Cytochrome P450 isozymes involved in propranolol metabolism in human liver microsomes

The role of CYP2D6 as ring-hydroxylase and CYP1A2 as N- desisopropylase

Y. Masubuchi, S. Hosokawa, T. Horie, T. Suzuki, S. Ohmori, M. Kitada, S. Narimatsu

Research output: Contribution to journalArticle

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Abstract

Oxidative metabolic pathways of propranolol consist of naphthalene ring- hydroxylations (at the 4-, 5-, and 7-positions) and side-chain N- desisopropylation in mammals. We characterized cytochrome P450 isozymes responsible for propranolol metabolism, especially N-desisopropylation and 5- hydroxylation, in human liver microsomes. 4-Hydroxy, 5-hydroxy-, and N- desisopropylpropranolol were detected as primary metabolites, whereas 7- hydroxypropranolol was in trace amounts. Good correlations were obtained for activities of propranolol 4- and 5-hydroxylases with immunochemically determined CYP2D6 content, whereas correlations of these activities with CYP1A2, CYP2C, or CYP3A4 content were relatively low. The activities also correlated highly with debrisoquine 4-hydroxylase, compared with other metabolic activities such as phenacetin O-deethylase, hexobarbital 3'- hydroxylase, and testosterone 6β-hydroxylase, which are typical reactions for CYP1A2, CYP2C, and CYP3A4, respectively. Propranolol N-desisopropylase activity in the samples highly correlated with CYP1A2 content and phenacetin O-deethylase activity, but not with the other P450 isozyme contents or metabolic activities. Quinidine, a specific inhibitor of CYP2D6, inhibited propranolol 4- and 5-hydroxylase activities selectively and in a concentration-dependent manner. α-Naphthoflavone, a potent inhibitor of CYP1A2, inhibited all of the propranolol oxidation activities, and the IC50 value for N-desisopropylase activity was much smaller than the values for ring-hydroxylase activities. Antibody directed to CYP2D inhibited propranolol 4- and 5-hydroxylase activities by 70% at an antibody/microsomal protein ratio of 1.0. Anti-CYP2C9 antibody did not inhibit any activity determined. These results indicate that propranolol 5-hydroxylation, as well as 4- hydroxylation, is mainly catalyzed by CYP2D6 in human liver microsomes. Furthermore, CYP1A2, rather than S-mephenytoin 4-hydroxylase, seems to be responsible for propranolol N-desisopropylation.

Original languageEnglish
Pages (from-to)909-915
Number of pages7
JournalDrug Metabolism and Disposition
Volume22
Issue number6
Publication statusPublished - 1994
Externally publishedYes

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Cytochrome P-450 CYP1A2
Cytochrome P-450 CYP2D6
Liver Microsomes
Mixed Function Oxygenases
Metabolism
Propranolol
Liver
Cytochrome P-450 Enzyme System
Isoenzymes
Hydroxylation
Phenacetin
Cytochrome P-450 CYP3A
Antibodies
Hexobarbital
Quinidine
Mammals
Metabolites
Metabolic Networks and Pathways
Inhibitory Concentration 50
Testosterone

ASJC Scopus subject areas

  • Pharmacology
  • Toxicology

Cite this

Cytochrome P450 isozymes involved in propranolol metabolism in human liver microsomes : The role of CYP2D6 as ring-hydroxylase and CYP1A2 as N- desisopropylase. / Masubuchi, Y.; Hosokawa, S.; Horie, T.; Suzuki, T.; Ohmori, S.; Kitada, M.; Narimatsu, S.

In: Drug Metabolism and Disposition, Vol. 22, No. 6, 1994, p. 909-915.

Research output: Contribution to journalArticle

Masubuchi, Y. ; Hosokawa, S. ; Horie, T. ; Suzuki, T. ; Ohmori, S. ; Kitada, M. ; Narimatsu, S. / Cytochrome P450 isozymes involved in propranolol metabolism in human liver microsomes : The role of CYP2D6 as ring-hydroxylase and CYP1A2 as N- desisopropylase. In: Drug Metabolism and Disposition. 1994 ; Vol. 22, No. 6. pp. 909-915.
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abstract = "Oxidative metabolic pathways of propranolol consist of naphthalene ring- hydroxylations (at the 4-, 5-, and 7-positions) and side-chain N- desisopropylation in mammals. We characterized cytochrome P450 isozymes responsible for propranolol metabolism, especially N-desisopropylation and 5- hydroxylation, in human liver microsomes. 4-Hydroxy, 5-hydroxy-, and N- desisopropylpropranolol were detected as primary metabolites, whereas 7- hydroxypropranolol was in trace amounts. Good correlations were obtained for activities of propranolol 4- and 5-hydroxylases with immunochemically determined CYP2D6 content, whereas correlations of these activities with CYP1A2, CYP2C, or CYP3A4 content were relatively low. The activities also correlated highly with debrisoquine 4-hydroxylase, compared with other metabolic activities such as phenacetin O-deethylase, hexobarbital 3'- hydroxylase, and testosterone 6β-hydroxylase, which are typical reactions for CYP1A2, CYP2C, and CYP3A4, respectively. Propranolol N-desisopropylase activity in the samples highly correlated with CYP1A2 content and phenacetin O-deethylase activity, but not with the other P450 isozyme contents or metabolic activities. Quinidine, a specific inhibitor of CYP2D6, inhibited propranolol 4- and 5-hydroxylase activities selectively and in a concentration-dependent manner. α-Naphthoflavone, a potent inhibitor of CYP1A2, inhibited all of the propranolol oxidation activities, and the IC50 value for N-desisopropylase activity was much smaller than the values for ring-hydroxylase activities. Antibody directed to CYP2D inhibited propranolol 4- and 5-hydroxylase activities by 70{\%} at an antibody/microsomal protein ratio of 1.0. Anti-CYP2C9 antibody did not inhibit any activity determined. These results indicate that propranolol 5-hydroxylation, as well as 4- hydroxylation, is mainly catalyzed by CYP2D6 in human liver microsomes. Furthermore, CYP1A2, rather than S-mephenytoin 4-hydroxylase, seems to be responsible for propranolol N-desisopropylation.",
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T2 - The role of CYP2D6 as ring-hydroxylase and CYP1A2 as N- desisopropylase

