TABLE 1.
Effects of alternate substrates on nicotine Δ5′(1′)iminium ion-mediated inactivation of CYP2A6 and CYP2A13
Enzymes were incubated with nicotine Δ5′(1′)iminium ion (200 μM for 60 min with CYP2A6; 50 μM for 20 min with CYP2A13) at 30°C, in the presence of alternate substrate. Coumarin 7-hydroxylation activity was determined in a secondary reaction as described under Materials and Methods. The values reported are the mean ± S.D. for three independent experiments.
| Alternate Substrate | Ratio of Iminium Ion/Alternate Substrate | Percentage Activity Remaining | |
|---|---|---|---|
| CYP2A6 | 1:0 | 46 ± 7 | |
| CYP2A6 | NNN, 10 μM | 20:1 | 50 ± 3 |
| CYP2A6 | NNN, 50 μM | 4:1 | 111 ± 13 |
| CYP2A13 | 1:0 | 38 ± 1 | |
| CYP2A13 | Cotinine, 50 μM | 1:1 | 48 ± 4 |
| CYP2A13 | Cotinine, 400 μM | 1:8 | 69 ± 2 |