Isolation from adrenal cortex of a nonheme iron protein and a flavoprotein functional as a reduced triphosphopyridine nucleotide-cytochrome P-450 reductase

Congenital lipoid adrenal hyperplasia: the human gene knockout for the steroidogenic acute regulatory protein

“…Koizumi et al (1977) also found that affected mitochondria failed to convert cholesterol to pregnenolone but were unable to account for Degenhart's findings. By this time it was clear that the conversion of cholesterol to pregnenolone was catalyzed by a mitochondrial cytochrome P450 enzyme, termed P450scc, (where scc denotes side chain cleavage), which functions as the terminal oxidase in a mitochondrial electron-transfer chain where NADPH donated electrons to a flavoprotein (adrenodoxin reductase) which then transferred them to an iron-sulfur protein (adrenodoxin) which in turn donated them to P450scc (Kimura & Suzuki 1965, Omura et al 1966, Shikita & Hall 1973) (for review see Miller 1988). Thus Koizumi examined the total P450 in the affected adrenal mitochondria in the only fashion then available, by carbon monoxide-induced difference spectra, and concluded that affected mitochondria had roughly half of the normal amount of total cytochrome P450.…”

“…It was clear that adrenocorticotropin (ACTH) could induce adrenal steroidogenesis in a very rapid, cycloheximide-inhibitable fashion in all species studied: the 'acute response' (Stone & Hechter 1955, Ferguson 1963, Garren et al 1965, 1966. Work in the late 1980s showed that ACTH, working through cAMP as its second messenger, induced the transcription of the genes for P450scc and other steroidogenic enzymes (for review see Waterman & Simpson 1989, Moore & Miller 1991.…”

The Stoichiometry of the Conversion of Cholesterol and Hydroxycholesterols to Pregnenolone (3β-Hydroxypregn-5-en-20-one) Catalysed by Adrenal Cytochrome P -450

“…Acetone powder was prepared from adrenocortical mitochondria (4). A ratio of acetone to mitochondrial suspension of 5:1 was used.…”

Current status and future perspectives: TSPO in steroid neuroendocrinology

“…Enzymatic conversion of cholesterol by a mitochondrial cytochrome P450 side-chain cleavage (P450scc or CYP11A1) to generate PREG is the first and essential step for all steroid synthesis. The P450scc functions as the terminal oxidase in an electron-transfer chain where NADPH donated electrons to adrenodoxin reductase are transferred to adrenodoxin and then to P450scc (Kimura & Suzuki 1965, Omura et al 1966, Shikita & Hall 1973. Overall abundance of P450scc transcripts in the rat brain was estimated to be only ~0.01% of that measured in the adrenal gland (Mellon & Deschepper 1993), perhaps indicating that only a small subpopulation of cells are capable of de novo steroidogenesis.…”