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.

Key words:

• active site
• β-d-glucosidase
• β-d-fucosidase
• Dalbergia cochinchinensis