来源于红球菌胆固醇氧化酶ChOG的异源表达、纯化及催化反应结构分析

The Expression,Purification and Structural Analysis of Cholesterol Oxidase ChOG

胆固醇氧化酶是胆固醇代谢过程中的关键酶,临床上用胆固醇氧化酶作为检测血清胆固醇含量的应用潜力巨大。将来源于红球菌Rhodococcus ruber的胆固醇氧化酶Ch OG,分别转化到大肠杆菌宿主BL21(DE3)和Rosetta(DE3)中,在不同条件下进行诱导表达,结果表明:BL21(DE3)菌株在诱导温度为16℃、IPTG浓度为0.1 mmol/L时,Ch OG可溶性表达量最高(0.49 mg/ml)。Ch OG的最适反应温度为30℃,最适反应p H为7.5。最适反应条件下,酶活性达到8.0 U/mg。利用TLC、HPLC对Ch OG催化产物胆甾-4-烯-3-酮进行了鉴定分析。三维结构及定点突变分析表明Glu406及Arg408、Glu261在进行胆固醇C3羟基的脱氢、质子传递,以及底物异构化方面发挥着重要作用。

Cholesterol oxidase is a key enzyme during cholesterol metabolism. It could be potential used to detect the cholesterol level in serum in clinical trials. The cholesterol oxidase from Rhodococcus ruber （ChOG） was transformed into BL21 （DE3） and Rosetta （DE3） for protein expression, and was induced at different conditions. The results showed that ChOG was overexpressed at 16 ℃ and 0. 1 mmol/L IPTG. The activity reached 8. 033 U/rag after purification with Ni-NTA superflow. The product cholest-5-en-3-one was characterized by TLC and HPLC, respectively. The structural analysis showed that Glu406, together with Arg408 and Glu261 played an important role during the dehydrogenation of cholesterol C3-OH, proton transfer, and isomerization.