title: Monkey liver cytochrome P450 2C9 is involved in caffeine 7-N-demethylation to form theophylline.
abstract: Caffeine (1,3,7-trimethylxanthine) is a phenotyping substrate for human cytochrome P450 1A2. 3-N-Demethylation of caffeine is the main human metabolic pathway, whereas monkeys extensively mediate the 7-N-demethylation of caffeine to form pharmacological active theophylline. Roles of monkey P450 enzymes in theophylline formation from caffeine were investigated using individual monkey liver microsomes and 14 recombinantly expressed monkey P450 enzymes, and the results were compared with those for human P450 enzymes. Caffeine 7-N-demethylation activity in microsomes from 20 monkey livers was not strongly inhibited by α-naphthoflavone, quinidine or ketoconazole, and was roughly correlated with diclofenac 4'-hydroxylation activities. Monkey P450 2C9 had the highest activity for caffeine 7-N-demethylation. Kinetic analysis revealed that monkey P450 2C9 had a high Vmax/Km value for caffeine 7-N-demethylation, comparable to low Km value for monkey liver microsomes. Caffeine could dock favorably with monkey P450 2C9 modeled for 7-N-demethylation and with human P450 1A2 for 3-N-demethylation. The primary metabolite theophylline was oxidized to 8-hydroxytheophylline in similar ways by liver microsomes and by recombinant P450s in both humans and monkeys. These results collectively suggest a high activity for monkey liver P450 2C9 toward caffeine 7-N-demethylation, whereas, in humans, P450 1A2-mediated caffeine 3-N-demethylation is dominant.
authors.affiliation: Shin Nippon Biomedical Laboratories, Ltd., Pharmacokinetics and Bioanalysis Center , Kainan , Japan .
authors.forename: Masahiro
authors.initials: M
authors.lastname: Utoh
authors.forename: Norie
authors.initials: N
authors.lastname: Murayama
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Uno
authors.forename: Yui
authors.initials: Y
authors.lastname: Onose
authors.forename: Shinya
authors.initials: S
authors.lastname: Hosaka
authors.forename: Hideki
authors.initials: H
authors.lastname: Fujino
authors.forename: Makiko
authors.initials: M
authors.lastname: Shimizu
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Iwasaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamazaki
mesh_terms: D000818:Animals; D002110:Caffeine / Q000737:chemistry / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000882:Haplorhini / Q000378:metabolism*; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D008745:Methylation / Q000187:drug effects; D008862:Microsomes, Liver / Q000201:enzymology; D062105:Molecular Docking Simulation; D010084:Oxidation-Reduction / Q000187:drug effects; D011994:Recombinant Proteins / Q000378:metabolism; D013806:Theophylline / Q000737:chemistry / Q000378:metabolism*
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D002110:Caffeine; D003577:Cytochrome P-450 Enzyme System; D013806:Theophylline