Conversion of 5 alpha-pregnane-3,20-dione, 3 alpha-hydroxy-5 alpha-pregnan-20-one and 3 beta-hydroxy-5 alpha-pregnan-20-one to delta 16-C19 steroids by the reconstituted delta 16-C19-steroid synthetase system.
The substrate specificity of the reconstituted delta 16-C19-steroid synthetase system, which catalyzes the formation of 5,16-androstadien-3 beta-ol or 4,16-androstadien-3-one from pregnenolone or progesterone, respectively, was studied. The reconstituted system consisted of a partially purified cytochrome P-450, NADPH-cytochrome P-450 reductase, cytochrome b5 and NADH-cytochrome b5 reductase all from pig testicular microsomes. It was found that 5 alpha-reduced C21 steroids such as 5 alpha-pregnane-3,20-dione, 3 alpha-hydroxy-5 alpha-pregnan-20-one and 3 beta-hydroxy-5 alpha-pregnan-20-one can be substrates for the enzyme system, resulting in the formation of 5 alpha-androst-16-en-3-one, 5 alpha-androst-16-en-3 alpha-ol and 5 alpha-androst-16-en-3 beta-ol, respectively. The results suggest that 5 alpha-reduced delta 16-C19 steroids might be synthesized from pregnenolone and progesterone via 5 alpha-reduced C21 steroids as intermediates. The pathways would bypass 5,16-androstadien-3 beta-ol and 4,16-androstadien-3-one which have been assumed as obligatory intermediates in the formation of 5 alpha-reduced delta 16-C19 steroids from pregnenolone and progesterone.
Kohara
H
H
Division of Biochemistry, Tottori University School of Medicine, Yonago, Japan.
Shimizu
K
K
Yamaga
N
N
D043582:5-alpha-Dihydroprogesterone; D000730:Androstadienes / Q000096:biosynthesis*; D000818:Animals; D008297:Male; D008861:Microsomes / Q000201:enzymology; D010088:Oxidoreductases / Q000378:metabolism*; D011277:Pregnanediones / Q000378:metabolism*; D011278:Pregnanes / Q000378:metabolism*; D011280:Pregnanolone / Q000378:metabolism*; D011284:Pregnenolone / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism; D013256:Steroids / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine; D013737:Testis / Q000201:enzymology
D000730:Androstadienes; D011277:Pregnanediones; D011278:Pregnanes; D013256:Steroids; C003524:4,16-androstadien-3-one; D011374:Progesterone; D011284:Pregnenolone; D043582:5-alpha-Dihydroprogesterone; D011280:Pregnanolone; D010088:Oxidoreductases; C019701:androsta-5,16-dien-3 beta-ol synthetase; D013254:Steroid 17-alpha-Hydroxylase