关键词: 柴胡皂苷糖苷酶; Aspergillus oryzae c42菌株; 柴胡皂苷A; 柴胡皂苷B2

Abstract:

Radix bupleuri, a well-known traditional Chinese herb-drug, is often used to treat common cold with fever. One of the major physiologically active ingredients in radix bupleuri is saikosaponin which has the properties of anti-inflammation, anti-hypersusceptibility, anti-thrombus. The natural structures of saikosaponins are not suitable for physiological or pharmacological effects, the enzymatic transforming generally improves the bioactivity of natural productions. In this paper, a new special saikosaponin-glycosidase hydrolyzing 3-O-β-(1→3)-glucoside and 3-O-β-fucoside of saikosaponin A or B2 was isolated from Aspergillus oryzae c42 strain, purified and characterized. The methods of centrifugation, ammonium sulfate precipitation, ion-exchange chromatography on DEAE-cellulose column and vertical slab polyacrylamide gel electrophoresis(PAGE) were used to purify the enzyme, and its partial characteristics were studied. The molecular weight of saikosaponin-glycosidase was about 58000 by SDS-PAGE. The enzyme hydrolyzed 3-O-β-(1→3)-glucoside of saikosaponin A or B2 into 3-O-β-fucoside-saikosapogenin A or B2, and further hydrolyzed 3-O-β-fucoside of 3-O-β-fucoside-saikosapogenin A or B2 into their aglycone(saikosapogenin A or B2) exhibiting significant differences from all previously reported glycosidases. The optimum temperature of the saikosaponin-glycosidase was 40 ℃; the optimum pH was 5.0. The activity of this enzyme was not apparently affected by Na⁺ and K⁺ ions, but it was significantly inhibited by Cu²⁺, Hg²⁺ and Ag⁺ ions; and slightly affected by Ca²⁺ and Mg²⁺ ions. Further study on saikosaponin-glycosidase will bring new insight to the understanding of glycosidases.

Key words: Saikosaponin-glycosidase; Aspergillus oryzae c42 strain; Saikosaponin A; Saikosaponin B2