title: Factors involved in the regulation of the levels and activities of rat liver cytochromes P-450.
abstract: Methods have been developed for the purification of eight rat liver microsomal cytochrome P-450 (P-450) isoenzymes. Another rat P-450, responsible for the metabolism of the genetic polymorphism prototype debrisoquine, has also been partially purified from rat liver. Six P-450s have been purified to electrophoretic homogeneity from human liver preparations. The rat and human P-450s can be quantified in crude samples using 'immunoblotting' methods coupled with peroxidase visualization. A study on the effects of a family of polybrominated biphenyl congeners led to the conclusion that the levels of all of the rat P-450s considered above are under some degree of independent regulation. In monolayer culture, different P-450s show different stabilities and levels of several are selectively regulated by various media components. Studies with the eight isolated rat P-450s indicate that the iron spin state, oxidation-reduction potential (Fe3+/Fe2+ couple), and catalytic activity towards substrates are not related to each other. The major function of phospholipid in reconstituted P-450/NADPH-P-450 reductase systems is the facilitation of formation of a complex of the two proteins. Studies on the regioselective hydroxylation of warfarin have been used to develop an order of binding affinity of the different P-450s for NADPH-P-450 reductase.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System; D009251:NADPH-Ferrihemoprotein Reductase