pThe activity of 3β-hydroxy steroid dehydrogenase (EC 1.1.1.51) in the mitochondrial fraction of rat adrenal homogenates was approx. 31% of the total activity recovered after differential centrifugation and washing of the particulate fractions. Some 45% of the total activity was found in the microsomal fraction. The activity was assayed by a radioisotopic method devised in this laboratory for the purpose of studying small quantities of tissue and cell fractions. Satisfactory separation of the two fractions was demonstrated by electron microscopy of the pellets and by comparative recoveries of RNA, steroid 21-hydroxylase and cytochrome ic/i oxidase in the various compartments. Analyses of the kinetics of the enzyme activity in the two fractions revealed no significant differences in apparent iKsubm/sub/i for pregnenolone, dehydroepiandrosterone or NADsup+/sup, but demonstrated a distinct difference in the iKsubm/sub/i for NADPsup+/sup. pH optima and susceptibility to cyanoketone inhibition were similar in both fractions./p
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机译：>大鼠肾上腺匀浆线粒体部分中的3β-羟基类固醇脱氢酶（EC 1.1.1.51）的活性约为。在离心分离和洗涤颗粒部分后，回收了总活性的31％。在微粒体部分中发现了总活性的约45％。通过在该实验室中设计用于研究少量组织和细胞级分的放射性同位素方法来测定活性。通过沉淀的电子显微镜检查和在各个区室中对RNA，类固醇21-羟化酶和细胞色素 c 氧化酶的比较回收率证实了两个部分的满意分离。对这两个部分的酶活性动力学分析表明，孕烯醇酮，脱氢表雄酮或NAD + 的表观 K m 没有显着差异，但证明了NADP + 的 K m 明显不同。两个部分的最佳pH值和对氰基酮抑制的敏感性相似。
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