Fermentation Technology Division, Central Drug Research Institute, Lucknow 226 001, Uttar Pradesh, India.
Appl Biochem Biotechnol. 2011 Nov;165(5-6):1414-26. doi: 10.1007/s12010-011-9360-6. Epub 2011 Sep 10.
An extracellular cholesterol oxidase (cho) enzyme was isolated from the Streptomyces parvus, a new source and purified 18-fold by ion exchange and gel filtration chromatography. Specific activity of the purified enzyme was found to be 20 U/mg with a 55 kDa molecular mass. The enzyme was stable at pH 7.2 and 50 °C. The enzyme activity was inhibited in the presence of Pb(2+), Ag(2+), Hg(2+), and Zn(2+) and enhanced in the presence of Mn(2+). The enzyme activity was inhibited by the thiol-reducing reagents (DTT, β-mercaptoethanol), suggesting that disulfide linkage is essential for the enzyme activity. The enzyme activity was found to be maximum in the presence of Triton X-100 and X-114 detergents whereas sodium dodecyl sulfate fully inactivated the enzyme. The enzyme showed moderate stability towards all organic solvents except acetone, benzene, chloroform and the activity increased in the presence of isopropanol and ethanol. The K(m) value for the oxidation of cholesterol by this enzyme was 0.02 mM.
从短小链霉菌中分离到一种细胞外胆固醇氧化酶（cho）酶，这是一种新的来源，并通过离子交换和凝胶过滤层析进行了 18 倍的纯化。发现纯化酶的比活为 20 U/mg，分子量为 55 kDa。该酶在 pH 7.2 和 50°C 下稳定。酶活性在存在 Pb(2+)、Ag(2+)、Hg(2+)和 Zn(2+)时受到抑制，在存在 Mn(2+)时增强。酶活性被巯基还原试剂（DTT、β-巯基乙醇）抑制，表明二硫键连接对于酶活性是必需的。该酶在 Triton X-100 和 X-114 洗涤剂存在下的活性最高，而十二烷基硫酸钠则完全使酶失活。该酶对除丙酮、苯、氯仿以外的所有有机溶剂均具有中等稳定性，在异丙醇和乙醇存在下活性增加。该酶氧化胆固醇的 K(m)值为 0.02 mM。
