化学修饰对嗜水气单胞菌弹性蛋白酶活性及稳定性的影响

Effects of medical modification on elastase activity and stability of Aeromonas hydrophila

用10ku的截流膜超滤、30％～60％的硫酸铵分级沉淀、凝胶过滤层析和阴离子交换层析，获得纯化的嗜水气单胞菌胞外弹性蛋白酶。SDS-PAGE显示，该酶是分子量约为33ku的单体蛋白。用活化的右旋糖酐及单甲氧聚乙二醇（MPEG）分别对纯化的嗜水气单胞菌弹性蛋白酶进行化学修饰。修饰后的酶与原酶相比，修饰酶保留了天然酶的活性，两种修饰酶活性均能保留在60％以上，用MPEG修饰酶的保留活性更高（85．5％），而且两种修饰酶在耐热性、耐酸性等方面都优于天然酶，但修饰后酶的最适pH没变。修饰酶较天然酶稳定，具有较高的实用意义。

The elastase of Aerornonas hydrophila strain J-1 was successfully purified by uhrafihration through 10 ku nominal molecular weight of cut-off membrane, 30% ~ 60% ammnium sulfate fractionation, anion - exchange chromatography and sephaceryl chromatography. The results of SDS-PAGE analysis showed that the elastase was 33 ku of monomeric protein. The purified elastase was modified by two medical modifications （dextranT-40 and monomethoxy polyethylene glycol） to enhance thermostability and acid stability. Two modified enzymes retained their catalytic activity over 60% and were more stable than native forms against high temperature and low pH, especially MPEG - modified enzyme. However, the optimal reaction pH was not affected. Our results revealed that modified enzymes had higher practicality than native forms.