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Probing Synergy between Two Catalytic Strategies in the Glycoside Hydrolase O-GlcNAcase Using Multiple Linear Free Energy Relationships

Resource type
Date created
2009-08-28
Authors/Contributors
Abstract
Human O-GlcNAcase plays an important role in regulating the post-translational modification of serine and threonine residues with β-O-linked N-acetylglucosamine monosaccharide unit (O-GlcNAc). The mechanism of O-GlcNAcase involves nucleophilic participation of the 2-acetamido group of the substrate to displace a glycosidically linked leaving group. The tolerance of this enzyme for variation in substrate structure has enabled us to characterize O-GlcNAcase transition states using several series of substrates to generate multiple simultaneous free-energy relationships. Patterns revealing changes in mechanism, transition state, and rate-determining step upon concomitant variation of both nucleophilic strength and leaving group abilities are observed. The observed changes in mechanism reflect the roles played by the enzymic general acid and the catalytic nucleophile. Significantly, these results illustrate how the enzyme synergistically harnesses both modes of catalysis; a feature that eludes many small molecule models of catalysis. These studies also suggest the kinetic significance of an oxocarbenium ion intermediate in the O-GlcNAcase-catalyzed hydrolysis of glucosaminides, probing the limits of what may be learned using nonatomistic investigations of enzymic transition-state structure and offering general insights into how the superfamily of retaining glycoside hydrolases act as efficient catalysts.
Document
Identifier
DOI: 10.1021/ja904506u
Published as
Greig, I. R., Macauley, M. S., Williams, I. H., & Vocadlo, D. J. (2009). Probing Synergy between Two Catalytic Strategies in the Glycoside Hydrolase O-GlcNAcase Using Multiple Linear Free Energy Relationships. Journal of the American Chemical Society, 131(37), 13415–13422. https://doi.org/10.1021/ja904506u
Publication title
Journal of the American Chemical Society
Document title
Probing Synergy between Two Catalytic Strategies in the Glycoside Hydrolase O-GlcNAcase Using Multiple Linear Free Energy Relationships
Date
2009
Volume
131
Issue
37
First page
13415
Last page
13422
Copyright statement
Copyright is held by the author(s).
Scholarly level
Peer reviewed?
Yes
Language
English

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