New dioscin-glycosidase hydrolyzing multi-glycosides of dioscin from Absidia strain

摘要

A novel dioscin-glycosidase that specifically hydrolyzes multi-glycosides, such as 3-O-α-L-(1→4)-rhamnoside, 3-O-α-L-(1→2)-rhamnoside, 3-O-α-L-(1→4)-arabinoside, and β-D-glucoside, on diosgenin was isolated from the Absidia sp.d38 strain, purified, and characterized. The molecular mass of the new dioscin-glycosidase is about 55 kDa based on SDS-PAGE. The dioscin-glycosidase gradually hydrolyzes either 3-O-α-L-(1→4)-Rha or 3-O-α-L-(1→2)- Rha from dioscin into 3-O-α-L-Rha-β-D-Glc-diosgenin, further rapidly hydrolyzes the other α-L-Rha from 3-O-α- L-Rha-β-D-Glc-diosgenin into the main intermediate products of 3-O-β-D-Glc-diosgenin, and subsequently hydrolyzes these intermediate products into aglycone as the final product. The enzyme also gradually hydrolyzes 3-O-α-L- (1→4)-arabinoside, 3-O-α-L-(1→2)-rhamnoside, and β-Dglucoside from [3-O-α-L-(1→4)-Ara, 3-O-α-L-(1→2)-Rha]- β-D-Glc-diosgenin into diosgenin as the final product, exhibiting significant differences from previously reported glycosidases. The optimal temperature and pH for the new dioscin-glycosidase is 40°C and 5.0, respectively. Whereas the activity of the new dioscin-glycosidase was not affected by Na~+, K~+, and Mg~(2+) ions, it was significantly inhibited by Cu~(2+) and Hg~(2+) ions, and slightly affected by Ca~(2+) ions.