title: Detergents as probes of reconstituted rat liver cytochrome P-450 function.
abstract: A series of 16 ionic, zwitterionic, and nonionic detergents have been used to perturb the catalytic activities of major cytochrome P-450 (P-450) forms from untreated (UT-A), phenobarbital-treated (PB-B) and beta-naphthoflavone-treated (BNF-B) rats in reconstituted systems with NADPH--P-450 reductase Detergent effects on R warfarin hydroxylase activities were correlated with detergent effects on the quaternary structures of P-450 and reductase, and on their 1:1 complexes as determined by gel exclusion chromatography using sodium cholate as a prototype detergent. The detergent concentrations used did not in most cases affect rates of NADPH-dependent reduction of cytochrome c by the reductase. With P-450 BNF-B, ionic and zwitterionic detergents enhanced warfarin hydroxylase activities at low concentrations and produced marked inhibition at higher concentrations, while nonionic detergents only inhibited. With P-450 UT-A, some nonionic and zwitterionic detergents increased rates at low concentrations and inhibited at higher concentrations. P-450 PB-B was inhibited by detergents of all three classes at low and high concentrations. The concentrations of a detergent required to affect 50% inhibition differed for the three P-450s, suggesting, together with the differential susceptibilities to detergent-mediated rate enhancing effects, that the reductase interacts functionally differently with the three P-450s. Chromatographic studies demonstrated that concentrations of sodium cholate which optimally enhanced metabolic rates with P-450 BNF-B facilitated the uptake of the P-450 into the functional reductase/P-450 complex, and higher concentrations of cholate, which completely inhibited activity, produced profound disruptions of the complex. The data have provided insight into the functional interactions required for monooxygenase activity.
mesh_terms: D000818:Animals; D001571:Benzoflavones / Q000494:pharmacology; D019826:Cholic Acid; D002793:Cholic Acids / Q000494:pharmacology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology*; D004790:Enzyme Induction; D006900:Hydroxylation; D007527:Isoenzymes / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D013501:Surface-Active Agents / Q000494:pharmacology*; D014859:Warfarin / Q000378:metabolism; D019324:beta-Naphthoflavone
chemical_list: D001571:Benzoflavones; D002793:Cholic Acids; D003574:Cytochrome c Group; D003902:Detergents; D007527:Isoenzymes; D013501:Surface-Active Agents; D014859:Warfarin; D019324:beta-Naphthoflavone; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase; D019826:Cholic Acid