MECHANISM OF OXIDATIVE AMINE DEALKYLATION OF SUBSTITUTED N,N-DIMETHYLANILINES BY CYTOCHROME-P-450 - APPLICATION OF ISOTOPE EFFECT PROFILES

Isotope effect profiles were determined for the deprotonation of a ser ies of para-substituted N-methyl-N(trideuteriomethyl)aniline cation ra dicals by pyridine and for hydrogen atom abstraction from the correspo nding neutral amines by the tert-butoxyl radical. The profiles model r eaction steps in two mechanisms commonly proposed for the oxidative de alkylation of amines by cytochrome P-450. Isotope effect profiles were also determined for the P-450 oxidation of the same set of N,N-bis(di deuteriomethyl)anilines by purified CYP2B1, expressed CYP2B1, phenobar bital-induced microsomal P-450, expressed CYP4B1, expressed CYP1A2, an d purified CYP102 (BM3). The profiles for all of the P-450 oxidations were found to be experimentally indistinguishable from the hydrogen at om abstraction profile, and distinctly different from the deprotonatio n profile. This agreement provides strong evidence that the P-450 oxid atively dealkylates the amines by a hydrogen atom abstraction mechanis m. Furthermore, the P-450 isotope effect profiles indicate that the re action mechanism is conserved in both mammalian and bacterial enzymes.