title: Glutamic acid 160 is the acid-base catalyst of beta-xylosidase from Bacillus stearothermophilus T-6: a family 39 glycoside hydrolase.
abstract: A beta-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.
authors.affiliation: Department of Food Engineering and Biotechnology, Technion Isreal Institute of Technology, Haifa 32000, Israel.
authors.forename: T
authors.initials: T
authors.lastname: Bravman
authors.forename: A
authors.initials: A
authors.lastname: Mechaly
authors.forename: S
authors.initials: S
authors.lastname: Shulami
authors.forename: V
authors.initials: V
authors.lastname: Belakhov
authors.forename: T
authors.initials: T
authors.lastname: Baasov
authors.forename: G
authors.initials: G
authors.lastname: Shoham
authors.forename: Y
authors.initials: Y
authors.lastname: Shoham
mesh_terms: D001386:Azides / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D002384:Catalysis; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000235:genetics; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D018698:Glutamic Acid / Q000235:genetics / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism; D006868:Hydrolysis / Q000187:drug effects; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity / Q000502:physiology; D014995:Xylosidases / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001386:Azides; D006027:Glycosides; C008646:4-nitrophenyl beta-D-xyloside; D018698:Glutamic Acid; D014995:Xylosidases; C026579:exo-1,4-beta-D-xylosidase