Glutamic acid 160 is the acid‐base catalyst of β‐xylosidase from Bacillus stearothermophilus T‐6: a family 39 glycoside hydrolase

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Abstract
A β‐xylosidase from Bacillus stearothermophilus T‐6 was cloned, overexpressed in Escherichia coli and purified to homogeneity. Based on sequence alignment, the enzyme belongs to family 39 glycoside hydrolases, which itself forms part of the wider GH‐A clan. The conserved Glu160 was proposed as the acid‐base catalyst. An E160A mutant was constructed and subjected to steady state and pre‐steady state kinetic analysis together with azide rescue and pH activity profiles. The observed results support the assignment of Glu160 as the acid‐base catalytic residue.