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°C and pH 7.0,respectively.This xylose isomerase is alkali-tolerant and thermo-stable: the enzyme activity keep about 80% in 70℃ for 1h 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+.