Purification and characterization of a glycosidase with hydrolyzing multi-3-O-glycosides of spirostanol saponin activity from Gibberella intermedia

• Gibberella intermedia had ability to hydrolyze dioscin from DZW into diosgenin.
• A special glycosidase from G. intermedia was purified and characterized.
• The glycosidase showed the maximum activity at 50 °C and pH 8.0.
• The glycosidase was stable in the pH range of 5.0–8.0.
• The glycosidase exhibited high activity on dioscin, trillin, and polyphyllin VII.

The strain Gibberella intermedia WX12 preserved in our lab showed a strong ability to degrade dioscin from Dioscorea Zingiberensis C. H. Wright into diosgenin. The glycosidase enzyme of this strain was purified by a procedure consisting of ammonium sulfate fractionation, anion-exchange and hydrophobic chromatography and was named GiGly. This enzyme was a monomer with molecular mass of approximately 45 kDa. The optimal temperature and pH were 50 °C and 8.0, respectively. GiGly was stable in the pH range of 5.0–8.0 and retained 80% of its original activity at pH 7.0 for 12 h. In the presence of metal ions including Na+, K+ and Mg2+ slightly increased GiGly activity, and Fe2+, Fe3+, Cu2+ and Mn2+ notably inhibited the activity. Meanwhile, GiGly showed high substrate specificity for multi-3-O-glycosides of spirostanol saponins such as dioscin, trillin and polyphyllin VII, and was inactive toward the substrates with terminal groups of rhamnosyl, glucosyl, galactosyl of ginsenoside Re and saikosaponin A. GiGly from G. intermedia WX12 could only hydrolyze glycosidic bonds at the C-3 position on steroidal saponins, which have similar structure with dioscin, and can be transformed into diosgenin.

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