title: Investigations on the role of cytochrome b5 and divalent cations in the maximal nifedipine oxidase activity of human liver.
abstract: Native human cytochrome P4503A4 was most active in nifedipine oxidation when incorporated into a binary phospholipid vesicular system with human NADPH-cytochrome P450 reductase. The turnover numbers were estimated to be 17.6 and 19.6 min-1 in the presence of Mg2+ or Ca2+ ions (5 mmol/l) in the test system, respectively. Inclusion of b5 in the vesicular CYP3A4: reductase system results in a slightly lower nifedipine oxidase activity of 16.9 min-1 in the presence of Mg2+ ions. These results demonstrate that b5 is not an essential component in CYP3A4 catalyzed nifedipine oxidation in human liver.
authors.affiliation: Department of Physiological Chemistry, Universität of Ulm, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Müller-Enoch
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D020355:Cholates / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D015786:Cytochromes b5 / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D011817:Rabbits; D051381:Rats
chemical_list: D002413:Cations, Divalent; D020355:Cholates; D010743:Phospholipids; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D009251:NADPH-Ferrihemoprotein Reductase; D005978:Glutathione; D008274:Magnesium; D002118:Calcium