The Ki values and inhibition types of endogenous compounds for the CYP2A6 enzyme activities
Data generated by nonlinear regression analysis are expressed as mean ± S.E. of duplicate determinations.
Inhibitor | Coumarin 7-Hydroxylation | Cotinine 3′-Hydroxylation | Cotinine Formation from Nicotine | Nicotine-Δ5′(1′)-iminium Ion Formation from Nicotine | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ki | Type of Inhibition | Ki | Type of Inhibition | Ki | Type of Inhibition | Ki | Type of Inhibition | |||||
| μM | μM | μM | μM | |||||||||
| Tryptophan | — | — | ||||||||||
| Tryptamine | 0.2 ± 0.1 | Competitive | 0.2 ± 0.0 | Competitive | 0.7 ± 0.1 | Competitive | 0.3 ± 0.0 | Competitive | ||||
| Serotonin | 252 ± 47 | Competitive | 167 ± 14 | Competitive | 272 ± 74 | Noncompetitive | 316 ± 48 | Competitive | ||||
| Melatonin | — | — | — | — | ||||||||
| Tyrosine | — | — | — | — | ||||||||
| l-DOPA | — | — | — | — | ||||||||
| Dopamine | 49 ± 2 | Competitive | 22 ± 5 | Competitive | 11 ± 3 | Uncompetitive | 66 ± 21 | Competitive | ||||
| Noradrenaline | — | — | 54 ± 3 | Uncompetitive | ||||||||
| Adrenaline | — | — | 81 ± 6 | Uncompetitive | ||||||||
| Histamine | 428 ± 152 | Competitive | 359 ± 86 | Competitive | — | 209 ± 47 | Competitive | |||||
| Progesterone | — | — | — | — | ||||||||
| Corticosterone | — | — | 36 ± 19 | Uncompetitive | — | |||||||
| Androstenedione | — | — | 149 ± 25 | Mixed | ||||||||
| Testosterone | — | — | 60 ± 10 | Uncompetitive | ||||||||
| Androstanediol | — | — | — | — | ||||||||
| Estrone | — | — | 3.8 ± 0.9 | Uncompetitive | — | |||||||
| Estradiol | — | — | 0.9 ± 0.5 | Uncompetitive | — | |||||||
| Estriol | — |
| — |
| 0.6 ± 0.1 | Uncompetitive |
|
| ||||
—, not applicable.