title: Cytochrome P450 isoenzymes involved in rat liver microsomal metabolism of californine and protopine.
abstract: Studies are described on the cytochrome P450 (CYP) isoenzyme dependence of the main metabolic steps of the Eschscholtzia californica alkaloids californine and protopine using rat liver microsomes. Preparations of E. californica are in use as phytopharmaceuticals and as herbal drugs of abuse. CYP isoenzyme dependences were studied using specific chemical inhibitors for CYP1A2, CYP2D1, and CYP3A2 (alpha-naphthoflavone, quinine, and ketoconazole, respectively). CYP2C11 was inhibited by specific antibodies for lack of specific chemical inhibitors. Californine N-demethylation was mainly catalyzed by CYP3A2 and to a minor extent by CYP1A2 and CYP2D1, but not by CYP2C11. CYP2D1 and CYP2C11 were shown to be mainly involved in demethylenation of both, californine and protopine, while CYP1A2 and CYP3A2 showed only minor contribution. Kinetic parameters of the reactions were established. K(m) and V(max) values for the californine N-demethylation were 4.5+/-4.7 microM and 22.9+/-13.7 min/mg protein (high affinity) and 161.3+/-16.7 microM and 311.8+/-39.4 min/mg protein (low affinity), respectively. Californine demethylenation and protopine demethylenation showed substrate inhibition and K(m) and V(max) values were 5.0+/-0.5 and 7.1+/-0.6 microM and 83.3+/-2.6 and 160.7+/-4.0 min/mg protein, respectively.
authors.affiliation: Department of Experimental and Clinical Toxicology, Institute of Experimental and Clinical Pharmacology and Toxicology, University of Saarland, D-66421 Homburg (Saar), Germany.
authors.forename: Liane D
authors.initials: LD
authors.lastname: Paul
authors.forename: Dietmar
authors.initials: D
authors.lastname: Springer
authors.forename: Roland F
authors.initials: RF
authors.lastname: Staack
authors.forename: Thomas
authors.initials: T
authors.lastname: Kraemer
authors.forename: Hans H
authors.initials: HH
authors.lastname: Maurer
mesh_terms: D000429:Alcohol Oxidoreductases; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors; D053119:Benzophenanthridines; D001600:Berberine Alkaloids / Q000737:chemistry / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000502:physiology*; D000072467:Cytochrome P450 Family 2; D004305:Dose-Response Relationship, Drug; D007527:Isoenzymes / Q000502:physiology; D007546:Isoquinolines / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000037:antagonists & inhibitors; D008745:Methylation; D008862:Microsomes, Liver / Q000201:enzymology* / Q000378:metabolism; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D039181:Steroid 16-alpha-Hydroxylase / Q000037:antagonists & inhibitors
chemical_list: D053119:Benzophenanthridines; D001600:Berberine Alkaloids; D007527:Isoenzymes; D007546:Isoquinolines; D008565:Membrane Proteins; C481249:californine; D003577:Cytochrome P-450 Enzyme System; D011803:Quinine; D000429:Alcohol Oxidoreductases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; C504568:Cyp2d1 protein, rat; C465260:Cyp3a2 protein, rat; D051544:Cytochrome P-450 CYP3A; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; C009093:protopine