Thioglycoside hydrolysis catalyzed by {beta}-glucosidase
- Department of Chemistry, Tulane University, New Orleans, LA 70118 (United States)
Sweet almond {beta}-glucosidase (EC 3.2.1.21) has been shown to have significant thioglycohydrolase activity. While the K{sub m} values for the S- and O-glycosides are similar, the k{sub cat} values are about 1000-times lower for the S-glycosides. Remarkably, the pH-profile for k{sub cat}/K{sub m} for hydrolysis of p-nitrophenyl thioglucoside (pNPSG) shows the identical dependence on a deprotonated carboxylate (pK{sub a} 4.5) and a protonated group (pK{sub a} 6.7) as does the pH-profile for hydrolysis of the corresponding O-glycoside. Not surprisingly, in spite of the requirement for the presence of this protonated group in catalytically active {beta}-glucosidase, thioglucoside hydrolysis does not involve general acid catalysis. There is no solvent kinetic isotope effect on the enzyme-catalyzed hydrolysis of pNPSG.
- OSTI ID:
- 21032943
- Journal Information:
- Biochemical and Biophysical Research Communications, Journal Name: Biochemical and Biophysical Research Communications Journal Issue: 3 Vol. 362; ISSN 0006-291X; ISSN BBRCA9
- Country of Publication:
- United States
- Language:
- English
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