MECHANISTIC STUDIES ON C-19 DEMETHYLATION IN ESTROGEN BIOSYNTHESIS
MECHANISTIC STUDIES ON C-19 DEMETHYLATION IN ESTROGEN BIOSYNTHESIS
复制标题
DOI：
10.1042/bj2010569
复制
发表时间：
1982-01-01
影响因子：
4.1
通讯作者：
WRIGHT, JN
中科院分区：
文献类型：
--
作者：
AKHTAR, M;CALDER, MR;WRIGHT, JN
利用足月人胎盘的微粒体制剂研究了雌激素生物合成的机制。整个转化过程称为芳构化过程，涉及使用 O2 和 NADPH 的 3 个步骤，其中雄激素的 C-19 甲基被氧化为甲酸，同时生成雌激素的芳环：.**图形**。为了研究氧原子参与这一过程的机制，合成了许多标记的前体。其中值得注意的是 19-羟基-4-雄烯-3,17-二酮 (II) 和 19-氧代-4-雄烯-3,17-二酮 (IV)，其中 C-19 除了 18O 之外还用 2H 标记。为了追踪芳构化过程中 (II) 和 (IV) 的 C-19 处标记原子的命运，将 C-19 释放的甲酸进行苄基化并通过质谱法进行分析。设计实验程序以尽量减少底物和产物中的 O2 原子与介质中的氧的交换。在类型(II)和(IV)的19-[18O]化合物转化为3-羟基-1,3,5-(10)-雌三烯-17-酮(V，雌酮)时，来自C-19的甲酸保留了原始底物氧。当等量的 16O 底物在 18O2 下芳构化时，两种底物中的甲酸均含有 1 个 18O 原子。有人认为，在19-羟基化合物(II)转化为19-氧代化合物(IV)的过程中，前者的C-19氧保持完整，并且在19-氧代化合物(IV)转化为雌激素的过程中，来自O2的1个氧原子并入甲酸中。通过证明在4-雄烯-3,17-二酮(I)的芳构化过程中，甲酸中的两个氧原子均源自分子氧，进一步证实了这一结论。合成了芳构化中可能的中间体10.β-羟基-4-雌烯-3,17-二酮甲酸酯，并且显示其不会转化为雌激素。根据迄今为止积累的证据，讨论了19-羟基化合物(II)转化为19-氧代化合物(IV)的立体化学方面，以及19-氧代化合物(IV)转化为雌激素期间C-10.sbd.C-19键断裂步骤的机制特征。
Mechanistic aspects of the biosynthesis estrogen were studied with a microsomal preparation from full-term human placenta. The overall transformation, termed the aromatization process, involves 3 steps using O2 and NADPH, in which the C-19 methyl group of an androgen is oxidized to formic acid with concomitant production of the aromatic ring of estrogen: .**GRAPHIC**. To study the mechanism of this process in terms of the involvement of the oxygen atoms, a number of labeled precursors were synthesized. Notable among these were 19-hydroxy-4-androstene-3,17-dione (II) and 19-oxo-4-androstene-3,17-dione (IV) in which the C-19 was labeled with 2H in addition to 18O. In order to follow the fate of the labeled atoms at C-19 of (II) and (IV) during the aromatization, the formic acid released from C-19 was benzylated and analyzed by mass spectrometry. Experimental procedures were devised to minimize the exchange of O2 atoms in substrates and product with oxygens of the medium. In the conversion of the 19-[18O] compounds of types (II) and (IV) into 3-hydroxy-1,3,5-(10)-estratriene-17-one (V, estrone), the formic acid from C-19 retained the original substrate oxygen. When the equivalent 16O substrates were aromatized under 18O2, the formic acid from both substrates contained 1 atom of 18O. It is argued that in the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), the C-19 oxygen of the former remains intact and that 1 atom of oxygen from O2 is incorporated into formic acid during the conversion of the 19-oxo compound (IV) into estrogen. This conclusion was further substantiated by demonstrating that, in the aromatization of 4-androstene-3,17-dione (I), both the oxygen atoms in the formic acid originated from molecular oxygen. 10.beta.-Hydroxy-4-estrene-3,17-dione formate, a possible intermediate in the aromatization, was synthesized and shown not to be converted into estrogen. In the light of the cumulative evidence available to date, stereochemical aspects of the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), and mechanistic features of the C-10.sbd.C-19 bond cleavage step during the conversion of the 19-oxo compound (IV) into estrogen are discussed.