Fishman J, Raju M S
J Biol Chem. 1981 May 10;256(9):4472-7.
19-Hydroxy[1 alpha-3H]androstenedione was synthesized and its specific activity was accurately determined. Upon aromatization of the above material by placental microsomal aromatase preparation, a process involving 1 beta hydrogen elimination, only 7.4% of the isotope was lost establishing the alpha orientation of the 3H at C-1 in the substrate. The 19-hydroxy[1 alpha]3H]androstenedione was used as the starting material in the synthesis of 2 beta-hydroxy-19-oxo[1 alpha-3H]androstenedione which therefore had the same specific activity and isotope orientation as its precursor. The nonenzymatic collapse of 2 beta-hydroxy-19-oxo[1 alpha-3H]androstenedione in pH 7.1 buffer to estrone was associated with the elimination of only 2.6% of the isotope indicating that this process proceeds also with stereospecific 1 beta hydrogen elimination. The stereochemistry of hydrogen loss in the nonenzymatic aromatization of the 2 beta-hydroxy-19-oxo derivative is therefore beta and identical with that of estrogen biosynthesis. This provides further evidence in support of the hypothesis that the final enzymatic hydroxylation of the aromatization sequence takes place at position 2 beta of the androgen substrate and that its product, the 2 beta-hydroxy-19-aldehyde, is the proximate precursor of estrogen with the final conversion occurring nonenzymatically.
合成了19-羟基[1α-³H]雄烯二酮并精确测定了其比活度。用胎盘微粒体芳香化酶制剂将上述物质进行芳香化反应，该过程涉及1β-氢消除，仅有7.4%的同位素损失，这确定了底物中C-1位上³H的α取向。19-羟基[1α-³H]雄烯二酮被用作合成2β-羟基-19-氧代[1α-³H]雄烯二酮的起始原料，因此其具有与其前体相同的比活度和同位素取向。2β-羟基-19-氧代[1α-³H]雄烯二酮在pH 7.1缓冲液中无酶催化转化为雌酮的过程中，仅有2.6%的同位素消除，这表明该过程也是通过立体特异性的1β-氢消除进行的。因此，2β-羟基-19-氧代衍生物无酶催化芳香化反应中氢损失的立体化学为β型，与雌激素生物合成中的相同。这为以下假说提供了进一步的证据支持：芳香化反应序列的最终酶促羟基化发生在雄激素底物的2β位，其产物2β-羟基-19-醛是雌激素的直接前体，最终转化以非酶方式发生。
