title: The effects of phosphatase on the components of the cytochrome P-450-dependent microsomal monooxygenase.
abstract: Incubation of rabbit liver microsomes with alkaline phosphatase resulted in a marked decrease of NADPH-dependent monooxygenase activities. This decrease was found to be correlated with the decrease of NADPH-cytochrome c reductase activity catalyzed by NADPH-cytochrome P-450 reductase. Neither the content of cytochrome P-450, as determined from its CO difference spectrum, nor the peroxide-supported demethylase activity catalyzed by cytochrome P-450 alone was affected by the phosphatase treatment. NADH-cytochrome b5 reductase and cytochrome b5 were not affected by the phosphatase either. NADPH-cytochrome P-450 reductase purified from rabbit liver microsomes lost its NADPH-dependent cytochrome c reductase activity upon incubation with phosphatase in a way similar to that of microsome-bound reductase. Flavin analysis showed that the phosphatase treatment caused a decrease of FMN with concomitant appearance of riboflavin. Alkaline phosphatase, therefore, inactivates the reductase by attacking its FMN, and the inactivation of the reductase, in turn, leads to a decrease of the microsomal monooxygenase activities.
mesh_terms: D015660:7-Alkoxycoumarin O-Dealkylase; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005486:Flavin Mononucleotide / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009249:NADP / Q000494:pharmacology; D009251:NADPH-Ferrihemoprotein Reductase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010710:Phosphates / Q000494:pharmacology; D011817:Rabbits; D012256:Riboflavin / Q000378:metabolism
chemical_list: D010710:Phosphates; D005182:Flavin-Adenine Dinucleotide; D009249:NADP; D005486:Flavin Mononucleotide; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010105:Oxygenases; D015660:7-Alkoxycoumarin O-Dealkylase; D009251:NADPH-Ferrihemoprotein Reductase; D000469:Alkaline Phosphatase; D012256:Riboflavin