Enzyme-bound sterols of bovine adrenocortical cytochrome P-450scc
- 17 February 1981
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 20 (4) , 925-929
- https://doi.org/10.1021/bi00507a043
Abstract
Bovine adrenocortical cytochrome P-450, capable of cleaving the side chain of cholesterol, was purified to homogeneity. The substrate-bound form of the enzyme preparation contained, 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/mol 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.Keywords
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