A fluorescence study of the interactions of benzo[a]pyrene, cytochrome P450c and NADPH-cytochrome P450 reductase.
Fluorescence quenching of benzo[a]pyrene (BP) by cytochrome P450c was used to probe this substrate-enzyme binding interaction. Addition of NADPH-cytochrome P450 reductase, an essential electron carrier during P450 catalysis, resulted in increased quenching and thus strengthened binding of BP to P450c. This shows that the role of reductase extends beyond that of an electron transfer agent to influence substrate binding. Fluorescence titration measurements revealed that reductase and P450c formed a complex with an apparent KD of 13.7 +/- 0.9 nM. Reductase had no effect in the presence of an anti-P450c monoclonal antibody which inhibits BP hydroxylation, which suggests that this monoclonal antibody binds P450c near its reductase binding region.
Omata
Y
Y
Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Friedman
F K
FK
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001564:Benzo(a)pyrene / Q000378:metabolism*; D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000276:immunology / Q000378:metabolism*; D004347:Drug Interactions; D008297:Male; D008930:Mitochondria, Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D013050:Spectrometry, Fluorescence
D000911:Antibodies, Monoclonal; D001564:Benzo(a)pyrene; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase