title: Posttranslational modifications of the cytochrome P-450 monooxygenase system.
abstract: Two forms of enzymatic posttranslational modifications of the monooxygenase system are described: modification by phosphatase and modification by protein kinase. Phosphatase treatment of microsomes isolated from phenobarbital-pretreated rabbits and rats caused a marked decrease of monooxygenase activity which was paralleled by a comparable decrease of NADPH-cytochrome P-450 reductase activity while the second essential component of the system, cytochrome P-450, remained unaltered. Thus phosphatase attacks monooxygenase via reductase. Protein kinases showed the opposite preference; while cytochrome P-450 was phosphorylated, NADPH-cytochrome P-450 reductase was not. Thus the kinase affects monooxygenase via cytochrome P-450. The phosphorylation of cytochrome P-450 turned out to be a specific reaction observed only with certain cytochrome P-450 isoenzymes and certain protein kinases.
mesh_terms: D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003580:Cytochromes / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D051381:Rats
chemical_list: D003580:Cytochromes; C013464:cytochrome P420; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases