Baker M E
Department of Medicine, University of California, San Diego, La Jolla 92093-0623.
Steroids. 1994 Apr;59(4):248-58. doi: 10.1016/0039-128x(94)90109-0.
Amino acid sequence comparisons have revealed that mammalian 11 beta-hydroxysteroid and 17 beta-hydroxysteroid dehydrogenases and bacterial 3 alpha, 20 beta- and 3 beta-hydroxysteroid dehydrogenases are homologs; that is, these enzymes are descended from a common ancestor. These steroid dehydrogenases are also homologous to human 15-hydroxyprostaglandin dehydrogenase and to proteins found in Rhizobia, bacteria that form nitrogen-fixing nodules in the roots of legumes. We constructed a multiple sequence alignment of these proteins, which, when combined with the recently determined tertiary structure of Streptomyces hydrogenans 3 alpha, 20 beta-hydroxysteroid dehydrogenase and a homologous enzyme, rat dihydropteridine reductase, identifies segments and residues that are likely to be structurally important in the functioning of these enzymes especially regarding specificity for NADPH and NADH.
氨基酸序列比较显示，哺乳动物的11β-羟基类固醇脱氢酶和17β-羟基类固醇脱氢酶与细菌的3α,20β-和3β-羟基类固醇脱氢酶是同源物；也就是说，这些酶起源于一个共同的祖先。这些类固醇脱氢酶还与人类15-羟基前列腺素脱氢酶以及根瘤菌（一种在豆科植物根部形成固氮根瘤的细菌）中发现的蛋白质同源。我们构建了这些蛋白质的多序列比对，当将其与最近确定的氢化链霉菌3α,20β-羟基类固醇脱氢酶和同源酶大鼠二氢蝶啶还原酶的三级结构相结合时，可识别出在这些酶的功能中可能具有重要结构作用的片段和残基，特别是在对NADPH和NADH的特异性方面。
