Hydrolysis of genistin and daidzin by a -glucosidase purified from Lentinula edodes

We had studied the purification and characterization of β-glucosidase from Lentinula edodes, and its activity of hydrolyzing genistin and daidzin. The beta-glucosidase was extracted from an edible mushrooms L. edodes fruiting body and concentrated 26.5-fold by (NH4)2SO4 precipitation, followed by CM-Sephadex C-50 and Sephacryl S-300 HR chromatography. The purified enzyme showed a single 66 kd band on SDS-PAGE. The optimal enzyme activity occurred at 60°C and pH 4.0 in hydrolysis of genistin, daidzin and p-NPG. The enzyme activity was completely inhibited by 5 mM Ag+, Cu2+ or Al3+, respectively. The enzyme had apparent the Km values of 0.347, 0.070 and 0.150 mM and Vmax values of 84878, 225 and 639 nkat•mg of protein-1 for the hydrolysis of p-NPG, genistin and daidzin, respectively, at 60°C and pH 5.0. All tested organic solvents inhibited the β-glucosidase activity on hydrolysis of genistin and daidzin. The hydrolysis efficiency of daidzin and genistin could come up to 97 and 92%, respectively with enough enzyme addition. These experiments demonstrate that β-glucosidase from L. edodes has high activities for hydrolysis of daidzin and genistin, and are likely to be used in the transformation of isoflavone glucosides into aglucones.   Key words: Lentinula edodes, glucosidase, hydrolysis, daidzin, genistin.