Tuckey R C
Department of Biochemistry, University of Western Australia, Nedlands, Perth.
J Steroid Biochem Mol Biol. 1990 Sep;37(1):121-7. doi: 10.1016/0960-0760(90)90380-4.
Mitochondria isolated from porcine corpora lutea and from the luteinized ovaries of gonadotropin-treated immature rats were found to efficiently cleave the side-chain of cholesterol sulfate to produce 3 beta-hydroxy-5-pregnen-20-one sulfate (pregnenolone sulfate). When mitochondria were preincubated with cholesterol sulfate, the time-course for the side-chain cleavage of cholesterol sulfate was biphasic. With 200 microM cholesterol sulphate, the initial rate of the reaction was the same as that observed for 25-hydroxycholesterol. This rate was not increased when both cholesterol sulfate and 25-hydroxycholesterol were incubated together. The rate of side-chain cleavage by isolated mitochondria supplied with 75 microM cholesterol sulfate as substrate was inhibited by 97% by aminoglutethimide, a specific inhibitor of cytochrome P-450scc. The slow phase of side-chain cleavage of cholesterol sulfate appeared to be limited by the rate of substrate movement to the mitochondrial site of the reaction. Cholesterol sulfate translocation rates were however up to 8 times greater than those observed for cholesterol when equivalent concentrations of the two substrates were added to the mitochondria. We conclude that cholesterol sulfate is a better substrate than cholesterol for side-chain cleavage by isolated mitochondria and that both reactions are catalysed by the same cytochrome P-450scc enzyme.
从猪黄体以及促性腺激素处理的未成熟大鼠的黄体化卵巢中分离出的线粒体，被发现能够有效地裂解硫酸胆固醇的侧链，生成3β-羟基-5-孕烯-20-酮硫酸盐（硫酸孕烯醇酮）。当线粒体与硫酸胆固醇预孵育时，硫酸胆固醇侧链裂解的时间进程呈双相。对于200微摩尔硫酸胆固醇，反应的初始速率与观察到的25-羟基胆固醇的初始速率相同。当硫酸胆固醇和25-羟基胆固醇一起孵育时，该速率并未增加。以75微摩尔硫酸胆固醇作为底物，分离出的线粒体进行侧链裂解的速率被细胞色素P-450scc的特异性抑制剂氨鲁米特抑制了97%。硫酸胆固醇侧链裂解的慢相似乎受底物向线粒体反应位点移动速率的限制。然而，当向线粒体中加入等量浓度的两种底物时，硫酸胆固醇的转运速率比胆固醇的转运速率高8倍。我们得出结论，对于分离出的线粒体进行侧链裂解而言，硫酸胆固醇是比胆固醇更好的底物，并且这两种反应均由同一种细胞色素P-450scc酶催化。
