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- Publisher
- Annual Reviews
- Copyright
- Copyright © 2008 by Annual Reviews. All rights reserved
- ISSN
- 0066-4154
- eISSN
- 1545-4509
- DOI
- 10.1146/annurev.biochem.76.061005.092322
- pmid
- 18518825
- Publisher site
- See Article on Publisher Site
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.
Journal
Annual Review of Biochemistry – Annual Reviews
Published: Jul 7, 2008