Adams J B, Martyn P, Smith D L, Nott S
School of Biochemistry, University of New South Wales, Sydney, Australia.
Steroids. 1988 Mar-Apr;51(3-4):251-67. doi: 10.1016/0039-128x(88)90017-7.
Microsomal preparations derived from bovine placenta cotyledons, previously investigated as a convenient source of fatty acyl coenzyme A: estradiol-17 beta-acyl transferase, have been shown to acylate other steroids bearing 3 beta- or 17 beta-hydroxyl groups. In the presence of 0.1 mM oleoyl CoA, the apparent Km values for dehydroepiandrosterone, testosterone, and 5-androstene-3 beta,17 beta-diol (delta 5-DIOL) were 45, 67, and 20 microM, respectively. Acylation of delta 5-DIOL occurred at either the 3 beta- or 17 beta-positions to give monoesters. Testosterone, estradiol-17 beta, and delta 5-DIOL acted as competitive inhibitors for the acylation of the 3 beta-hydroxyl group of dehydroepiandrosterone (Ki values 71, 75, and 41 microM, respectively). Such data indicate that a single enzyme of wide substrate specificity may be involved in these acylation reactions. When estrogen receptor (ER) positive and negative human mammary cancer cell lines were incubated with 10 nM [3H]delta 5-DIOL, intracellular accumulation of delta 5-DIOL long-chain fatty acid esters occurred; rates being higher (p less than 0.001) in ER negative cells (MDA-MB-231 and MDA-MB-330) compared to MCF-7 cells (ER positive), and higher (P less than 0.005) in MDA-MB-231 cells compared to ZR-75-1 cells (ER positive). After exposure to 10 nM [3H]delta 5-DIOL for 16 h, the total labeled steroid fatty acid fraction was composed predominantly of delta 5-DIOL-3 beta- and 17 beta-monoesters (approximately 85%), the remainder containing approximately equal amounts of delta 5-DIOL-diesters and dehydroepiandrosterone-3 beta-esters. Subsequent transfer to medium lacking delta 5-DIOL was accompanied by a breakdown of the labeled esters, which was more rapid in the ER positive cell lines. During this period, intracellular free delta 5-DIOL levels rapidly declined in MDA-MB-330 cells but were maintained in MCF-7 cells, presumably by binding to ER. This behavior parallels that of estradiol-17 beta previously observed in these cell lines and further emphasizes the potential importance of the adrenal-derived estrogen delta 5-DIOL in consideration of a hormone-based etiology of human breast cancer.
源自牛胎盘子叶的微粒体制剂，之前被作为脂肪酰基辅酶A：雌二醇-17β-酰基转移酶的便捷来源进行研究，现已表明其可使其他带有3β-或17β-羟基的类固醇发生酰化反应。在0.1 mM油酰辅酶A存在的情况下，脱氢表雄酮、睾酮和5-雄烯-3β,17β-二醇（δ5-DIOL）的表观Km值分别为45、67和20 μM。δ5-DIOL在3β-或17β-位发生酰化反应生成单酯。睾酮、雌二醇-17β和δ5-DIOL对脱氢表雄酮3β-羟基的酰化反应起竞争性抑制作用（Ki值分别为71、75和41 μM）。这些数据表明，这些酰化反应可能涉及一种具有广泛底物特异性的单一酶。当雌激素受体（ER）阳性和阴性的人乳腺癌细胞系与10 nM [3H]δ5-DIOL一起孵育时，δ5-DIOL长链脂肪酸酯在细胞内积累；与MCF-7细胞（ER阳性）相比，ER阴性细胞（MDA-MB-231和MDA-MB-330）中的积累速率更高（p < 0.001），与ZR-75-1细胞（ER阳性）相比，MDA-MB-231细胞中的积累速率更高（P < 0.005）。在暴露于10 nM [3H]δ5-DIOL 16小时后，总的标记类固醇脂肪酸部分主要由δ5-DIOL-3β-和17β-单酯组成（约85%），其余部分含有大致等量的δ5-DIOL-二酯和脱氢表雄酮-3β-酯。随后转移至缺乏δ5-DIOL的培养基中伴随着标记酯的分解，这在ER阳性细胞系中更快。在此期间，MDA-MB-330细胞内游离δ5-DIOL水平迅速下降，但在MCF-7细胞中保持稳定，推测是通过与ER结合。这种行为与之前在这些细胞系中观察到的雌二醇-17β的行为相似，并进一步强调了肾上腺衍生的雌激素δ5-DIOL在考虑人类乳腺癌基于激素的病因学方面的潜在重要性。
