Penning T M, Sharp R B, Krieger N R
J Biol Chem. 1985 Dec 5;260(28):15266-72.
The 3 alpha-hydroxysteroid dehydrogenase (EC 1.1.1.50) of rat brain cytosol has been purified to apparent homogeneity. The purification procedure involves six successive steps, includes one affinity chromatography, and yields enzyme which displays a 1,550-fold enhancement in specific activity. The homogeneous enzyme has a Km of 8.0 microM for 5 alpha-dihydrotestosterone, a Vmax of 1.3 mumol of 3 alpha-androstanediol formed per h/mg of protein, and displays a preference for NADPH. It appears to be the major activity responsible for the reduction of 5 alpha-dihydrotestosterone in this tissue and may play a pivotal role in brain androgen metabolism. The homogeneous enzyme has several properties in common with the 3 alpha-hydroxysteroid dehydrogenase purified from rat liver cytosol (Penning, T. M., Mukharji, I., Barrows, S., and Talalay, P. (1984) Biochem. J. 222, 601-611). It is a monomer with a molecular weight of 31,000, it has a pI of 5.5, and it is potently inhibited by the nonsteroidal anti-inflammatory drugs (IC50 value for indomethacin = 2.0 microM). The potency of inhibition observed for the brain enzyme parallels that observed for cyclooxygenase: indomethacin greater than fenamates greater than l-methylpyrrole acetic acids greater than arylpropionic acids greater than salicylates greater than acetaminophen. Examination of a variety of steroidal contraceptives as modulators of the dehydrogenase indicates that ethinylestradiol is a very poor inhibitor (IC50 = 100 microM), while 6-medroxyprogesterone acetate (Provera) is an extremely potent inhibitor (IC50 = 0.2 microM). The possibility exists that brain androgen metabolism may be altered by the nonsteroidal anti-inflammatory drugs and synthetic progestins.
大鼠脑细胞质中的3α-羟基类固醇脱氢酶（EC 1.1.1.50）已被纯化至表观均一性。纯化过程包括六个连续步骤，其中包括一次亲和层析，得到的酶比活性提高了1550倍。该均一酶对5α-二氢睾酮的Km为8.0微摩尔，每小时每毫克蛋白质形成3α-雄烷二醇的Vmax为1.3微摩尔，并且对NADPH有偏好。它似乎是该组织中负责还原5α-二氢睾酮的主要活性物质，可能在脑雄激素代谢中起关键作用。该均一酶与从大鼠肝细胞质中纯化的3α-羟基类固醇脱氢酶具有若干共同特性（彭宁，T.M.，穆卡尔吉，I.，巴罗斯，S.，和塔拉莱，P.（1984年）《生物化学杂志》222卷，601 - 611页）。它是一种分子量为31000的单体，其pI为5.5，并且被非甾体抗炎药强烈抑制（吲哚美辛的IC50值 = 2.0微摩尔）。观察到的脑酶抑制效力与环氧化酶的抑制效力相似：吲哚美辛＞芬那酸盐＞1 - 甲基吡咯乙酸＞芳基丙酸＞水杨酸盐＞对乙酰氨基酚。对多种甾体避孕药作为脱氢酶调节剂的研究表明，乙炔雌二醇是一种非常弱的抑制剂（IC50 = 100微摩尔），而醋酸6 - 甲羟孕酮（安宫黄体酮）是一种极其有效的抑制剂（IC50 = 0.2微摩尔）。非甾体抗炎药和合成孕激素可能会改变脑雄激素代谢。
