Properties of a novel β-glucosidase from Fusarium proliferatum ECU2042 that converts ginsenoside Rg 3 into Rh 2

Abstract

A novel β-glucosidase from Fusarium proliferatum ECU2042 (FPG) was successfully purified to homogeneity with a 506-fold increase in specific activity. The molecular mass of the native purified enzyme (FPG) was estimated to be approximately 78.7 kDa, with two homogeneous subunits of 39.1 kDa, and the p I of this enzyme was 4.4, as measured by two-dimensional electrophoresis. The optimal activities of FPG occurred at pH 5.0 and 50 °C, respectively. The enzyme was stable at pH 4.0–6.5 and temperatures below 60 °C, and the deactivation energy ( E d) for FPG was 88.6 kJ mo1 −1. Moreover, it was interesting to find that although the purified enzyme exhibited a very low activity towards p-nitrophenyl β- d-glucoside (pNPG), and almost no activity towards cellobiose, a relatively high activity was observed on ginsenoside Rg 3. The enzyme hydrolyzed the 3-C, β-(1 → 2)-glucoside of ginsenoside Rg 3 to produce ginsenoside Rh 2, but did not sequentially hydrolyze the β- d-glucosidic bond of Rh 2. The K m and V max values of FPG for ginsenoside Rg 3 were 2.37 mM and 0.568 μmol (h mg protein) −1, respectively. In addition, this enzyme also exhibited significant activities towards various alkyl glucosides, aryl glucosides and several natural glycosides.