Steroidogenesis in liposomal system containing adrenal microsomal cytochrome P-450 electron transfer components.
Purified adrenal microsomal P-450C21 and/or P-45017 alpha,lyase were incorporated with purified NADPH-cytochrome-P-450 reductase into liposome membranes composed of phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine at a molar ratio of 5:3:1. The rate dependences of reduction of liposomal P-450C21 in the fast phase as well as progesterone hydroxylation activities of P-450C21 and P-45017 alpha,lyase on the reductase concentration in the liposome membranes suggested that electrons were delivered through random collisions between the reductase and cytochrome P-450s in the liposome membranes. A rapid exchange of the steroid metabolic intermediate between vesicles was observed in a reaction system consisting of P-450C21-proteoliposomes and P-45017 alpha,lyase-proteoliposomes. Using the combined liposomal system, it was definitely proved that androstenedione was formed from progesterone mainly by a successive hydroxylation reaction without the intermediate 17 alpha-hydroxyprogesterone leaving from P-45017 alpha,lyase. It was also found that 21-hydroxylation of 17 alpha-hydroxyprogesterone into 11-deoxycortisol was inhibited by a physiological concentration of progesterone.
Kominami
S
S
Faculty of Integrated Arts and Sciences, Hiroshima University, Japan.
Inoue
S
S
Higuchi
A
A
Takemori
S
S
D000311:Adrenal Glands / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004579:Electron Transport; D008081:Liposomes / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology*; D010084:Oxidation-Reduction; D013256:Steroids / Q000096:biosynthesis* / Q000378:metabolism
D008081:Liposomes; D013256:Steroids; D003577:Cytochrome P-450 Enzyme System