Side-chain cleavage of cholesterol sulfate by ovarian mitochondria.
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.
Tuckey
R C
RC
Department of Biochemistry, University of Western Australia, Nedlands, Perth.
D004092:20-alpha-Dihydroprogesterone / Q000031:analogs & derivatives / Q000378:metabolism; D000616:Aminoglutethimide / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D002788:Cholesterol Esters / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005260:Female; D006868:Hydrolysis; D007700:Kinetics; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity; D013552:Swine
D002788:Cholesterol Esters; D000616:Aminoglutethimide; D004092:20-alpha-Dihydroprogesterone; C052610:3-hydroxypregn-4-en-20-one; D003577:Cytochrome P-450 Enzyme System; C007045:cholesteryl sulfate