The multi-step oxidation of cholesterol to pregnenolone by human cytochrome P450 11A1 is highly processive.

ABSTRACT: Cytochrome P450 (P450, CYP) 11A1 is the classical cholesterol side chain cleavage enzyme (P450_scc) that removes six carbons of the side chain, the first and rate-limiting step in the synthesis of all mammalian steroids. The reaction is a 3-step, 6-electron oxidation that proceeds via formation of 22R-hydroxy (OH) and 20R,22R-(OH)₂ cholesterol, yielding pregnenolone. We expressed human P450 11A1 in bacteria, purified the enzyme in the absence of non-ionic detergents, and assayed pregnenolone formation by HPLC-mass spectrometry of the dansyl hydrazone. The reaction was inhibited by the nonionic detergent Tween 20, and several lipids did not enhance enzymatic activity. The 22R-OH and 20R,22R-(OH)₂ cholesterol intermediates were bound to P450 11A1 relatively ti

SUBMITTER: McCarty KD 

PROVIDER: S-EPMC10716780 | biostudies-literature | 2023 Nov

REPOSITORIES: biostudies-literature