Involvement of cytochrome P450 3A4 in N-dealkylation of buprenorphine in human liver microsomes.
Buprenorphine is a long acting analgesic of the opiate family. Recently, it has been proposed for the opioid dependency treatment at a large scale. The drug is extensively metabolized by the hepatic cytochrome P450 in man, yielding a N-dealkylated metabolite, norbuprenorphine. The specific forms of P450 involved in this oxidative N-demethylation were examined in a panel of 18 human liver microsomal preparations previously characterized with respect to their P450 contents. Buprenorphine was N-dealkylated with an apparent Km of 89 +/- 45 microM (n = 3). The metabolic rates were 3.46 +/- 0.43 nmol/(min x mg of protein). This metabolic pathway was strongly correlated with 6 catalytic activities specific to P450 3A4 and with the immunodetectable P450 3A content of liver microsomal samples (r = 0.87). Buprenorphine metabolism was 62-71% inhibited by three mechanism-based inhibitors (TAO, erythralosamine, gestodene), by nifedipine as competitive inhibitor (Ki = 129 microM) and by ketoconazole 0.6 microM (25% residual activity), all these inhibitors specific to P450 3A. Among 10 heterologously expressed P450s tested, only P450 3A4 was able to dealkylate buprenorphine with a turnover number of 9.6 min(-1). Morever, this catalytic activity was inhibited up to 80% (vs control) by anti-rat P450 3A antibody. Taken together, all these data demonstrate that P450 3A4 is the major enzyme involved in hepatic buprenorphine N-dealkylation.
Iribarne
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Laboratoires de Biochimie-Nutrition - Equipe d'Accueil 948 - Faculté de Médecine, Brest, France.
Picart
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D
Dréano
Y
Y
Bail
J P
JP
Berthou
F
F
D000478:Alkylation; D002047:Buprenorphine / Q000037:antagonists & inhibitors / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006801:Humans; D008862:Microsomes, Liver / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009292:Narcotic Antagonists / Q000493:pharmacokinetics*; D013379:Substrate Specificity
D009292:Narcotic Antagonists; D002047:Buprenorphine; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A