022-33988-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 10/07/2022] [Indexed: 12/25/2022] Open
Abstract
WbbB, a lipopolysaccharide O-antigen synthesis enzyme from Raoultella terrigena, contains an N-terminal glycosyltransferase domain with a highly modified architecture that adds a terminal β-Kdo (3-deoxy-D-manno-oct-2-ulosonic acid) residue to the O-antigen saccharide, with retention of stereochemistry. We show, using mass spectrometry, that WbbB forms a covalent adduct between the catalytic nucleophile, Asp232, and Kdo. We also determine X-ray structures for the CMP-β-Kdo donor complex, for Kdo-adducts with D232N and D232C WbbB variants, for a synthetic disaccharide acceptor complex, and for a ternary complex with both a Kdo-adduct and the acceptor. Together, these structures show that the enzyme-linked Asp232-Kdo adduct rotates to reposition the Kdo into a second sub-site, which then transfers Kdo to the acceptor. Retaining glycosyltransferases were thought to use only the front-side SNi substitution mechanism; here we show that retaining glycosyltransferases can also potentially use double-displacement mechanisms, but incorporating an additional catalytic subsite requires rearrangement of the protein's architecture.
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Affiliation(s)
- Taylor J. B. Forrester
- grid.34429.380000 0004 1936 8198Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road E., Guelph, ON N1G 2W1 Canada
| | - Olga G. Ovchinnikova
- grid.34429.380000 0004 1936 8198Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road E., Guelph, ON N1G 2W1 Canada
| | - Zhixiong Li
- grid.17089.370000 0001 2190 316XDepartment of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2 Canada
| | - Elena N. Kitova
- grid.17089.370000 0001 2190 316XDepartment of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2 Canada
| | - Jeremy T. Nothof
- grid.17089.370000 0001 2190 316XDepartment of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2 Canada
| | - Akihiko Koizumi
- grid.17089.370000 0001 2190 316XDepartment of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2 Canada
| | - John S. Klassen
- grid.17089.370000 0001 2190 316XDepartment of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2 Canada
| | - Todd L. Lowary
- grid.17089.370000 0001 2190 316XDepartment of Chemistry, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB T6G 2G2 Canada ,grid.506934.d0000 0004 0633 7878Institute of Biological Chemistry, Academia Sinica, Academia Road, Section 2, #128, Nangang, Taipei, 11529 Taiwan ,grid.19188.390000 0004 0546 0241Institute of Biochemical Sciences, National Taiwan University, Section 4, #1, Roosevelt Road, Taipei, 10617 Taiwan
| | - Chris Whitfield
- grid.34429.380000 0004 1936 8198Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road E., Guelph, ON N1G 2W1 Canada
| | - Matthew S. Kimber
- grid.34429.380000 0004 1936 8198Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road E., Guelph, ON N1G 2W1 Canada
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3
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Nekvasilová P, Kulik N, Rychlá N, Pelantová H, Petrásková L, Bosáková Z, Cvačka J, Slámová K, Křen V, Bojarová P. How Site‐Directed Mutagenesis Boosted Selectivity of a Promiscuous Enzyme. Adv Synth Catal 2020. [DOI: 10.1002/adsc.202000604] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Pavlína Nekvasilová
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
- Department of Genetics and Microbiology Faculty of Science Charles University Viničná 5 CZ-12843 Praha 2 Czech Republic
- Department of Analytical Chemistry Faculty of Science Charles University Hlavova 2030/8. CZ-12843 Praha 2 Czech Republic
| | - Natalia Kulik
- Center for Nanobiology and Structural Biology Institute of Microbiology Czech Academy of Sciences Zámek 136 CZ-37333 Nové Hrady Czech Republic
| | - Nikola Rychlá
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
- Department of Health Care Disciplines and Population Protection Faculty of Biomedical Engineering Czech Technical University in Prague Nám. Sítná 3105 CZ-27201 Kladno Czech Republic
| | - Helena Pelantová
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
| | - Lucie Petrásková
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
| | - Zuzana Bosáková
- Department of Analytical Chemistry Faculty of Science Charles University Hlavova 2030/8. CZ-12843 Praha 2 Czech Republic
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry Czech Academy of Sciences Flemingovo nám. 2 CZ-16610 Praha 6 Czech Republic
| | - Kristýna Slámová
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
| | - Vladimír Křen
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
