Allosteric activation of cytochrome P450 3A4 by α-naphthoflavone: branch point regulation revealed by isotope dilution analysis.

ABSTRACT: Cytochrome P450 3A4 (CYP3A4) is the dominant xenobiotic metabolizing CYP. Despite great interest in CYP enzymology, two in vitro aspects of CYP3A4 catalysis are still not well understood, namely, sequential metabolism and allosteric activation. We have therefore investigated such a system in which both phenomena are present. Here we report that the sequential metabolism of Nile Red (NR) is accelerated by the heterotropic allosteric effector α-naphthoflavone (ANF). ANF increases the rates of formation for NR metabolites M1 and M2 and also perturbs the metabolite ratio in favor of M2. Thus, ANF has as an allosteric effect on a kinetic branch point. Co-incubating deuterium-labeled NR and unlabeled M1, we show that ANF increases k(cat)/k(off) ~1.8-fold in favor of the k(cat) of M2 production.

SUBMITTER: Woods CM 

PROVIDER: S-EPMC3226823 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature