Properties of a novel β-glucosidase from Fusarium proliferatum ECU2042 that converts ginsenoside Rg3 into Rh2

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 pI 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 (Ed) 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 Rg3. The enzyme hydrolyzed the 3-C, β-(1 → 2)-glucoside of ginsenoside Rg3 to produce ginsenoside Rh2, but did not sequentially hydrolyze the β-d-glucosidic bond of Rh2. The Km and Vmax values of FPG for ginsenoside Rg3 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.