毁灭柱孢菌中一种人参皂苷Rb1水解酶的纯化及酶学性质研究

通过DEAE-纤维素阴离子交换层析、30％～80％（NH3）2SO3盐析、Sepharose CL-6B凝胶过滤层析和Mono Q HR5／5阴离子交换层析，从毁灭枉孢菌培养液中部分纯化出一种能够水解人参皂苷Rb，的β-葡萄糖苷酶F-I。F—I具有较好的pH稳定性和热稳定性，在pH4．0～11．0范围内和55℃以下表现出良好的β-葡萄糖苷酶活性，其最适pH为5．0，最适温度为55℃。EDTA、Cu^2＋和Zn^2＋对该酶活性有较强的抑制作用。底物专一性分析表明，F—I能高特异性水解人工合成的底物pNPG，还能水解β-葡萄糖苷键连接的二糖如纤维二糖和龙胆二糖，说明此酶为一种β-葡萄糖苷酶。F—I对人参皂苷Rb1表现了较强的水解活性，而对人参皂苷Rb2和Rc的水解活性较低。该酶水解人参皂苷Rb1的路径为Rb1→Rd→F2→C—K。F—I对人参皂苷Rb1的这种高效水解为稀有人参皂苷的工业制备奠定了基础。

Purification and Enzymatic Characters of a Ginseng Saponin Rb1 Hydrolytic Enzyme from Cylindrocarpon destructans

A ginseng saponin(GS) Rb1-hydrolytic enzyme β-glucosidase(F-I) was partially purified from cultural broth of the phytopathogenic fungus Cylindrocarpon destructans by DEAE-cellulose anion exchange chromatography,30%~80%(NH4)2SO4 salting-out,Sepharose CL-6B gel filtration chromatography and Mono Q HR 5/5 anion exchange chromatography.F-I had fairly good pH and thermal stability,within the range of pH 4.0~11.0 and below 55 ℃,it demeaned fine β-glucosidase activity.The optimal pH and temperature of F-I were pH 5.0 and 55 ℃ respectively.EDTA,Zn2+,and Cu2+ inhibited strongly against its activity.Specificity analysis of substratum indicated that F-I could highly hydrolyze artificial synthetically substratum of pNPG,it could also hydrolyze disaccharides such as cellobiose and gentiobiose that linked by β-glucoside bond,thus explained that it was a β-glucosidase.F-I acquitted itself well as fairly strong hydrolysis activity on GS,but had low hydrolysis activity on Rb2 and Rc.The pathway of hydrolysis of GS was Rb1 → Rd → F2 → C-K.The high effective hydrolysis of F-I on GS laid a foundation for rare GS Rb1 preparation industry.