The identification of the acid–base catalyst of α‐arabinofuranosidase from <i>Geobacillus stearothermophilus</i> T‐6, a family 51 glycoside hydrolase

Abstract

The α‐ L ‐arabinofuranosidase from Geobacillus stearothermophilus T‐6 (AbfA T‐6) belongs to the retaining family 51 glycoside hydrolases. The conserved Glu175 was proposed to be the acid–base catalytic residue. AbfA T‐6 exhibits residual activity towards aryl β‐ D ‐xylopyranosides. This phenomenon was used to examine the catalytic properties of the putative acid–base mutant E175A. Data from kinetic experiments, pH profiles, azide rescue, and the identification of the xylopyranosyl azide product provide firm support to the assignment of Glu175 as the acid–base catalyst of AbfA T‐6.