| | - Pavla Bojarová
- Institute of Microbiology Czech Academy of Sciences Vídeňská 1083 CZ-14220 Praha 4 Czech Republic
- Department of Health Care Disciplines and Population Protection Faculty of Biomedical Engineering Czech Technical University in Prague Nám. Sítná 3105 CZ-27201 Kladno Czech Republic
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4
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Škerlová J, Bláha J, Pachl P, Hofbauerová K, Kukačka Z, Man P, Pompach P, Novák P, Otwinowski Z, Brynda J, Vaněk O, Řezáčová P. Crystal structure of native β‐
N
‐acetylhexosaminidase isolated from
Aspergillus oryzae
sheds light onto its substrate specificity, high stability, and regulation by propeptide. FEBS J 2017; 285:580-598. [DOI: 10.1111/febs.14360] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/03/2017] [Accepted: 12/08/2017] [Indexed: 12/18/2022]
Affiliation(s)
- Jana Škerlová
- Institute of Organic Chemistry and Biochemistry The Czech Academy of Sciences Prague Czech Republic
- Institute of Molecular Genetics The Czech Academy of Sciences Prague Czech Republic
| | - Jan Bláha
- Department of Biochemistry Faculty of Science Charles University Prague Czech Republic
| | - Petr Pachl
- Institute of Organic Chemistry and Biochemistry The Czech Academy of Sciences Prague Czech Republic
| | - Kateřina Hofbauerová
- Institute of Microbiology The Czech Academy of Sciences Prague Czech Republic
- Institute of Physics Faculty of Mathematics and Physics Charles University Prague Czech Republic
| | - Zdeněk Kukačka
- Department of Biochemistry Faculty of Science Charles University Prague Czech Republic
- Institute of Microbiology The Czech Academy of Sciences Prague Czech Republic
| | - Petr Man
- Department of Biochemistry Faculty of Science Charles University Prague Czech Republic
- Institute of Microbiology The Czech Academy of Sciences Prague Czech Republic
| | - Petr Pompach
- Institute of Microbiology The Czech Academy of Sciences Prague Czech Republic
| | - Petr Novák
- Department of Biochemistry Faculty of Science Charles University Prague Czech Republic
- Institute of Microbiology The Czech Academy of Sciences Prague Czech Republic
| | | | - Jiří Brynda
- Institute of Organic Chemistry and Biochemistry The Czech Academy of Sciences Prague Czech Republic
- Institute of Molecular Genetics The Czech Academy of Sciences Prague Czech Republic
| | - Ondřej Vaněk
- Department of Biochemistry Faculty of Science Charles University Prague Czech Republic
| | - Pavlína Řezáčová
- Institute of Organic Chemistry and Biochemistry The Czech Academy of Sciences Prague Czech Republic
- Institute of Molecular Genetics The Czech Academy of Sciences Prague Czech Republic
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5
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Krejzová J, Kulik N, Slámová K, Křen V. Expression of human β-N-acetylhexosaminidase B in yeast eases the search for selective inhibitors. Enzyme Microb Technol 2016; 89:1-6. [PMID: 27233122 DOI: 10.1016/j.enzmictec.2016.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 02/29/2016] [Accepted: 03/07/2016] [Indexed: 11/27/2022]
Abstract
Human lysosomal β-N-acetylhexosaminidases from the family 20 of glycoside hydrolases are dimeric enzymes catalysing the cleavage of terminal β-N-acetylglucosamine and β-N-acetylgalactosamine residues from a broad spectrum of glycoconjugates. Here, we present a facile, robust, and cost-effective extracellular expression of human β-N-acetylhexosaminidase B in Pichia pastoris KM71H strain. The prepared Hex B was purified in a single step with 33% yield obtaining 10mg of the pure enzyme per 1L of the culture media. The enzyme was used in the inhibition assays with the known mechanism-based inhibitor NAG-thiazoline and a wide variety of its derivatives in the search for specific inhibitors of the human GH20 β-N-acetylhexosaminidases over the human GH84 β-N-acetylglucosaminidase, which was expressed, purified and used in the inhibition experiments as well. Moreover, enzyme-inhibitor complexes were analysed employing computational tools in order to reveal the structural basis of the results of the inhibition assays, showing the importance of water-mediated interactions between the enzyme and respective ligands. The presented method for the heterologous expression of human Hex B is robust, it significantly reduces the costs and equipment demands in comparison to the expression in mammalian cell lines. This will enhance accessibility of this human enzyme to the broad scientific community and may speed up the research of specific inhibitors of this physiologically important glycosidase family.
