Glycosyltransferases: Structures, functions, and mechanisms

Research output: Contribution to journalLiterature review

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JournalANNUAL REVIEW OF BIOCHEMISTRY
DatePublished - 2008
Volume77
Number of pages35
Pages (from-to)521-555
Original languageEnglish

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.

    Research areas

  • carbohydrate-modifying enzymes, glycobiology, glycosylation, ion pair mechanisms, nucleophilic substitution, N-ACETYLGLUCOSAMINYLTRANSFERASE-I, COLI MALTODEXTRIN PHOSPHORYLASE, LIVER-GLYCOGEN PHOSPHORYLASE, RAY CRYSTAL-STRUCTURE, PASTEURELLA-MULTOCIDA SIALYLTRANSFERASE, RETAINING ALPHA-GALACTOSYLTRANSFERASE, DIMETHYLALLYL DIPHOSPHATE ISOMERASE, PHAGE BETA-GLUCOSYLTRANSFERASE, GROUP-B GLYCOSYLTRANSFERASES, BASE-FLIPPING MECHANISM

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