一株嗜热菌木糖异构酶的纯化与性质研究

摘要

研究了1株嗜热菌(Anoxybacillus flavithermus)所产木糖异构酶的分离纯化以及酶学性质.结果表明,经硫酸铵沉淀、Sephadex G-75凝胶过滤、纤维素DE-52弱阴离子交换柱和Q Sepharose Fast Flow 强阴离子交换层析得到的木糖异构酶,分子量约为181 ku,由4个相同分子量的亚基组成.酶反应的最适温度为80℃,最适为pH为7.0且最适pH范围宽泛,pH6.0～11.0酶反应活性能保持80%左右.该酶热稳定性及耐碱性能良好,70℃保温1 h后酶活仍能保持近80%左右;pH5.0～8.0保温1 h后酶活仍能保持近80%以上,甚至pH12.0保温1 h后酶活性仍能保持40%左右.Mn2+ 和Co2+ 对酶活性有明显促进作用,Zn2+、Cu2+以及Al3+对酶活性有一定程度的抑制.%A xylose isomerase produced by thermophilic bacterium Anoxybacillus flavithermus was purified using Sephadex G- 75 gel filtration, DEAE-cellulose anion exchange chromatography and Q Sepharose Fast Flow anion exchange chromatography. The estimated molecular mass of the purified xylose isomerase was 181 ku and was made up of four sub-groups. The optima temperature and pH of enzymatic reaction were 80℃ and pH 7. 0, respectively. This xylose isomerase is alkali- tolerant and thermo-stable: the enzyme activity keep about 80％ in 70℃ for lh and keep about 80％ in pH5. 0 ～ 8.0 for 1 h, even keep about 40％ in pH12.0 for 1 h. The enzyme was mainly activated by Mn2+ and Co2+ but was mainly restrained by Zn2+ , Cu2+ and Al3+.