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Affiliation(s)
- Jana Krejzová
- Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Praha 4, Czech Republic; Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 5, CZ 16628 Praha 6, Czech Republic.
| | - Natallia Kulik
- Department of Structure and Function of Proteins, Institute of Microbiology, Czech Academy of Sciences, Zámek 136, CZ 37333 Nové Hrady, Czech Republic.
| | - Kristýna Slámová
- Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Praha 4, Czech Republic.
| | - Vladimír Křen
- Laboratory of Biotransformation, Institute of Microbiology, Czech Academy of Sciences, Vídeňská 1083, CZ 14220 Praha 4, Czech Republic.
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6
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Structural and Biochemical Insights into the Peptidoglycan Hydrolase Domain of FlgJ from Salmonella typhimurium. PLoS One 2016; 11:e0149204. [PMID: 26871950 PMCID: PMC4752226 DOI: 10.1371/journal.pone.0149204] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Accepted: 01/28/2016] [Indexed: 11/19/2022] Open
Abstract
FlgJ is a glycoside hydrolase (GH) enzyme belonging to the Carbohydrate Active enZyme (CAZy) family GH73. It facilitates passage of the bacterial flagellum through the peptidoglycan (PG) layer by cleaving the β-1,4 glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid sugars that comprise the glycan strands of PG. Here we describe the crystal structure of the GH domain of FlgJ from bacterial pathogen Salmonella typhimurium (StFlgJ). Interestingly, the active site of StFlgJ was blocked by the C-terminal α-helix of a neighbouring symmetry mate and a β-hairpin containing the putative catalytic glutamic acid residue Glu223 was poorly resolved and could not be completely modeled into the electron density, suggesting it is flexible. Previous reports have shown that the GH73 enzyme Auto from Listeria monocytogenes is inhibited by an N-terminal α-helix that may occlude the active site in similar fashion. To investigate if the C-terminus of StFlgJ inhibits GH activity, the glycolytic activity of StFlgJ was assessed with and without the C-terminal α-helix. The GH activity of StFlgJ was unaffected by the presence or absence of the α-helix, suggesting it is not involved in regulating activity. Removal of the C-terminal α-helix did, however, allow a crystal structure of the domain to be obtained where the flexible β-hairpin containing residue Glu223 was entirely resolved. The β-hairpin was positioned such that the active site groove was fully solvent-exposed, placing Glu223 nearly 21.6 Å away from the putative general acid/base residue Glu184, which is too far apart for these two residues to coordinate glycosidic bond hydrolysis. The mobile nature of the StFlgJ β-hairpin is consistent with structural studies of related GH73 enzymes, suggesting that a dynamic active site may be common to many GH73 enzymes, in which the active site opens to capture substrate and then closes to correctly orient active site residues for catalysis.
