Stereoselective inhibition of cholesterol side chain cleavage by enantiomers of aminoglutethimide.

Because aminoglutethimide is a potentially important drug in the treatment of certain maligancies as well as fertility control, its stereoisomers were studied for binding to corpus luteum mitochondrial cytochrome P-450 and inhibition of cholesterol side chain cleavage. The binding affinity, determined from induced spectral changes, is 2.6 times greater for the d- than for the l-isomer. In the enzyme assay, the d-isomer is 2.5 times more potent as an inhibitor of cholesterol side chain cleavage than is the l-isomer. The extent of inhibition and the change in the absorptivity of the P-450-inhibitor complex are linearly related for both chiral and racemic forms. Thus, the active center of the enzyme is stereoselective for the enantiomers of aminoglutethimide.