Akao T, Akao T, Hattori M, Namba T, Kobashi K
J Biochem. 1986 May;99(5):1425-31. doi: 10.1093/oxfordjournals.jbchem.a135612.
Ruminococcus sp. PO1-3 obtained from human intestinal flora is able to reduce dehydrocholate as well as 3-ketoglycyrrhetinate. From this bacterium dehydrocholate- and 3-ketoglycyrrhetinate-reducing activities were purified one thousand-fold together with 3-ketocholanate-reducing and 3-beta-hydroxyglycyrrhetinate (glycyrrhetic acid) oxidizing activities by means of Matrex Red A, Sephadex G-200 and Octyl-Sepharose column chromatography. The purified enzyme catalyzed the reduction of dehydrocholic acid to 3 beta-hydroxy-7,12-diketocholanic acid and of 3-ketocholanic acid to 3 beta-hydroxycholanic acid. Studies on substrate specificity revealed that the enzyme had absolute specificity for the beta-configuration of a hydroxyl group at the 3 position of bile acid and steroids having no double bond in the A/B ring. This enzyme was neither beta-hydroxysteroid dehydrogenase [EC 1.1.1.51] nor 3 beta-hydroxy-delta 5-steroid dehydrogenase [EC 1.1.1.145], but a novel type of enzyme, defined as 3 beta-hydroxysteroid dehydrogenase.
从人体肠道菌群中分离得到的瘤胃球菌属PO1-3能够还原脱氢胆酸盐以及3-酮基甘草次酸。通过Matrex Red A、Sephadex G-200和辛基-琼脂糖柱色谱法，从该细菌中纯化出脱氢胆酸盐还原活性、3-酮基甘草次酸还原活性、3-酮基胆酸还原活性以及3-β-羟基甘草次酸（甘草次酸）氧化活性，纯化倍数达1000倍。纯化后的酶催化脱氢胆酸还原为3-β-羟基-7,12-二酮胆酸，以及3-酮基胆酸还原为3-β-羟基胆酸。对底物特异性的研究表明，该酶对胆汁酸3位羟基的β构型以及A/B环中无双键的类固醇具有绝对特异性。这种酶既不是β-羟基类固醇脱氢酶[EC 1.1.1.51]，也不是3-β-羟基-δ5-类固醇脱氢酶[EC 1.1.1.145]，而是一种新型酶，定义为3-β-羟基类固醇脱氢酶。
