Stereoselective inhibition of aromatase by enantiomers of aminoglutethimide.

The dextrorotatory enantiomer of aminoglutethimide is 38 times more potent than the levoenantiomer in inhibiting aromatization of testosterone by human placental microsomes. The spectral affinity constant for microsomal cytochrome P-450 is 36 times greater for the d-enantiomer. Enzymatic inhibition and affinity are highly correlated for each of the isomers as well as for the racemic mixture. Spectral analysis of the interactions of the inhibitors with the substrate supports the evidence for participation of cytochrome P-450 in aromatization.