Martini R, Murray M
Department of Medicine, University of Sydney, Westmead Hospital, NSW, Australia.
J Steroid Biochem Mol Biol. 1993 Jun;45(6):581-4. doi: 10.1016/0960-0760(93)90175-v.
Androst-4-ene-3,17-dione (androstenedione) was found to be a potent competitive inhibitor of the NADH-supported reduction of retinal in rat hepatic microsomes (Ki 42 microM, Km/Ki ratio 1.1). Similarly, the NADH-mediated reduction of androstenedione was inhibited in mixed fashion by retinal (Ki 12 microM, Km/Ki ratio 0.34). In subsequent experiments the cofactor NADH exhibited an identical Km (8 microM) in the microsomal reductions of both substrates. Acidic pH markedly stimulated the microsomal reduction of androstenedione to testosterone and was also found to enhance retinal reduction to retinol, although the latter reaction exhibited a distinct pH optimum between 6.0 and 6.5. These results suggest that a common enzyme may participate in the reduction of both substrates but at least one other enzyme probably participates in hepatic microsomal testosterone production.
雄甾-4-烯-3,17-二酮（雄烯二酮）被发现是大鼠肝微粒体中NADH支持的视黄醛还原反应的一种强效竞争性抑制剂（Ki为42微摩尔，Km/Ki比值为1.1）。同样，视黄醛以混合方式抑制NADH介导的雄烯二酮还原反应（Ki为12微摩尔，Km/Ki比值为0.34）。在后续实验中，辅因子NADH在两种底物的微粒体还原反应中表现出相同的Km（8微摩尔）。酸性pH显著刺激雄烯二酮微粒体还原为睾酮，并且还发现其增强视黄醛还原为视黄醇，尽管后一反应在6.0至6.5之间呈现出明显的最适pH。这些结果表明，一种共同的酶可能参与两种底物的还原，但至少另一种酶可能参与肝微粒体睾酮的生成。
