The Cholesterol Side-Chain Cleavage System of Bovine Adrenal Cortex

Abstract

1 The cholesterol side-chain cleavage system of bovine adrenal cortex has been studied using extracts of sonicated mitochondria as source of enzymic activity. 2 The system has been found to be inhibited by carbon monoxide, this inhibition being consistent with competition between carbon monoxide and oxygen for an enzymic site. 3 The inhibition by carbon monoxide is reversed by light, the most effective wavelength being 450 mμ. Thesé results suggest the involvement of a haem-containing protein, ‘P-450’ as the oxygen-binding site in the cholesterol side-chain cleavage system. 4 Attempts have been made to isolate intermediates between cholesterol and pregnenolone. Neither 20α-hydroxycholesterol nor 20α,22-dihydroxycholesterol have been found.