右旋糖酐对草酸脱羧酶的修饰研究

Study on chemical modification of oxalate decarboxylase by dextran

草酸脱羧酶(Oxdc)具有预防和治疗草酸钙结石症的应用前景,为提高其稳定性,改善其应用性能,本文采用高碘酸钠活化右旋糖酐(Dextran)对Oxdc进行化学修饰,并初步优化修饰条件:当高碘酸钠/右旋糖酐质量比为1∶1,右旋糖酐/Oxdc质量比为200∶1,修饰反应6h时,修饰率为93.2%,酶活回收率55.8%。聚丙烯酰胺凝胶电泳(SDSPAGE)和红外光谱(IR)分析结果证明右旋糖酐和草酸脱羧酶成功共价结合。同时,比较纯化的草酸脱羧酶(Oxdc)和右旋糖酐修饰的草酸脱羧酶(Dextran-Oxdc)的部分酶学性质发现,Dextran-Oxdc的最适反应pH、热稳定性及对胰蛋白酶的耐受性都明显提高,说明经过修饰的草酸脱羧酶稳定性显著增强。

In order to improve the stability of oxalate decarboxylase （Oxdc）and improve its applicationperformance,oxalate decarboxylase was modified by dextran which was firstly activated by sodium periodate.Themodified conditions were preliminary optimized as follows,the mass ratio of sodium periodate/dextran 1：1, themass ratio of dextran/Oxdc 200： 1, reaction for 6h.Under the optimized conditions,93.2% of the modification ratioand 55.8% recovery of the enzymatic activity were achieved.The results of SDS-PAGE and IR indicated thatdextran covalently combined with Oxdc. Compared with the wild oxalate decarboxylase （ Oxdc）, the enzymaticproperties of modified oxalate decarboxylase（Dextran-Oxdc）such as adaptation of pH,thermal stability and theresistance to trypsin had improved obviously,which illustrated that stabilities of Oxdc significantly enhanced aftermodification.