链霉菌M1033葡萄糖异构酶的分离纯化及其性质的研究

Purification and Properties of D-glucose Isomerase From Streptomyces M1033

链霉菌M1033菌株所产的葡萄糖异构酶培养液经二级(NH_4)_2SO_4沉淀、DEAE-Sephadex A50,Sephadex-G150柱层析分离纯化,可得到电泳均一的纯酶。该酶的全分子量为91000左右,由两个相同的亚基组成。其pI为4.3,经糖染色后证明并非糖蛋白;最适反应温度70℃,在该温度下分别以D-木糖和D-葡萄糖为底物,测得最适pH分别为8.0和8.3。该酶为金属激活酶。Co^(2+)和Mg^(2+)对该酶有激活作用,Ca^(2+)则使之几乎失活。金属离子的激活作用随底物而异。动力学研究表明,该酶对D-木糖有更大的亲和性。

D-Glucose Isomerase from Streptomyces M1033 is purified to electrphoretic homogeneity through ammonium sulfate fractionation, DEAE-sephadex A-50, and Sephadex G-150 column chromatography from the culture in which the cell debris are removed. The enzyme is made up of two identical subunits. Its molecular weight is approximately 91 000 as measured by gel filtration and pI is 4.3. The enzyme is proved not to be a glyeoprotein. At about 70℃ the enzyme retains optimum activity. At this temperature the pH optimum with respect to glucose and xylose are 8.0 and 8.3. The enzyme is most activated by Co^(2+) and Mg^(2+). A further study shows that the effect of the same metal ion on the enzyme changes with respect to different substrates.