Hara A, Nakayama T, Nakagawa M, Inoue Y, Tanabe H, Sawada H
Department of Biochemistry, Gifu Pharmaceutical University.
J Biochem. 1987 Dec;102(6):1585-92. doi: 10.1093/oxfordjournals.jbchem.a122208.
The kinetic mechanism of two major monomeric 17 beta-hydroxysteroid dehydrogenases from mouse liver cytosol was studied at pH 7 in both directions with NADP(H) and three steroid substrates: testosterone, 5 beta-androstane-3 alpha, 17 17 beta-diol, and estradiol-17 beta. In each case the reaction mechanism of the two enzymes was sequential, and inhibition patterns by-products and dead-end inhibitors were consisted with an ordered bi bi mechanism with the coenzyme binding to the free enzyme, although there was difference in affinity and maximum velocity for the steroidal substrates between the two enzymes. Binding studies of the coenzyme and substrate indicate the binding of coenzyme to the free enzyme, in which 1 mol of NADPH binds to 1 mol of each monomeric enzyme. The 4-pro-R-hydrogen atom of NADPH was transferred to the alpha-face of the steroid molecule by the two enzymes.
在pH 7条件下，利用NADP(H)以及三种甾体底物：睾酮、5β-雄甾烷-3α,17β-二醇和雌二醇-17β，对来自小鼠肝脏胞质溶胶的两种主要单体17β-羟基类固醇脱氢酶的动力学机制进行了双向研究。在每种情况下，两种酶的反应机制都是顺序性的，副产物和终产物抑制剂的抑制模式符合辅酶与游离酶结合的有序双双机制，尽管两种酶对甾体底物的亲和力和最大反应速度存在差异。辅酶和底物的结合研究表明辅酶与游离酶结合，其中1摩尔NADPH与1摩尔每种单体酶结合。两种酶都将NADPH的4-pro-R-氢原子转移到甾体分子的α面。
