title: Purification and characterization of two extracellular beta-glucosidases from Trichoderma reesei.
abstract: A major beta-glucosidase I and a minor beta-glucosidase II were purified from culture filtrates of the fungus Trichoderma reesei grown on wheat straw. The enzymes were purified using CM-Sepharose CL-6B cation-exchange and DEAE Bio-Gel A anion-exchange chromatography steps, followed by Sephadex G-75 gel filtration. The isolated enzymes were homogeneous in SDS-polyacrylamide gel electrophoresis and isoelectric focusing. beta-Glucosidase I (71 kDa) was isoelectric at pH 8.7 and contained 0.12% carbohydrate; beta-glucosidase II (114 kDa) was isoelectric at pH 4.8 and contained 9.0% carbohydrate. Both enzymes catalyzed the hydrolysis of cellobiose and p-nitrophenyl-beta-D-glucoside (pNPG). The Km and kcat/Km values for cellobiose were 2.10 mM, 2.45.10(4) s-1 M-1 (beta-glucosidase I) and 11.1 mM, 1.68.10(3) s-1 M-1 (beta-glucosidase II). With pNPG as substrate the Km and kcat/Km values were 182 microM, 7.93.10(5) s-1 M-1 (beta-glucosidase I) and 135 microM, 1.02.10(6) s-1 M-1 (beta-glucosidase II). The temperature optimum was 65-70 degrees C for beta-glucosidase I and 60 degrees C for beta-glucosidase II, the pH optimum was 4.6 and 4.0, respectively. Several inhibitors were tested for their action on both enzymes. beta-Glucosidase I and II were competitively inhibited by desoxynojirimycin, gluconolactone and glucose.
authors.affiliation: Institute of Biochemistry, University of Graz, Austria.
authors.forename: H
authors.initials: H
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Hayn
authors.forename: H
authors.initials: H
authors.lastname: Esterbauer
mesh_terms: D002413:Cations, Divalent; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D013379:Substrate Specificity; D013816:Thermodynamics; D014242:Trichoderma / Q000201:enzymology*; D001617:beta-Glucosidase / Q000302:isolation & purification* / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D007527:Isoenzymes; D001617:beta-Glucosidase