Cytochrome P-450 and 18-oxygenase system from beef adrenocortical mitochondria. — Spectral and kinetic studies

Abstract

Summary The transformation of corticosterone to aldosterone and the binding of corticosterone to cytochrome P-450 were studied in beef adrenal mitochondria. The corticosterone concentration giving a half maximal rate of aldosterone synthesis was found to be 1.510 −5 M in beef adrenal mitochondrial preparations. 7.010 −5 M was the concentration at which half maximal binding of corticosterone to cytochrome P-450 was obtained. pH 7.0 was found optimal for both the binding of corticosterone to cytochrome P-450 and its transformation to aldosterone. 2M urea diminished the binding of corticosterone to cytochrome P-450 by 78% and the conversion of corticosterone to aldosterone by 72%. It seem that in vitro factors favouring the binding of corticosterone to cytochrome P-450 also favour the transformation of corticosterone to aldosterone.