Enzyme-bound sterols of bovine adrenocortical cytochrome P-450scc.
Bovine adrenocortical cytochrome P-450 capable of cleaving the side chain of cholesterol was purified to homogeneity by the method of Suhara et al. [Suhara, K., Gomi, T., Sato, H., Itagaki, E., Takemori, S., & Katagiri, M. (1978) Arch. Biochem Biophys. 190, 290]. The substrate-bound form of the enzyme preparation was shown to contain in addition to cholesterol (1.2-3.0 mol/mol of P-450) 0.4 mol of (22R)-22-hydroxycholesterol, 0.1 mol of (20R,22R)-20,22-dihydroxycholesterol, and a trace amount (0.005 mol) of (20S)-20-hydroxycholesterol per mol of P-450scc. This relatively large concentration of (22R)-22-hydroxycholesterol is in accord with the hypothesis that the major pathway leading to side-chain cleavage proceeds through initial hydroxylation at the 22 position. The presence of these sterols as native constituents of cytochrome P-450scc supports their role as enzyme-bound intermediates in the biosynthesis of pregnenolone from cholesterol.
D000302:Adrenal Cortex / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002784:Cholesterol / Q000378:metabolism*; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006888:Hydroxycholesterols / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism*; D013053:Spectrophotometry
D006888:Hydroxycholesterols; D003577:Cytochrome P-450 Enzyme System; D002784:Cholesterol