Substrate probes for the mechanism of aromatic hydroxylation catalyzed by cytochrome P-450: selectively deuterated analogues of warfarin.
Optically pure analogues of (R)- and (S)-warfarin selectively deuterated in either the 6-, 7-, or 8-position were prepared and incubated with microsomal preparations from either nontreated, phenobarbital-pretreated, or beta-naphthoflavone-pretreated male Sprague-Dawley rats. The amount of deuterium retained and the relative amount of hydroxylated product formed (6-, 7-, 8-, or 4'-hydroxywarfarin) from each of the six substrates for each of the treatments were determined by capillary gas chromatography-mass spectrometry. The degree of deuterium retention in all products from all substrates was largely independent of both absolute configuration and induction state. Conversely, the relative amounts of product formed were highly dependent upon both absolute configuration and induction state. These results suggest that all the hydroxylation reactions proceed through an addition rearrangement step prior to or in the absence of epoxide formation, which appears to be dictated by the nature of the heme-Fe3+-oxene complex. In contrast, the position of hydroxylation or regioselectivity appears to be primarily dependent upon the nature of the apoprotein.
D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003903:Deuterium; D006900:Hydroxylation; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism; D013379:Substrate Specificity; D014859:Warfarin / Q000031:analogs & derivatives* / Q000378:metabolism
D014859:Warfarin; D003577:Cytochrome P-450 Enzyme System; D003903:Deuterium