title: An unusual mechanism of glycoside hydrolysis involving redox and elimination steps by a family 4 beta-glycosidase from Thermotoga maritima.
abstract: Among the numerous well-characterized families of glycosidases, family 4 appears to be the anomaly, requiring both catalytic NAD+ and a divalent metal for activity. The unusual cofactor requirement prompted the proposal of a mechanism involving key NAD+-mediated redox steps as well as elimination of the glycosidic oxygen. Primary kinetic isotope effects for the 2- and 3-deutero substrate analogues, isotopic exchange with solvent, and structural analysis of a 6-phospho-beta-glucosidase, BglT (E.C. 3.2.1.6), provided evidence in support of the proposed mechanism, which has striking resemblances to that of the sugar dehydratases. Furthermore, analysis of the stereochemical outcome indicated that family 4 enzymes are retaining glycosidases.
authors.affiliation: Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z1.
authors.forename: Vivian L Y
authors.initials: VL
authors.lastname: Yip
authors.forename: Annabelle
authors.initials: A
authors.lastname: Varrot
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Davies
authors.forename: Shyamala S
authors.initials: SS
authors.lastname: Rajan
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Yang
authors.forename: John
authors.initials: J
authors.lastname: Thompson
authors.forename: Wayne F
authors.initials: WF
authors.lastname: Anderson
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Withers
mesh_terms: D005959:Glucosidases / Q000737:chemistry* / Q000378:metabolism*; D006027:Glycosides / Q000737:chemistry* / Q000378:metabolism*; D006868:Hydrolysis; D008958:Models, Molecular; D010084:Oxidation-Reduction; D020124:Thermotoga maritima / Q000201:enzymology*
chemical_list: D006027:Glycosides; D005959:Glucosidases; C066586:6-phospho-beta-glucosidase