Guller S, Gravanis A, Gurpide E
J Steroid Biochem. 1986 May;24(5):935-44. doi: 10.1016/0022-4731(86)90344-4.
17 beta-Hydroxysteroid oxidoreductase, as well as estrone sulfate and dehydroepiandrosterone sulfate sulfatases, were found in the plasma membrane of microvilli of the fetal syncytiotrophoblast. Because of their location, these enzymes may influence feto-maternal transfer of steroids circulating as sulfates, the utilization of sulfated estrogen precursors and the proportion of estrone and estradiol delivered towards fetal and maternal circulations. Microvillar vesicles isolated from human term placentas were disrupted in hypotonic medium to obtain a membrane preparation. A fraction of the estradiol 17 beta-oxidoreductase (E2DH) activity in the vesicle remained associated to the membrane after disruption and treatment with 2 M NaCl. The membrane-associated activity was resistant to inhibition with trypsin and did not react with a polyclonal antibody which neutralized cytosolic E2DH activity. The membrane-associated enzyme was solubilized with a cholate-glycerol buffer solution and purified on Sephadex G-100. The estimated molecular weight of the solubilized enzyme (137 kDa) appears to correspond to a tetramer since it was found to be about twice the size of the cytosolic enzyme. Both enzymes focused in polyacrylamide gels at pH 5.2. The Km relative to E2 of the membrane-associated E2DH (1.3 microM) differs from those of mitochondrial (0.43 microM), microsomal (0.69 microM) and cytosolic (11 microM) fractions. The cytosolic and the microvillar membrane associated 17 beta-hydroxysteroid oxidoreductases also differ in their specificity for C18 and C19 steroid substrates and in their pH dependence patterns. Sulfatases acting on estrone sulfate and dehydroepiandrosterone sulfate in microvillar membranes were insensitive to trypsin and as resistant to washes with 2 M NaCl as alkaline phosphatase. This data indicated that steroid sulfatases are also microvillar membrane associated enzymes of potential physiologic importance in the hydrolysis of estrogen precursors.
在胎儿合体滋养层微绒毛的质膜中发现了17β-羟类固醇氧化还原酶以及硫酸雌酮和硫酸脱氢表雄酮硫酸酯酶。由于它们的位置，这些酶可能会影响以硫酸盐形式循环的类固醇的母婴转运、硫酸化雌激素前体的利用以及向胎儿和母体循环输送的雌酮和雌二醇的比例。从足月人胎盘分离的微绒毛小泡在低渗介质中破裂以获得膜制剂。小泡中的一部分雌二醇17β-氧化还原酶（E2DH）活性在破裂并用2M NaCl处理后仍与膜相关。膜相关活性对胰蛋白酶抑制有抗性，并且不与中和胞质E2DH活性的多克隆抗体反应。膜相关酶用胆酸盐-甘油缓冲溶液溶解并在Sephadex G-100上纯化。溶解酶的估计分子量（137 kDa）似乎对应于四聚体，因为发现它大约是胞质酶大小的两倍。两种酶在pH 5.2的聚丙烯酰胺凝胶中聚焦。膜相关E2DH相对于E2的Km（1.3 microM）与线粒体（0.43 microM）、微粒体（0.69 microM）和胞质（11 microM）部分的Km不同。胞质和微绒毛膜相关的17β-羟类固醇氧化还原酶在对C18和C19类固醇底物的特异性以及它们的pH依赖性模式方面也有所不同。作用于微绒毛膜中硫酸雌酮和硫酸脱氢表雄酮硫酸酯的硫酸酯酶对胰蛋白酶不敏感，并且与碱性磷酸酶一样耐受2M NaCl洗涤。该数据表明类固醇硫酸酯酶也是微绒毛膜相关酶，在雌激素前体的水解中具有潜在的生理重要性。
