Kohara H, Shimizu K
Biochim Biophys Acta. 1987 Sep 4;921(1):90-5.
[16 alpha-2H]Pregnenolone was synthesized by catalytic deuteriation of 3 beta-hydroxy-5,16-pregnadien-20-one followed by base-catalyzed back exchange of the 17 alpha-2H atom, and [16 beta-2H]pregnenolone by catalytic hydrogenation of 3 beta-hydroxy-5,16-[16-2H]pregnadien-20-one, which had been synthesized from [16,16-2H]dehydroepiandrosterone. The labelled pregnenolones were incubated separately with the microsomal fraction of boar testis. The metabolites were analyzed by gas chromatography-mass spectrometry, and the isotope compositions of the following six metabolites were determined: 17-hydroxypregnenolone, dehydroepiandrosterone, 5-androstene-3 beta,17 alpha-diol, 5-androstene-3 beta,17 beta-diol,16 alpha-hydroxypregnenolone and 5,16-androstadien-3 beta-ol. The first four metabolites derived either from [16 alpha-2H]- or from [16 beta-2H]pregnenolone showed essentially the same isotope compositions as those of their respective precursors. The 16 alpha-hydroxypregnenolone and the 5,16-androstadien-3 beta-ol biosynthesized from [16 alpha-2H]pregnenolone lost the 2H label, while the same metabolites biosynthesized from [16 beta-2H]pregnenolone retained the albel. The result shows that the 16 alpha-hydrogen is stereospecifically removed with the retention of the 16 beta-hydrogen in the biosynthesis of 5,16-androstadien-3 beta-ol.
[16α-2H]孕烯醇酮是通过对3β-羟基-5,16-孕二烯-20-酮进行催化氘化，然后对17α-2H原子进行碱催化反向交换而合成的；[16β-2H]孕烯醇酮则是通过对由[16,16-2H]脱氢表雄酮合成的3β-羟基-5,16-[16-2H]孕二烯-20-酮进行催化氢化而合成的。将标记的孕烯醇酮分别与公猪睾丸的微粒体部分一起温育。通过气相色谱-质谱联用仪分析代谢产物，并测定了以下六种代谢产物的同位素组成：17-羟基孕烯醇酮、脱氢表雄酮、5-雄烯-3β,17α-二醇、5-雄烯-3β,17β-二醇、16α-羟基孕烯醇酮和5,16-雄二烯-3β-醇。由[16α-2H]-或[16β-2H]孕烯醇酮衍生的前四种代谢产物的同位素组成与其各自前体的同位素组成基本相同。由[16α-2H]孕烯醇酮生物合成的16α-羟基孕烯醇酮和5,16-雄二烯-3β-醇失去了2H标记，而由[16β-2H]孕烯醇酮生物合成的相同代谢产物则保留了标记。结果表明，在5,16-雄二烯-3β-醇的生物合成中，16α-氢被立体特异性去除，同时保留了16β-氢。
