Differential N-Demethylation of l-α-Acetylmethadol (LAAM) and norLAAM by Cytochrome P450s 2B6, 2C18, and 3A4
| Autor: | Jennifer Neff, David E. Moody |
|---|---|
| Rok vydání: | 2001 |
| Předmět: |
Cytochrome
Methadyl Acetate Biophysics Spodoptera Transfection Methylation Biochemistry Isozyme Mixed Function Oxygenases Acetylmethadol chemistry.chemical_compound Cytochrome P-450 Enzyme System Microsomes Cytochrome b5 Animals Cytochrome P-450 CYP3A Humans Molecular Biology Incubation Demethylation biology Chemistry Oxidoreductases N-Demethylating Cell Biology Metabolism Cytochrome P-450 CYP2B6 Liver Microsome biology.protein Aryl Hydrocarbon Hydroxylases |
| Zdroj: | Biochemical and Biophysical Research Communications. 284:751-756 |
| ISSN: | 0006-291X |
| DOI: | 10.1006/bbrc.2001.5054 |
| Popis: | Incubation of l-α-acetylmethadol (LAAM) or norLAAM with cDNA-expressed P450s 3A4, 2B6, and 2C18 produced significant N-demethylation products. P450s 2C19, 2C8, 3A5, 2C9, 3A7, 1A1, and 2D6 (norLAAM only), also produced detectable product. Coexpression of cytochrome b5 enhanced LAAM N-demethylation, most dramatically for 3A4, but had marginal effects on norLAAM N-demethylation. Modeling total liver metabolism using immunoquantification and relative activity factors of P450s suggests contributions of P450 3A4 > 2B6 > 2C18, with the importance of 2B6 to 2C isozymes enhanced by relative activity factors. The ratio of dinorLAAM to norLAAM plus dinorLAAM formed from LAAM did not exceed 20%, and was isozyme and cytochrome b5 coexpression dependent. This ratio decreased with concentration with 3A4, but was relatively constant for 2B6 and 2C18. The human liver microsomes substrate-concentration response was similar to cDNA-expressed 3A4, but the ratio was higher. Changes in the environment of cDNA-expressed 3A4 also effected the magnitude of the ratio, but not the concentration-dependent decrease. These studies show that the N-demethylation of LAAM and norLAAM is not restricted to P450 3A4, particularly P450s 2B6 and 2C18, and suggest that the mechanism of sequential metabolism for 3A4 differs from that of 2B6 and 2C18. |
| Databáze: | OpenAIRE |
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