Premium
Biochemical identification of the catalytic residues of a glycoside hydrolase family 120 β‐xylosidase, involved in xylooligosaccharide metabolisation by gut bacteria
Author(s) -
Cecchini Davide A.,
Fauré Régis,
Laville Elisabeth,
Potocki-Veronese Gabrielle
Publication year - 2015
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2015.08.012
Subject(s) - glycoside hydrolase , chemistry , hydrolysis , glycoside , biochemistry , enzyme , mutant , hydrolase , stereochemistry , gene
The β‐xylosidase B from Bifidobacterium adolescentis ATCC15703 belongs to the newly characterized family 120 of glycoside hydrolases. In order to investigate its catalytic mechanism, an extensive kinetic study of the wild‐type enzyme and mutants targeting the three highly conserved residues Asp 393 , Glu 416 and Glu 364 was performed. NMR analysis of the xyloside hydrolysis products, the change of the reaction rate‐limiting step for the Glu 416 mutants, the pH dependency of E416A activity and its chemical rescue allowed to demonstrate that this GH120 enzyme uses a retaining mechanism of glycoside hydrolysis, Glu 416 playing the role of acid/base catalyst and Asp 393 that of nucleophile.