Purification and Some Properties of a β-Glucosidase from Trichoderma harzianum Type C-4

Abstract

Type C-4 strain of Trichoderma harzianum was isolated as a microorganism with high cellulolytic activity. β-Glucosidase is involved in the last step of cellulose saccharification by degrading cellobiose to glucose, and plays an important role in the cellulase enzyme system with a synergic action with endoglucanase and cellobiohydrolase for cellulose degradation. β-Glucosidase from T. harzianum type C-4 was purified to homogeneity through Sephacryl S-300, DEAE-Sephadex A-50, and Mono P column chromatographies. It was a single polypeptide with the molecular mass of 75,000 by SDS-PAGE. The enzyme was very active at pH 5.0 and 45°C. No significant inhibition was observed in the presence of metal ions, thiol reagents, or EDTA. The enzyme was stable in the presence of 5% ox gall and digestive enzymes. p-Nitrophenyl-β-D-cellobioside worked as a substrate for the enzyme as much as p-nitrophenyl-β-glucopyranoside. Glucose and gluconolactone showed competitive inhibition with a Ki, of 1 mM and 1.8 μM. respectively, while galactose, mannose, and xylose did not inhibit the enzyme significantly.