Hales D B, Betz G
J Steroid Biochem. 1984 Dec;21(6):639-42. doi: 10.1016/0022-4731(84)90024-4.
The cytochrome P-450 of gonadal microsomes is an integral component of the steroid converting enzymes, 17 alpha-hydroxylase and 17,20-lyase. Interaction of the steroid substrates with this cytochrome results in a shift in the Soret band as measured by difference spectroscopy. In these studies it is shown that in contrast to placental microsomal cytochrome P-450 which binds C19 steroids, testis microsomal cytochrome P-450 primarily binds C21 steroids. However, addition of a 17 alpha- methyl, 17 beta-acetate or a 17 beta-benzoate group to testosterone permits interaction. The addition of hydroxyl or methyl groups to other positions does not affect binding. The presence of multiple oxygen functions on C21 steroids, as in cortisol and corticosterone, precludes interaction. At least one oxygen function seems necessary for binding as 5 alpha- and 5 beta-pregnane do not bind whereas 20-deoxypregnenolone (5-pregnen-3 beta-ol) does bind. These findings indicate that factors in addition to hydrophobic interactions dictate the binding of steroid substrates to testis microsomal cytochrome P-450.
性腺微粒体中的细胞色素P-450是类固醇转化酶17α-羟化酶和17,20-裂解酶的一个组成部分。类固醇底物与这种细胞色素的相互作用会导致通过差示光谱法测量的Soret带发生位移。在这些研究中表明，与结合C19类固醇的胎盘微粒体细胞色素P-450不同，睾丸微粒体细胞色素P-450主要结合C21类固醇。然而，在睾酮上添加17α-甲基、17β-乙酸酯或17β-苯甲酸酯基团可允许相互作用。在其他位置添加羟基或甲基不会影响结合。C21类固醇上存在多个氧官能团，如皮质醇和皮质酮中的情况，会排除相互作用。至少一个氧官能团似乎是结合所必需的，因为5α-和5β-孕烷不结合，而20-脱氧孕烯醇酮（5-孕烯-3β-醇）确实结合。这些发现表明，除了疏水相互作用外，还有其他因素决定类固醇底物与睾丸微粒体细胞色素P-450的结合。
