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

A novel dioscin-glycosidase that specifically hydrolyzes multi-glycosides such as 3-O-alpha-L-(1 --> 4)-rhamnoside, 3-O-alpha-L-(1 --> 2)-rhamnoside, 3-O-alpha-L-(1 --> 4)-arabinoside and beta-D-glucoside on diosgenin was isolated from Absidia sp.d38 strain; and it was purified and characterized. The molecular weight of the new dioscin-glycosidase is about 55 kDa in SDS-PAGE. The the dioscin-glycosidase gradually hydrolyzes either 3-O-alpha-L-(1 --> 4)-Rha or 3-O-alpha-L-(1 --> 2)-Rha of dioscin to 3-O-alpha-L-Rha-beta-D-Glc-diosgenin; further rapidly hydrolyzes the other alpha-L-Rha of 3-O-alpha-L-Rha-beta-D-Glc-diosgenin to main intermediate products 3-O-beta-D-glc-diosgenin; and subsequently hydrolyzes intermediate products to final product of aglycone; the new enzyme also gradually hydrolyzes 3-O-alpha-L-(1 --> 4)-arabinoside, 3-O-alpha-L-(1 --> 2)-rhamnoside and beta-D-glucoside of [3-O-alpha-L-(1 --> 4)-Ara, 3-O-alpha-L-(1 --> 2)-Rha]-beta-D-Glc-diosgenin into final product diosgenin, exhibiting significant differences from previously reported glycosidases. The optimal temperature of the new dioscin-glycosidase is 40 degrees C and the optimal pH is 5.0. The activity of the new dioscin-glycosidase was not affected by the Na+, K+ and Mg2+ ions; it was significantly inhibited by the Cu2+ and Hg2+ ions; and it was slightly affected by the Ca2+ ions.