TABLE 2.
CYP2A13-catalyzed [3H]cotinine and [3H]nicotine Δ5′(1′)iminium ion metabolism
CYP2A13 (25 pmol) was incubated with the indicated substrates (4 μCi/nmol) at 30°C. Aliquots were removed from each sample at the indicated times and analyzed on HPLC system II. The values are the mean ± S.D. for four independent experiments.
| Substrate (5 μM) | Time | Ratio of Products |
Percentage Total Radioactivity Cotinine | |
|---|---|---|---|---|
| cis-3HCOT/trans-3HCOT | 3HCOTa/ 5HCOT | |||
| min | ||||
| [3H]nicotine Δ5′(1′)iminium ion | 1 | 0.5 ± 0.08b | 4.5 ± 0.3b | 15 ± 3 |
| 2.5 | 0.4 ± 0.05 | 2.6 ± 0.3 | 25 ± 3 | |
| 5 | 0.4 ± 0.02 | 1.9 ± 0.2 | 37 ± 4 | |
| 10 | 0.3 ± 0.02b | 1.1 ± 0.1b | 47 ± 3 | |
| [3H]cotinine | 1 | No cis-3HCOT | N.D. | N.D. |
| 2.5 | No cis-3HCOT | 0.2 ± 0.1 | 93 ± 3 | |
| 5 | No cis-3HCOT | 0.3 ± 0.1 | 94 ± 2 | |
| 10 | No cis-3HCOT | 0.2 ± 0.1 | 94 ± 1 | |
N.D., not detected.
a
cis and trans isomers combined.
b
Values significantly different by paired one-tailed t-test; P < 0.005