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7
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Slámová K, Krejzová J, Marhol P, Kalachova L, Kulik N, Pelantová H, Cvačka J, Křen V. Synthesis of Derivatized Chitooligomers using Transglycosidases Engineered from the Fungal GH20 β-N-Acetylhexosaminidase. Adv Synth Catal 2015. [DOI: 10.1002/adsc.201500075] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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8
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Halila S, Samain E, Vorgias CE, Armand S. A straightforward access to TMG-chitooligomycins and their evaluation as β-N-acetylhexosaminidase inhibitors. Carbohydr Res 2013; 368:52-6. [DOI: 10.1016/j.carres.2012.12.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 11/29/2012] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
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9
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Arcelli A, Bongini A, Porzi G, Rinaldi S. Ammonolysis of morpholine-2,5-diones: participation of the primary amide group. Part 2. J PHYS ORG CHEM 2012. [DOI: 10.1002/poc.1884] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Antonio Arcelli
- Dipartimento di Chimica “G. Ciamician”; Via Selmi 2 40126 Bologna Italy
| | | | - Gianni Porzi
- Dipartimento di Chimica “G. Ciamician”; Via Selmi 2 40126 Bologna Italy
| | - Samuele Rinaldi
- Dipartimento I.S.A.C.; Università Politecnica delle Marche; Via Brecce Bianche 60131 Ancona Italy
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10
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Slámová K, Bojarová P, Gerstorferová D, Fliedrová B, Hofmeisterová J, Fiala M, Pompach P, Křen V. Sequencing, cloning and high-yield expression of a fungal β-N-acetylhexosaminidase in Pichia pastoris. Protein Expr Purif 2012; 82:212-7. [PMID: 22266368 DOI: 10.1016/j.pep.2012.01.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 01/02/2012] [Accepted: 01/04/2012] [Indexed: 11/25/2022]
Abstract
The β-N-acetylhexosaminidase from Talaromyces flavus has a remarkable synthetic ability, processing even carbohydrates with various functionalities. Its broader use is partially hampered by low-yield production in the native fungus. Here, we present an optimized 3-day production of this enzyme in the eukaryotic host of Pichia pastoris, in ca 10-fold higher volume activity (10 U/ml) and close-to-perfect purity (one chromatographic step needed). Importantly, the recombinant enzyme features the same biochemical and catalytic properties, including the syntheses with derivatized carbohydrate substrates. This is the first example of the overexpression of a fungal β-N-acetylhexosaminidase by a single-cell producer in liquid medium. It represents a promising solution for wider biotechnological applications of this outstanding enzyme.
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Affiliation(s)
- Kristýna Slámová
- Institute of Microbiology, Center for Biocatalysis and Biotransformation, Academy of Sciences of the Czech Republic, Vídeňská 1083, CZ 14220, Prague 4, Czech Republic
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11
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Slámová K, Bojarová P, Petrásková L, Křen V. β-N-Acetylhexosaminidase: What's in a name…? Biotechnol Adv 2010; 28:682-93. [DOI: 10.1016/j.biotechadv.2010.04.004] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 04/17/2010] [Accepted: 04/24/2010] [Indexed: 01/28/2023]
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12
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Slámová K, Gažák R, Bojarová P, Kulik N, Ettrich R, Pelantová H, Sedmera P, Křen V. 4-Deoxy-substrates for β-N-acetylhexosaminidases: How to make use of their loose specificity. Glycobiology 2010; 20:1002-9. [DOI: 10.1093/glycob/cwq058] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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13
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Lairson LL, Henrissat B, Davies GJ, Withers SG. Glycosyltransferases: structures, functions, and mechanisms. Annu Rev Biochem 2008; 77:521-55. [PMID: 18518825 DOI: 10.1146/annurev.biochem.76.061005.092322] [Citation(s) in RCA: 1360] [Impact Index Per Article: 85.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Glycosyltransferases catalyze glycosidic bond formation using sugar donors containing a nucleoside phosphate or a lipid phosphate leaving group. Only two structural folds, GT-A and GT-B, have been identified for the nucleotide sugar-dependent enzymes, but other folds are now appearing for the soluble domains of lipid phosphosugar-dependent glycosyl transferases. Structural and kinetic studies have provided new insights. Inverting glycosyltransferases utilize a direct displacement S(N)2-like mechanism involving an enzymatic base catalyst. Leaving group departure in GT-A fold enzymes is typically facilitated via a coordinated divalent cation, whereas GT-B fold enzymes instead use positively charged side chains and/or hydroxyls and helix dipoles. The mechanism of retaining glycosyltransferases is less clear. The expected two-step double-displacement mechanism is rendered less likely by the lack of conserved architecture in the region where a catalytic nucleophile would be expected. A mechanism involving a short-lived oxocarbenium ion intermediate now seems the most likely, with the leaving phosphate serving as the base.
