The non-linear dependence of cytochrome P450 activity at low microsome concentration.
A non-linear decrease in the activity of cytochrome P450-dependent (P450) ethoxyphenoxazone deethylase was observed with intact rat liver and lung microsomal fractions, although all components of the P450 complex were present. Activity was restored by adding pre-heated microsomal membranes or synthetic phospholipid, or by concentrating the diluted preparation. Aqueous dilution of the microsomal fraction resulted in altered Vmax values, whereas Km(app) values (0.2 microM) were only slightly changed. The results are discussed in terms of the relationship between cytochrome P450 action in model systems and in native microsomal membranes.
National Institute for Occupational Safety and Health, Division of Respiratory Disease Studies, Morgantown, WV 26505.
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Rabovsky
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D000818:Animals; D019363:Cytochrome P-450 CYP1A1; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004134:Dimyristoylphosphatidylcholine / Q000494:pharmacology; D007700:Kinetics; D008168:Lung / Q000201:enzymology / Q000648:ultrastructure; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D010088:Oxidoreductases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013050:Spectrometry, Fluorescence
D003577:Cytochrome P-450 Enzyme System; D010088:Oxidoreductases; D019363:Cytochrome P-450 CYP1A1; D004134:Dimyristoylphosphatidylcholine