title: The intermediary role of 5-pregnene-3 ,20 -diol in the biosynthesis of 16-unsaturated C 19  steroids in boar testis.
abstract: 1. The possible involvement of 5-pregnene-3beta,20beta-diol in 16-unsaturated C(19) steroid biosynthesis has been investigated. 2. 5,16-Androstadien-3beta-ol (andien-beta) formation from [4-(14)C]pregnenolone (3beta-hydroxy-5-pregnen-20-one), 5-pregnene-3beta,20alpha-diol and 5-pregnene-3beta,20beta-diol was studied in homogenates of boar testis and the mean yields obtained were 25.6, 2.7 and 16.0% respectively. 3. Short-term kinetic studies with pregnenolone and 5-pregnene-3beta,20beta-diol separately and together suggested that the latter compound might be an intermediate in the biosynthesis of andien-beta. 4. In agreement with this interpretation, radioactive 5-pregnene-3beta,20beta-diol has been isolated during andien-beta biosynthesis from [4-(14)C]pregnenolone in the presence of NADPH, more radioactivity being trapped under limiting conditions of andien-beta formation with NADH present as cofactor. 5. Further, 5-pregnene-3beta,20beta-diol and andien-beta have been shown to inhibit the formation of the 16-unsaturated C(19) steroid from [4-(14)C]pregnenolone, the yield of radioactive 5-pregnene-3beta,20beta-diol increasing in the presence of added unlabelled andien-beta. 6. It is concluded that there may be two pathways leading to 16-unsaturated C(19) steroid formation from pregnenolone, one of these involving 5-pregnene-3beta,20beta-diol as an intermediate. Possible mechanisms are presented and discussed.
mesh_terms: D000438:Alcohols; D000736:Androstenes / Q000096:biosynthesis*; D000818:Animals; D002247:Carbon Isotopes; D055598:Chemical Phenomena; D002621:Chemistry; D003864:Depression, Chemical; D006914:Hydroxysteroids / Q000378:metabolism; D007659:Ketones; D007700:Kinetics; D008297:Male; D009249:NADP / Q000378:metabolism; D011283:Pregnenes / Q000378:metabolism*; D011284:Pregnenolone / Q000378:metabolism; D013552:Swine; D013737:Testis / Q000378:metabolism*
chemical_list: D000438:Alcohols; D000736:Androstenes; D002247:Carbon Isotopes; D006914:Hydroxysteroids; D007659:Ketones; D011283:Pregnenes; D009249:NADP; D011284:Pregnenolone