Purification and characterization of a beta-glucosidase from Polygonum tinctorium which catalyzes preferentially the hydrolysis of indican

An enzyme, beta-glucosidase, which hydrolyzes indican (indoxyl-beta-D-glucoside) was isolated in pure form from a plant, Polygonum tinctorium, and characterized. The enzyme showed specifically a low K-m for indican (0.34 mM). The enzyme reacted with some other beta-glucosides having aromatic groups but not with alpha-glucoside or other glycosides like galactoside. The activity was inhibited by several metal cations such as Cu2+ and by typical inhibitors for beta-glucosidase such as D-glucono-1,5-lactone although these inhibitors required high concentrations.