Adrenal gland steroid C-21 cytochrome P-450 reductase

Abstract

The adrenal gland mitochondrial cytochrome P-450 reductase system (adrenal flavoprotein and adrenodoxin) is shown in this investigation to enhance steroid 21 hydroxylation in carefully prepared microsomal suspensions and acetone powder extracts. Examination of the reductase components separately reveals that the enhancement can be accounted for on the basis of the flavoprotein moiety alone.This implicates flavoprotein as an electron carrier in steroid 21 hydroxylation. While it seems likely that the mitochondrial and microsomal flavoproteins are identical, there remains a possibility that different, yet compatible, species may exist for the two organelles. The current studies indicate that V^/teroid 11/3 hydroxylation was early shown to occur in adrenal gland cortex mitochondria (Sweat, 1951) and to require TPNH (Sweat and Lipscomb, 1955; Grant and Brownie, 1955) and molecular oxygen (Sweat et al., , 1956 Hayano et al., 1955a,b) as participants in the reaction. Shortly thereafter, 21 hydroxylation was shown to be associated with elements of the adrenal gland cortex endoplasmic reticulum (Plager and Samuels, 1954) and to also require TPNH (Ryan and Engel, 1956) and molecular oxygen (Cooper et al., 1963;Nakano et al., 1968). Both 11/3-and 21-hydroxylation reactions have been classified in the category of mixedfunction oxidases (Mason, 1957). While it has been suggested that steroid hydroxylations may occur as a generalized process, Mason (1957) has pointed out that nonspecific reactions characteristic of free radicals are not apparent in the steroid

Purification and properties of chick renal mitochondrial ferredoxin

“…The adrenocortical mitochondrial ferredoxin was first reported by Omura et al (1965) and Kimura & Suzuki (1965), who proposed that this iron-sulfur protein component and an FAD-containing flavoprotein constituted an NADPH-dependent cytochrome P-450 reductase complex active in the 11/3-hydroxylation of deoxycorticosterone. Both adrenodoxin2 and adrenodoxin reductase have since been well characterized (Kimura & Suzuki, 1967;Suhara et al, 1972;Nakamura & Otsuka, 1966;Sweat et al, 1969).…”

Adrenodoxin, Ferredoxins and Other Iron-Sulphur (Nonheme-Iron) Proteins

“…It is, however, generally accepted that a protein containing nonheme-iron and acid-labile sulphur does not participate in the hepatic microsomal hydroxylations of steroids and other substrates and indeed such proteins are probably absent in the liver [see 136]. A similar situation is believed to occur in adrenocortical microsomal steroid hydroxylations [178,281,312]. Adrenodoxin-like proteins are thought, however, to participate in steroidogenic hydroxylations by the mitochondria of the placenta, testis and corpus luteum of the ovary [136,176,278], It has been confirmed that the testis and corpus luteum ISPs can substitute for adrenodoxin in a deoxy corticosterone 11 ß-hydroxylating activity assay while corresponding prepara tions from liver, and Euglena and spinach ferredoxins, Pseudomonas rubredoxin and Pseudomonas putidaredoxin are inactive [136].…”

Purification and optical studies of cytochrome P‐450 from bovine adrenocortical microsomes

“…Recently, two different kinds ofmitochondrialP-450 cytochromes, catalyzing the cholesterol side-chain cleavage (P-450scc) and the steroid 11/3-hydroxylation (P-4501U3) have been highly purified from bovine adrenal cortex [1][2][3]. Investigations on the reaction mechanism of cytochrome P-450 in adrenal endoplasmic reticulum have been carried out using a microsomal particle or its extract [4][5][6][7][8][9][10][11][12][13]. However, so far as we know, no isolation of cytochrome P-450 from the microsomes has been achieved.…”