New Dioscin-Glycosidase Hydrolyzing Multi-Glycosides of Dioscin from Absidia Strain

A novel dioscin-glycosidase that specifically 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 the sp.d38 strain, purified, and characterized. The mass of the new dioscin-glycosidase is about 55 kDa based on SDS-PAGE. The dioscin-glycosidase gradually hydrolyzes either 3-O-alpha-L-(1-->4)-Rha or 3-O-alpha-L-(1-->2)-Rha from dioscin into 3-O-alpha-L-Rha-beta-D-Glc-diosgenin, further rapidly hydrolyzes the other alpha-L-Rha from 3-O-alpha-L-Rha-beta-D-Glc-diosgenin into the main intermediate products of 3-O-beta-D-Glc-diosgenin, and subsequently hydrolyzes these intermediate products into aglycone as the final product. The enzyme also gradually hydrolyzes 3-O-alpha-L-(1-->4)-arabinoside, 3-O-alpha-L-(1-->2)-rhamnoside, and beta-D-glucoside from [3-O-alpha-L-(1-->4)-Ara, 3-O-alpha-L-(1-->2)-Rha]-beta-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 degrees C and 5.0, respectively. Whereas the activity of the new dioscin-glycosidase was not affected by Na+, K+, and Mg2+ ions, it was significantly inhibited by Cu2+ and Hg2+ ions, and slightly affected by Ca2+ ions.