Evidence for a Single Active Site in β-D-Glucosidase/β-D-Fucosidase from Dalbergia cochinchinensis Seeds

Abstract

Kinetic analyses have been done on the hydrolysis of p-nitrophenyl β-D-glucoside (PNPG) and P-nitrophenyl β-D-fucoside (PNPF) by the β-D-glucosidase/β-D-fucosidase enzyme from Thai Rosewood (Dalbergia cochinchinensis Pierre). PNPF showed a competitive inhibition of PNPG hydrolysis with a K_i of 0.42 mM. Hydrolysis of mixtures of PNPG and PNPF at fractional ratios ranging from 0 to 1 showed Lineweaver-Burk plots intermediate between the two extremes. The apparent K_m and apparent V_max at each fractional ratio showed good correspondence with the theoretical curves predicted for the existence of a single common active site for the hydrolysis of the two substrates.