黄嘌呤氧化酶酶学性质及共价交联固定化

Enzymatic Properties of Xanthine Oxidase and Its Covalent Immobilization on Different Supports

研究了节杆菌Arthrobacter M3黄嘌呤氧化酶酶学性质,并利用修饰的琼脂糖介质及大孔阴离子交换树脂固定化黄嘌呤氧化酶,提高酶热稳定性。研究发现,该酶为异质二聚体,相对分子量为135 000;最适反应温度为37℃,最适反应pH为7.5。固定化结果表明,以修饰的琼脂糖介质共价交联固定化的酶热稳定性均优于大孔阴离子交换树脂类,其中以谷氨酸为连接臂的琼脂糖介质(Sepharose-Glu)固定化效果最佳。在50℃下保温3 h,相比于游离酶酶活仅剩余8.0%,Sepharose-Glu介质固定化的酶仍保留48.3%的酶活,半衰期提高了1.6倍,酸碱耐受性亦优于游离酶。

The enzymatic properties of xanthine oxidase （XOD） from Arthrobacter M3 were first investigated,and then modified sepharose 4B mediums and macroporous ion exchange resins were used to immobilize XOD in order to enhance the enzyme stability.The results showed that this enzyme was a heterodimer with a molecular weight of 135 000.The optimal reaction temperature and pH for XOD were 37 ℃ and 7.5,respectively.The stabilities of the covalently immobilized XOD on the modified sepharose 4B mediums were higher than that on macroporous ion exchange resins.Furthermore,the immobilized XOD on sepharose 4B-glutamate medium （Sepharose-Glu） showed the optimum stability.After incubation at 50 ℃ for 3 h,the immobilized XOD on Sepharose-Glu medium still maintained 48.3% of its initial activity,and the half-life of this immobilized enzyme increased by 160% compared to the free enzyme.In addition,acid-alkali tolerance of this immobilized XOD was also improved.