Purification and properties of a stable β-glucosidase from an extremely thermophilic anaerobic bacterium
- 1 May 1987
- journal article
- Published by Portland Press Ltd. in Biochemical Journal
- Vol. 243 (3), 779-787
- https://doi.org/10.1042/bj2430779
Abstract
A beta-glucosidase (EC 3.2.1.21) was purified to homogeneity from cell-free extracts of an extremely thermophilic anaerobic bacterium. The enzyme has an Mr of 43,000 as determined by molecular-exclusion chromatography, has a pI of 4.55 and shows optimum activity at pH 6.2. The enzyme is active against a wide range of aryl beta-glycosides and beta-linked disaccharides, with beta-galactosidase activity only slightly less than beta-glucosidase activity, and significant beta-xylosidase activity. Lineweaver-Burk plots for p-nitrophenyl beta-glucoside, o-nitrophenyl beta-glucoside and cellobiose substrates are biphasic concave-downwards. Inhibition of the beta-glucosidase by substrates and glucose is negligible. Thermal inactivation follows first-order kinetics, with t1/2 (65 degrees C) 45 h, t1/2 (75 degrees C) 47 min and t1/2 (85 degrees C) 1.4 min and a deactivation energy of 380 kJ/mol at pH 6.2. At pH 7.0, which is the optimum pH for thermostability, t1/2 (75 degrees C) is 130 min. At 75 degrees C, at pH 6.2, the thermostability is enhanced about 8-fold by 10% (w/v) glycerol, about 6-fold by 0.2 M-cellobiose and about 3-fold by 5 mM-dithiothreitol and 5 mM-2-mercaptoethanol.Keywords
This publication has 33 references indexed in Scilit:
- Stability of the endo-β-1, 4-glucanase and β-1, 4-glucosidase from Bacteroides succinogenesCanadian Journal of Microbiology, 1982
- Cellulolytic activity of the rumen bacterium Bacteroides succinogenesCanadian Journal of Microbiology, 1981
- Ultrasensitive Stain for Proteins in Polyacrylamide Gels Shows Regional Variation in Cerebrospinal Fluid ProteinsScience, 1981
- Cellulolytic enzyme system of Acetivibrio cellulolyticusCanadian Journal of Microbiology, 1981
- Stability of the Cellulase of Trichoderma reesei under use conditionsBiotechnology & Bioengineering, 1980
- Characterization and purification of thermostable β-glucosidase from Clostridium thermocellumBiochemical and Biophysical Research Communications, 1979
- Slow Transitions and Hysteretic Behavior in EnzymesAnnual Review of Biochemistry, 1979
- A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye BindingAnalytical Biochemistry, 1976
- Partial purification and properties of a β-glucosidase from Erwinia herbicola Y46Canadian Journal of Microbiology, 1975
- The β-glucosidase system of the thermophilic fungus Chaetomium thermophile var. Coprophile n. var.Biochimica et Biophysica Acta (BBA) - General Subjects, 1973