KINETIC MECHANISM OF BETA-GLUCOSIDASE FROM TRICHODERMA-REESEI QM-9414

β-Glucosidase is a key enzyme in the hydrolysis of cellulose to d-glucose. β-Glucosidase was purified from cultures of Trichoderma reesei QM 9414 grown on wheat straw as carbon source. The enzyme hydrolyzed cellobiose and aryl β-glucosides. The doulbe-reciprocal plots of initial velocity vs. substrate concentration showed substrate inhibition with cellobiose and salicin. However, when p-nitrophenyl β-d-glucopyranoside was the substrate no inhibition was observed. The corresponding kinetic parameters were: K = 1.09 ± 0.2 mM and V = 2.09 ± 0.52 μmol · min-1 · mg-1 for salicin; K = 1.22 ± 0.3 mM and V = 1.14 ± 0.21 μmol · min-1 · mg-1 for cellobiose; K = 0.19 ± 0.02 mM and V = 29.67 ± 3.25 μmol · in-1 · mg-1 fro p-nitrophenyl β-d-glucopyranoside. Studies of inhibition by products and by alternative product supported an Ordered Uni Bi mechanism for the reaction catalyzed by β-glucosidase on p-nitrophenyl β-d-glucopyranoside as substrate. Alternative substrates as salicin and cellobiose, a substrate analog such as maltose and a product analog such as fructose were competitive inhibitors in the p-nitrophenyl β-d-glucopyranoside hydrolysis. © 1990.