Inhibitory Effects of 20α-Hydroxyprogesterone on Steroid Hydroxylation Reactions of Guinea Pig Adrenal Microsomes  

作　　者：黄德盈 Shiro Kominami Shigeki Takemori 

机构地区：[1]Department of Chemistry, South Central Institute for National Minorities, Wuhan 430074, PRC [2]Faculty of Integrated Arts and Sciences, Hiroshima University

出　　处：《Science China Chemistry》1993年第4期411-419,共9页中国科学（化学英文版）

摘　　要：Using guinea pig andrenal microsomes, we studied the inhibitory effects of 20α-hydroxyprogesterone on steroid hydroxylation reactions catalyzed by cytochromes P-450. When 17α-hydroxyprogesterone was used as a substrate, 20α-hydroxyprogesterone functioned as a competitive inhibitor on the C_(17)—C_(20) bond cleavage reaction of P-450_(17α lyase). The inhibition constant, K_i was 1.37 μmol/L. 20α-hydroxyprogesterone also competitively inhibited the convertion of 17α-bydroxyprogesterone to 11-deoxycortisol by the action of P-450_(c21). The value of K_i was 1.73μmol/L. When progesterone was used as a substrate, 20α-hydroxyprogesterone inhibited neither the 21-hydroxylation of P-450_(c21). the C_(17)—C_(20) bond cleavage, nor 17α-hydroxylation of P-450_(17α lyase). Based on the seresults, we can deduce that the production of androstenedione from progesterone by the action of P-450_(17α lyase) proceeds through a successive monooxygenase reaction.Using guinea pig andrenal microsomes, we studied the inhibitory effects of 20α-hydroxyprogesterone on steroid hydroxylation reactions catalyzed by cytochromes P-450. When 17α-hydroxyprogesterone was used as a substrate, 20α-hydroxyprogesterone functioned as a competitive inhibitor on the C₁₇—C₂₀ bond cleavage reaction of P-450_{17α lyase}. The inhibition constant, K_i was 1.37 μmol/L. 20α-hydroxyprogesterone also competitively inhibited the convertion of 17α-bydroxyprogesterone to 11-deoxycortisol by the action of P-450_c21. The value of K_i was 1.73μmol/L. When progesterone was used as a substrate, 20α-hydroxyprogesterone inhibited neither the 21-hydroxylation of P-450_c21. the C₁₇—C₂₀ bond cleavage, nor 17α-hydroxylation of P-450_{17α lyase}. Based on the seresults, we can deduce that the production of androstenedione from progesterone by the action of P-450_{17α lyase} proceeds through a successive monooxygenase reaction.

关 键 词：cytochrome P-450_(c21) cytochrome P-450_(17α lyase ) 20α-hydroxyprogesterone adrenal microsome steroidogenesis. 

分 类 号：O6[理学—化学]