Michaelis-Menten kinetic parameters in microsomes from baculovirus-infected insect cells expressing CYP isoforms
| CYP isoforms | Km | Vmax | Vmax/Km |
|---|---|---|---|
| μM | pmol/min/pmol CYP | μl/min/pmol CYP | |
| CYP1A2 | 100.8 ± 4.23 | 12.6 ± 0.91 | 0.125 ± 0.009 |
| CYP2C19 | 17.1 ± 0.29 | 3.4 ± 0.20 | 0.201 ± 0.011 |
| CYP2D6 | 3.75 ± 0.04 | 2.3 ± 0.09 | 0.621 ± 0.018 |
| CYP3A4 + cytochromeb5 | 43.7 ± 4.05 | 17.6 ± 0.41 | 0.405 ± 0.028 |
The concentration of microsomes was 5 (for CYP3A4), 10 (for CYP1A2), and 20 (for CYP2C19 and 2D6) pmol CYP/ml. Microsomes were incubated with azelastine (1–400 μM) for 30 min, and the rate of azelastine N-demethylation was determined by HPLC. Data are the averages (±S.D.) of tripricate determinations.