AU - Masubuchi, Y.

AU - Hosokawa, S.

AU - Horie, T.

AU - Suzuki, T.

AU - Ohmori, S.

AU - Kitada, M.

AU - Narimatsu, S.

PY - 1994

Y1 - 1994

N2 - Oxidative metabolic pathways of propranolol consist of naphthalene ring- hydroxylations (at the 4-, 5-, and 7-positions) and side-chain N- desisopropylation in mammals. We characterized cytochrome P450 isozymes responsible for propranolol metabolism, especially N-desisopropylation and 5- hydroxylation, in human liver microsomes. 4-Hydroxy, 5-hydroxy-, and N- desisopropylpropranolol were detected as primary metabolites, whereas 7- hydroxypropranolol was in trace amounts. Good correlations were obtained for activities of propranolol 4- and 5-hydroxylases with immunochemically determined CYP2D6 content, whereas correlations of these activities with CYP1A2, CYP2C, or CYP3A4 content were relatively low. The activities also correlated highly with debrisoquine 4-hydroxylase, compared with other metabolic activities such as phenacetin O-deethylase, hexobarbital 3'- hydroxylase, and testosterone 6β-hydroxylase, which are typical reactions for CYP1A2, CYP2C, and CYP3A4, respectively. Propranolol N-desisopropylase activity in the samples highly correlated with CYP1A2 content and phenacetin O-deethylase activity, but not with the other P450 isozyme contents or metabolic activities. Quinidine, a specific inhibitor of CYP2D6, inhibited propranolol 4- and 5-hydroxylase activities selectively and in a concentration-dependent manner. α-Naphthoflavone, a potent inhibitor of CYP1A2, inhibited all of the propranolol oxidation activities, and the IC50 value for N-desisopropylase activity was much smaller than the values for ring-hydroxylase activities. Antibody directed to CYP2D inhibited propranolol 4- and 5-hydroxylase activities by 70% at an antibody/microsomal protein ratio of 1.0. Anti-CYP2C9 antibody did not inhibit any activity determined. These results indicate that propranolol 5-hydroxylation, as well as 4- hydroxylation, is mainly catalyzed by CYP2D6 in human liver microsomes. Furthermore, CYP1A2, rather than S-mephenytoin 4-hydroxylase, seems to be responsible for propranolol N-desisopropylation.

AB - Oxidative metabolic pathways of propranolol consist of naphthalene ring- hydroxylations (at the 4-, 5-, and 7-positions) and side-chain N- desisopropylation in mammals. We characterized cytochrome P450 isozymes responsible for propranolol metabolism, especially N-desisopropylation and 5- hydroxylation, in human liver microsomes. 4-Hydroxy, 5-hydroxy-, and N- desisopropylpropranolol were detected as primary metabolites, whereas 7- hydroxypropranolol was in trace amounts. Good correlations were obtained for activities of propranolol 4- and 5-hydroxylases with immunochemically determined CYP2D6 content, whereas correlations of these activities with CYP1A2, CYP2C, or CYP3A4 content were relatively low. The activities also correlated highly with debrisoquine 4-hydroxylase, compared with other metabolic activities such as phenacetin O-deethylase, hexobarbital 3'- hydroxylase, and testosterone 6β-hydroxylase, which are typical reactions for CYP1A2, CYP2C, and CYP3A4, respectively. Propranolol N-desisopropylase activity in the samples highly correlated with CYP1A2 content and phenacetin O-deethylase activity, but not with the other P450 isozyme contents or metabolic activities. Quinidine, a specific inhibitor of CYP2D6, inhibited propranolol 4- and 5-hydroxylase activities selectively and in a concentration-dependent manner. α-Naphthoflavone, a potent inhibitor of CYP1A2, inhibited all of the propranolol oxidation activities, and the IC50 value for N-desisopropylase activity was much smaller than the values for ring-hydroxylase activities. Antibody directed to CYP2D inhibited propranolol 4- and 5-hydroxylase activities by 70% at an antibody/microsomal protein ratio of 1.0. Anti-CYP2C9 antibody did not inhibit any activity determined. These results indicate that propranolol 5-hydroxylation, as well as 4- hydroxylation, is mainly catalyzed by CYP2D6 in human liver microsomes. Furthermore, CYP1A2, rather than S-mephenytoin 4-hydroxylase, seems to be responsible for propranolol N-desisopropylation.

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