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Membranes des mitochondries de cortex surrénal de boeuf. Isolement, purification et propriétés enzymatiques générales. Réactivité vis-à-vis de la désoxycorticostérone.

Abstract : Adrenal cortex mitochondria contain a cytochrome P-450 involved in the mitochondrial steroid 11beta-hydroxylation and similar to the cytochrome P-450 found in the microsomes. The outer and inner membranes from adrenal cortex mitochondria were separated following centrifugation on a sucrose density gradient and differentiated on the basis of their morphology and of their enzyme distribution pattern. The enzymatic system concerned with the 11beta-hydroxylation is strictly confined to the inner membrane fraction. The absence of cytochrome P-450 from the outer membrane is a significant difference between the outer mitochondrial membrane and the microsomal membranes in adrenal cortex. The use of ferricyanide as a nonpenetrating electron acceptor has shown that the cytochrome P-450 involved in the 11beta-hydroxylation of deoxyorticosterone is located on the matrix side of the inner mitochondrial membrane.
The binding of deoxycorticosterone and metyrapol, an inhibitor of steroid hydroxylation, to adrenal cortex mitochondria has been investigated. High-affinity binding sites (N = 0.5 nmol/mg of protein and Kd = 7.5 x 10-9 M) for metyrapol have only been found in the inner mitochondrial membrane in agreement with the localization of the mitochondrial cytochrome P-450 in the same membrane. The number of metyrapol binding sites in mitochondria is similar to the number of high-affinity sites found for steroids which are substrates of the 11beta-hydroxylase system. This number is about half the amount of mitochondrial cytochrome P-450 (1.1 nmol/mg of protein) supporting the occurence of two types of cytochrome P-450 in adrenal cortex mitochondria, one specific for the 11beta-hydroxlation, and another for the cholesterol side-chain cleavage.
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https://tel.archives-ouvertes.fr/tel-00216050
Contributor : Michel Satre <>
Submitted on : Thursday, January 24, 2008 - 12:59:47 PM
Last modification on : Friday, November 6, 2020 - 4:14:40 AM
Long-term archiving on: : Thursday, April 15, 2010 - 2:43:26 AM

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Michel Satre. Membranes des mitochondries de cortex surrénal de boeuf. Isolement, purification et propriétés enzymatiques générales. Réactivité vis-à-vis de la désoxycorticostérone.. Sciences du Vivant [q-bio]. Université Joseph-Fourier - Grenoble I, 1973. Français. ⟨tel-00216050⟩

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