Divergence of Catalytic Mechanism within a Glycosidase Family Provides Insight into Evolution of Carbohydrate Metabolism by Human Gut Flora

Tracey M. Gloster, Johan P. Turkenburg, Jennifer R. Potts, Bernard Henrissat, Gideon J. Davies

Research output: Contribution to journalArticlepeer-review

79 Citations (Scopus)

Abstract

Enzymatic cleavage of the glycosidic bond yields products in which the anomeric configuration is either retained or inverted. Each mechanism reflects the dispositions of the enzyme functional groups; a facet of which is essentially conserved in 113 glycoside hydrolase (GH) families. We show that family GH97 has diverged significantly, as it contains both inverting and retaining alpha-glycosidases. This reflects evolution of the active center; a glutamate acts as a general base in inverting members, exemplified by Bacteroides thetaiotaomicron alpha-glucosidase BtGH97a, whereas an aspartate likely acts as a nucleophile in retaining members. The structure of BtGH97a and its complexes with inhibitors, coupled to kinetic analysis of active-site variants, reveals an unusual calcium ion dependence. H-1 NMR analysis shows an inversion mechanism for BtGH97a, whereas another GH97 enzyme from B. thetaiotaomicron, BtGH97b, functions as a retaining alpha-galactosidase.

Original languageEnglish
Pages (from-to)1058-1067
Number of pages10
JournalChemistry and Biology
Volume15
Issue number10
DOIs
Publication statusPublished - 20 Oct 2008

Keywords

  • LACZ BETA-GALACTOSIDASE
  • BACTEROIDES-THETAIOTAOMICRON
  • ESCHERICHIA-COLI
  • ALPHA-GLUCOSIDASE
  • ACTIVE ENZYMES
  • HYDROLASES
  • MODEL
  • MANNOSIDASE
  • RESOLUTION
  • INHIBITION

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