Studies onβ-Glucosidases from Soybeans That Hydrolyze Daidzin and Genistin: Isolation and Characterization of an Isozyme

β-Glucosidases (A, B, and C) have been isolated from soybean cotyledons. The isolated enzyme is a β-Glucosidase-C forming a single band on CM-Sephadex C-50 ion exchange chromatography, and on Butyl-Toyopearl 650C and Sephadex G-150 gel filtration. The homogeneity of the purified enzyme was proved by SDS–polyacrylamide gel electrophoresis and isoelectric focusing. The molecular weight was estimated to be 81,000 and 36,000 by HPLC gel filtration on TSKgel G3000SWXL and SDS–polyacrylamide gel electrophoresis, respectively. The isoelectric point was estimated to be 6.68. The enzyme showed optimum activity at pH 4.5 and 45°C, and its pH range of action was 3.5–7.0. The enzyme was stable from pH 4.0 to 6.0 at 5°C. The enzyme hydrolyzed the isoflavone glucosides, daidzin, and genistin, to yield daidzein and genistein.