CAFFEINE AS A PROBE FOR HUMAN CYTOCHROMES-P450 - VALIDATION USING CDNA-EXPRESSION, IMMUNOINHIBITION AND MICROSOMAL KINETIC AND INHIBITOR TECHNIQUES

被引：109

作者：

TASSANEEYAKUL, W ^{[1
]}

MOHAMED, Z ^{[1
]}

BIRKETT, DJ ^{[1
]}

MCMANUS, ME ^{[1
]}

VERONESE, ME ^{[1
]}

TUKEY, RH ^{[1
]}

QUATTROCHI, LC ^{[1
]}

GONZALEZ, FJ ^{[1
]}

MINERS, JO ^{[1
]}

机构：

[1] FLINDERS UNIV S AUSTRALIA,MED CTR,DEPT CLIN PHARMACOL,BEDFORD PK,SA 5042,AUSTRALIA

来源：

PHARMACOGENETICS | 1992年 / 2卷 / 04期

关键词：

D O I：

10.1097/00008571-199208000-00004

中图分类号：

Q81 [生物工程学（生物技术）]; Q93 [微生物学];

学科分类号：

071005 ; 0836 ; 090102 ; 100705 ;

摘要：

The molecular basis for the use of caffeine (CA; 1,3,7-trimethylxanthine) as a probe for specific human cytochromes P450 has been investigated. The CA 1-, 3- and 7-demethylations (to form theobromine, paraxanthine and theophylline, respectively) all followed biphasic kinetics in human liver microsomes. Mean apparent K(m) values for the high- and low-affinity components of the demethylations ranged from 0.13-0.31 mM and 19.2-30.0 mM, respectively. cDNA-expressed CYP1A2 catalysed all three CA demethylations, and the apparent K(m) for CA 3-demethylation (the major metabolic pathway in humans) by the expressed enzyme was similar to the K(m) for the high-affinity liver microsomal CA 3-demethylase. IC50 values for inhibition of the CA demethylations by alpha-naphthoflavone were similar for both expressed CYP1A2 and the high-affinity microsomal demethylases. Moreover, CA was a competitive inhibitor of expressed CYP1A2 catalysed phenacetin 0-deethylation, with the apparent K(i) (0.080 mM) closely matching the apparent K(m) (0.082 mM) for CA 3-demethylation by the expressed enzyme. Expressed CYP1A1 was additionally shown to catalyse the 3-demethylation of CA, although activity was lower than that observed for CYP1A2. While these data indicate that CYP1A2 is responsible for the high-affinity component of human liver CA 3-demethylation, two limitations associated with the use of CA as an in vitro probe for CYP1A2 activity have been identified: (i) CA 3-demethylation reflects hepatic CYP1A2 activity only at appropriately low substrate concentrations; and (ii) CA is a non-specific CYP1A substrate and CYP1A1 may therefore contribute to CA 3-demethylase activity in tissues in which it is expressed. An anti-CYP3A antibody essentially abolished the 8-hydroxylation of CA to form trimethyluric acid, suggesting formation of this metabolite may potentially serve as a marker of CYP3A isozyme(s) activity.

引用

页码：173 / 183

页数：11

共 48 条

[1] Aldridge A., Parsons W.D., Neims A.H., Stimulation of caffeine metabolism in the rat by 3-methylcholanthrene, Life Sci, 21, pp. 967-974, (1977)
[2] Aoyama T., Yamano S., Waxman D.J., Lapenson D.P., Meyer U.A., Fisher V., Tyndale R., Inaba T., Kalow W., Gelboin H.V., Gonzalez F.J., Cytochrome P450 hPCN3, a novel P450IIIA gene product that is differentially expressed in adult human liver: CDNA and deduced amino acid sequence and distinct specificities of cDNA expressed hPCNl and hPCN3 for the metabolism of steroid hormones and cyclosporine, J Biol Chem, 264, pp. 10388-10393, (1989)
[3] Aoyama T., Korzekwa K., Nagata K., Gillette J., Gelboin H.V., Gonzalez F.J., Estradiol metabolism by complementary deoxyribonucleic acid-expressed human cytochrome P450s, Endocrinology, 126, pp. 3101-3106, (1990)
[4] Apseloff G., Shepard D.R., Chambers M.A., Nawoot S., Mays D.C., Gerber N., Inhibition and induction of theophylline metabolism by 8-methoxypsoralen, Drug Metab Disp, 18, pp. 293-303, (1990)
[5] Berthou F., Ratanasavanh D., Riche C., Picart D., Voirin T., Guillouzo A., Comparison of caffeine metabolism by slices, microsomes and hepatocyte cultures from adult human liver, Xenobiotica, 19, pp. 401-417, (1989)
[6] Berthou F., Flinois J.P., Ratanasavanh D., Beaune P., Riche C., Guillouzo A., Evidence for the involvement of several cytochromes P450 in the first steps of caffeine metabolism by human liver microsomes, Drug Metab Disp, 19, pp. 561-567, (1991)
[7] Birkett D.J., Miners J.O., Attwood J., Secondary metabolism of theophylline biotransformation products in man-Route of formation of 1-methyluracil, Br J Clin Pharmacol, 15, pp. 117-119, (1983)
[8] Butler M.A., Iwasaki M., Guengerich F.P., Kadlubar F.F., Human cytochrome P450pa (P450IA2), the phenacetin O-deethylase, is primarily responsible for the hepatic 3-demethylation of caffeine and N-oxidation of carcinogenic arylamines, Proc Natl Acad Sci USA, 86, pp. 7696-7700, (1989)
[9] Callahan M.M., Robertson R.S., Branfman A.R., Mc Comish M.F., Yesair D.W., Human metabolism of [l-methyl-14C]- and [2-14C]- caffeine after oral administration, Drug Metab Disp, 10, pp. 417-423, (1982)
[10] Campbell M.E., Grant D.M., Inaba T., Kalow W., Biotransformation of caffeine, paraxanthine, theophylline and theobromine by polycyclic aromatic hydrocarbon-inducible cytochromes P450 in human liver microsomes, Drug Metab Disp, 15, pp. 237-249, (1987)

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