Abstract
The O-demethylation of dextromethorphan to dextrorphan in humans is catalyzed primarily by cytochrome P450 2D6 (CYP2D6). However, contrary to conventional wisdom, preparations of recombinant cytochrome P450 (P450) expressed from CYP2D6*1 cDNA also appear to produce significant amounts of 3-methoxymorphinan, the N-demethylated metabolite of dextromethorphan, when assayed in vitro, We hypothesized that both pathways were intrinsic to 2D6 and here further examine the kinetics of formation using a highly purified preparation of CYP2D6 in a reconstituted lipid system. Purified CYP2D6 protein with a measured molecular weight of 55772.0 (55769.6 Da predicted) was reconstituted into an active, lipid-vesicle environment with purified rat cytochrome P450 reductase before the addition of substrate and NADPH. Reaction kinetics were followed, and apparent Michaelis-Menten constants were determined for the appearance of each metabolite by high-pressure liquid chromatography, using both UV and fluorescence detection. In a 2-min assay, purified 2D6 catalyzed the formation of dextrorphan with an apparent Km value of 1.9 ± 0.2 μM and a Vmax value of 8.5 ± 0.2 nmol/nmol of P450/min and measured simultaneously the formation of 3-methoxymorphinan with an apparent Km value of 5000 ± 700 μM and Vmax value of 176 ± 12 nmol (nmol of P450)-1 min-1. These results indicate that at least two distinct binding orientations exist for dextromethorphan within the active site of CYP2D6.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 1362-1365 |
| Number of pages | 4 |
| Journal | Drug Metabolism and Disposition |
| Volume | 29 |
| Issue number | 11 |
| State | Published - 2001 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Pharmacology
- Toxicology
Cite this
Characterization of dextromethorphan O- and N-demethylation catalyzed by highly purified recombinant human CYP2D6. / Yu, Aiming; Dong, Haijun; Lang, Dieter; Haining, Robert L.
In: Drug Metabolism and Disposition, Vol. 29, No. 11, 2001, p. 1362-1365.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Characterization of dextromethorphan O- and N-demethylation catalyzed by highly purified recombinant human CYP2D6
AU - Yu, Aiming
AU - Dong, Haijun
AU - Lang, Dieter
AU - Haining, Robert L.
PY - 2001
Y1 - 2001
N2 - The O-demethylation of dextromethorphan to dextrorphan in humans is catalyzed primarily by cytochrome P450 2D6 (CYP2D6). However, contrary to conventional wisdom, preparations of recombinant cytochrome P450 (P450) expressed from CYP2D6*1 cDNA also appear to produce significant amounts of 3-methoxymorphinan, the N-demethylated metabolite of dextromethorphan, when assayed in vitro, We hypothesized that both pathways were intrinsic to 2D6 and here further examine the kinetics of formation using a highly purified preparation of CYP2D6 in a reconstituted lipid system. Purified CYP2D6 protein with a measured molecular weight of 55772.0 (55769.6 Da predicted) was reconstituted into an active, lipid-vesicle environment with purified rat cytochrome P450 reductase before the addition of substrate and NADPH. Reaction kinetics were followed, and apparent Michaelis-Menten constants were determined for the appearance of each metabolite by high-pressure liquid chromatography, using both UV and fluorescence detection. In a 2-min assay, purified 2D6 catalyzed the formation of dextrorphan with an apparent Km value of 1.9 ± 0.2 μM and a Vmax value of 8.5 ± 0.2 nmol/nmol of P450/min and measured simultaneously the formation of 3-methoxymorphinan with an apparent Km value of 5000 ± 700 μM and Vmax value of 176 ± 12 nmol (nmol of P450)-1 min-1. These results indicate that at least two distinct binding orientations exist for dextromethorphan within the active site of CYP2D6.
AB - The O-demethylation of dextromethorphan to dextrorphan in humans is catalyzed primarily by cytochrome P450 2D6 (CYP2D6). However, contrary to conventional wisdom, preparations of recombinant cytochrome P450 (P450) expressed from CYP2D6*1 cDNA also appear to produce significant amounts of 3-methoxymorphinan, the N-demethylated metabolite of dextromethorphan, when assayed in vitro, We hypothesized that both pathways were intrinsic to 2D6 and here further examine the kinetics of formation using a highly purified preparation of CYP2D6 in a reconstituted lipid system. Purified CYP2D6 protein with a measured molecular weight of 55772.0 (55769.6 Da predicted) was reconstituted into an active, lipid-vesicle environment with purified rat cytochrome P450 reductase before the addition of substrate and NADPH. Reaction kinetics were followed, and apparent Michaelis-Menten constants were determined for the appearance of each metabolite by high-pressure liquid chromatography, using both UV and fluorescence detection. In a 2-min assay, purified 2D6 catalyzed the formation of dextrorphan with an apparent Km value of 1.9 ± 0.2 μM and a Vmax value of 8.5 ± 0.2 nmol/nmol of P450/min and measured simultaneously the formation of 3-methoxymorphinan with an apparent Km value of 5000 ± 700 μM and Vmax value of 176 ± 12 nmol (nmol of P450)-1 min-1. These results indicate that at least two distinct binding orientations exist for dextromethorphan within the active site of CYP2D6.
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UR - http://www.scopus.com/inward/citedby.url?scp=0034771887&partnerID=8YFLogxK
M3 - Article
C2 - 11602510
AN - SCOPUS:0034771887
VL - 29
SP - 1362
EP - 1365
JO - Drug Metabolism and Disposition
JF - Drug Metabolism and Disposition
SN - 0090-9556
IS - 11
ER -