右旋糖酐对Savinase蛋白酶的化学修饰及酶学性质研究

Chemical Modification of Savinase by Dextran and Its Enzyme Properties

采用经高碘酸钠活化的右旋糖酐修饰Savinase蛋白酶,通过凝胶过滤层析(GPC)和圆二色性光谱(CD)表征了修饰后蛋白酶分子量和结构的变化,测试了修饰酶的反应动力学参数,并考察了温度及pH对修饰酶活力的影响。凝胶过滤层析结果证明修饰后蛋白酶分子量明显提高,圆二色光谱分析表明修饰后蛋白酶的结构有所改变,进一步验证了右旋糖酐和蛋白酶发生了反应。与原酶相比,修饰酶对底物的亲和力增加。原酶和修饰酶的最适温度均为40℃,在30℃～50℃之间修饰酶表现出优于原酶的热稳定性。在pH8.5～9.5之间,修饰酶的稳定性高于原酶。

Savinase was chemically modified using NaIO4 oxidised dextran.The molecular size and the secondary structure of modified Savinase were characterized by GPC and CD.The factors related with the activity of the modified Savinase,such as kinetic constant,temperature and pH value were studied and compared with those of native Savinase.GPC results showed that the molecular size of the protease increased after chemical modification.CD spectra revealed the difference between native and modified Savinase,which further demonstrated the conjugate of oxidized dextran and Savinase.Compared with the native Savinase,the modified one had a higher affinity to casein.The optimum reaction temperature for both of the protease was 40℃,and the modified Savinase had a better thermal stability at 30℃~50℃.The stability of modified Savinase is better than the native one at pH8.5~9.5.