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Affiliation(s)
- L L Lairson
- Department of Chemistry, University of British Columbia, Vancouver, BC, Canada.
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14
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Macauley MS, Whitworth GE, Debowski AW, Chin D, Vocadlo DJ. O-GlcNAcase uses substrate-assisted catalysis: kinetic analysis and development of highly selective mechanism-inspired inhibitors. J Biol Chem 2005; 280:25313-22. [PMID: 15795231 DOI: 10.1074/jbc.m413819200] [Citation(s) in RCA: 297] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The post-translational modification of serine and threonine residues of nucleocytoplasmic proteins with 2-acetamido-2-deoxy-d-glucopyranose (GlcNAc) is a reversible process implicated in multiple cellular processes. The enzyme O-GlcNAcase catalyzes the cleavage of beta-O-linked GlcNAc (O-GlcNAc) from modified proteins and is a member of the family 84 glycoside hydrolases. The family 20 beta-hexosaminidases bear no apparent sequence similarity yet are functionally related to O-GlcNAcase because both enzymes cleave terminal GlcNAc residues from glycoconjugates. Lysosomal beta-hexosaminidase is known to use substrate-assisted catalysis involving the 2-acetamido group of the substrate; however, the catalytic mechanism of human O-GlcNAcase is unknown. By using a series of 4-methylumbelliferyl 2-deoxy-2-N-fluoroacetyl-beta-D-glucopyranoside substrates, Taft-like linear free energy analyses of these enzymes indicates that O-GlcNAcase uses a catalytic mechanism involving anchimeric assistance. Consistent with this proposal, 1,2-dideoxy-2'-methyl-alpha-D-glucopyranoso-[2,1-d]-Delta2'-thiazoline, an inhibitor that mimics the oxazoline intermediate proposed in the catalytic mechanism of family 20 glycoside hydrolases, is shown to act as a potent competitive inhibitor of both O-GlcNAcase (K(I) = 0.070 microm) and beta-hexosaminidase (K = 0.070 microm). A series of 1,2-dideoxy-2'-methyl-alpha-D-glucopyranoso-[2,1-d]-Delta2'-thiazoline analogues were prepared, and one inhibitor demonstrated a remarkable 1500-fold selectivity for O-GlcNAcase (K(I) = 0.230 microm) over beta-hexosaminidase (K(I) = 340 microm). These inhibitors are cell permeable and modulate the activity of O-GlcNAcase in tissue culture. Because both enzymes have vital roles in organismal health, these potent and selective inhibitors of O-GlcNAcase should prove useful in studying the role of this enzyme at the organismal level without generating a complex chemical phenotype stemming from concomitant inhibition of beta-hexosaminidase.
