银杏叶提取物和黄芪甲苷对牛晶状体醛糖还原酶的抑制作用

The inhibitory effects of Ginkgo biloba extract and Astragalus SaponinⅠ on aldose reductase extracted from bovine lens

目的观察并比较银杏叶提取物(Ginkgo bilobaextract,GBE)和黄芪甲苷(Astragalus SaponinⅠ,ASⅠ)对牛晶状体提取醛糖还原酶(aldose reductase,AR)活性的抑制作用。方法饱和硫酸铵溶液盐析法提取牛晶状体中的AR,Tris-甘氨酸SDS聚丙烯酰胺凝胶电泳鉴定所提取AR,Folin-酚法测定AR终提取液的蛋白浓度,DL-甘油醛-NADPH-紫外分光光度法测定牛晶状体AR活性,并以酶促动力学原理判断抑制类型并计算GBE和ASⅠ对AR的抑制常数。结果从电泳图判断所提蛋白质即为目标蛋白AR,收率为0.5%。GBE和ASⅠ对牛晶状体AR分别具有竞争性抑制和反竞争性抑制作用,其抑制常数分别为4.048μmol.L-1和6.218μmol.L-1。结论GBE和ASⅠ对牛晶状体AR的抑制类型不同,其抑制强度也有差异。

Objective To study the inhibitory mechanisms and inhibitory constants of Ginkgo biloba extract （GBE） and Astragalus Saponin Ⅰ （AS Ⅰ ） on aldose reductase （AR） extracted from bovine lens. Methods AR was extracted from bovine lens with saturated ammonium sulfate by salting out method. The identity of AR was confirmed by electrophoresis. The protein concentration of AR was determined by Folin - hydroxybenzene method. According to the principle of enzymatic - kinetic, the types of AR - inhibition of GBE and AS Ⅰ were determined, and their inhibitory constants were calculated. Results The protein extracted from bovine lens was confirmed to be AR, with a yield being about 0.5 %. The AR - inhibition of GBE was competitive in type, with its Ki being 4.048 μmol· L^-1, while that of AS Ⅰ was uncompetitive in type with a Ki of 6. 218 μmol· L^-1. Conclusion The inhibitions of GBE and AS Ⅰ on AR are of different mechanisms.