Isolation and characterization of dioscin-α-l-rhamnosidase from bovine liver

• α-l-Rhamnosidase from bovine liver was isolated and purified.
• Dioscin was converted into diosgenyl-O-β-d-glucopyranoside by biotransforming with α-l-rhamnosidase.
• The effects of metal ions were investigated on bovine liver α-l-rhamnosidase.
• The following metal ions, Fe3+, Cu2+, Zn2+ and 10 mM Ca2+ showed inhibitory effects on the enzyme. Mg2+ exhibited the activated action.
• An dioscin-α-l-rhamnosidase with molecular mass of 75 kDa displayed optimum activity at 42 °C, pH 7, 4 h, and 2% of substrate concentration.

A novel dioscin-α-l-rhamnosidase was isolated and purified from fresh bovine liver. The activity of the enzyme was tested using diosgenyl-2,4-di-O-α-l-rhamnopyranosyl-β-d-glucopyranoside as a substrate. It was cleaved by the enzyme to two compounds, rhamnoses and diosgenyl-O-β-d-glucopyranoside. The optimal conditions for enzyme activity were that temperature was at 42 °C, pH was at 7, reaction time was at 4 h, and the substrate concentration was at 2%. Furthermore, metal ions such as Fe3+, Cu2+, Zn2+, Ca2+ and Mg2+ showed different effects on the enzyme activity. Mg2+ acted as an activator whereas Cu2+, Fe3+, and Zn2+ acted as strong inhibitors in a wide range of concentrations from 0 to 200 mM. It was interesting that Ca2+ played a role as an inhibitor when its concentration was at 10 mM and acted as an activator at the other concentrations for the enzyme. Moreover, the molecular weight of enzyme was determined as 75 kDa.

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