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Affiliation(s)
- Matthew S Macauley
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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15
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Böhm M, Vasella A. Probing the Conformational Changes in the Enzymatic Hydrolysis of 2-Acetamido-2-deoxy-β-D-glucopyranosides. Helv Chim Acta 2004. [DOI: 10.1002/hlca.200490229] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Honda Y, Kitaoka M, Hayashi K. Kinetic evidence related to substrate-assisted catalysis of family 18 chitinases. FEBS Lett 2004; 567:307-10. [PMID: 15178342 DOI: 10.1016/j.febslet.2004.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Revised: 05/02/2004] [Accepted: 05/04/2004] [Indexed: 11/26/2022]
Abstract
The hydrolytic reaction of family 18 chitinase has been considered to occur via substrate assisted catalysis. To kinetically investigate the enzyme reaction mechanism, we synthesized compounds designed to reduce the polarization of the carbonyl in N-acetyl group, GlcNAc-GlcN(TFA)-UMB (2) and GlcNAc-GlcN(TAc)-UMB (3). Kinetic parameters in the hydrolysis of these compounds by chitinase A from Serratia marcescens (ChiA) were compared with those from the hydrolysis of (GlcNAc)2-UMB (1). The kcat of 2 was 3.4% of 1, but the Km of 2 was 10-fold that of 1. In contrast, the kcat of 3 was only 0.3% of that of 1, and the two reactions had an identical Km. The drastic decreases in kcat were probably due to the weak nucleophilic activity of the C2-N-trifluoroacetamide and N-thioacetamide groups at reducing ends of compounds 2 and 3, respectively. These results indicate that the anchimeric assistance of the C2 N-acetamide group at GlcNAc plays a key role in the hydrolytic reactions catalyzed by family 18 chitinases.
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Affiliation(s)
- Yuji Honda
- National Food Research Institute, 2-1-12, Kannondai, Tsukuba, Ibaraki 305-8642, Japan
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17
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Lairson LL, Chiu CPC, Ly HD, He S, Wakarchuk WW, Strynadka NCJ, Withers SG. Intermediate trapping on a mutant retaining alpha-galactosyltransferase identifies an unexpected aspartate residue. J Biol Chem 2004; 279:28339-44. [PMID: 15075344 DOI: 10.1074/jbc.m400451200] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipopolysaccharyl-alpha-1,4-galactosyltransferase C (LgtC), a glycosyltransferase family 8 alpha-1,4-galactosyltransferase from Neisseria meningitidis, catalyzes the transfer of galactose from UDP galactose to terminal lactose-containing acceptor sugars with net retention of anomeric configuration. To investigate the potential role of discrete nucleophilic catalysis suggested by the double displacement mechanism generally proposed for retaining glycosyltransferases, the side chain amide of Gln-189, which is suitably positioned to act as the catalytic nucleophile of LgtC, was substituted with the more nucleophilic carboxylate-containing side chain of glutamate in the hope of accumulating a glycosyl-enzyme intermediate. The resulting mutant was subjected to kinetic, mass spectrometric, and x-ray crystallographic analysis. Although the K(m) for UDP-galactose is not significantly altered, the k(cat) was reduced to 3% that of the wild type enzyme. Electrospray mass spectrometric analysis revealed that a steady state population of the Q189E variant contains a covalently bound galactosyl moiety. Liquid chromatographic/mass spectrometric analysis of fragmented proteolytic digests identified the site of labeling not as Glu-189 but, surprisingly, as the sequentially adjacent Asp-190. However, the side chain carboxylate of Asp-190 is located 8.9 A away from the donor substrate in the available crystal structure. Kinetic analysis of a D190N mutant at this position revealed a k(cat) value 3000-fold lower than that of the wild type enzyme. A 2.6-A crystal structure of the Q189E mutant with bound uridine 5'-diphospho-2-deoxy-2-fluoro-alpha-d-galactopyranose revealed no significant perturbation of the mode of donor sugar binding nor of active site configuration. This is the first trapping of an intermediate in the active site of a retaining glycosyltransferase and, although not conclusive, implicates Asp-190 as an alternative candidate catalytic nucleophile, thereby rekindling a longstanding mechanistic debate.
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Affiliation(s)
- Luke L Lairson
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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