Activity | P450 | High-Affinity Activity | Low-Affinity Activity | |||||
---|---|---|---|---|---|---|---|---|
Km | Vmax | Vmax/Km | Km | Vmax | Vmax/Km | ΣVmax/Km | ||
μM | pmol/min per pmol P450 | μl/min per nmol P450 | μM | pmol/min per pmol P450 | μl/min per nmol P450 | |||
(+)-M1 | CYP2D15 | 5.5 | 1.0 | 182 | 66 | 2.1 | 32 | 214 |
CYP2B11 | 173 | 0.3 | 1.7 | |||||
(−)-M1 | CYP2D15 | 3.0 | 0.12 | 40 | 59 | 1.3 | 22 | 62 |
CYP2B11 | 445 | 0.18 | 0.4 | |||||
(+)-M2 | CYP2B11 | 10.4 | 0.5 | 48 | 430 | 1.5 | 3.5 | 51.5 |
CYP2D15 | 474 | 0.6 | 1.3 | |||||
CYP2C21 | 30 | 0.4 | 13 | |||||
CYP2C41 | 8.5 | 1.1 | 130 | |||||
CYP3A12 | 23 | 1.5 | 65 | |||||
(−)-M2 | CYP2B11 | 7.2 | 0.2 | 28 | 765 | 1.9 | 2.5 | 30.5 |
CYP2D15 | 351 | 0.6 | 1.7 | |||||
CYP2C21 | 68.5 | 0.3 | 4.4 | |||||
CYP2C41 | 61 | 0.8 | 13 | |||||
CYP3A12 | 55 | 0.4 | 7.3 |
The data points used for fitting were the average of three independent experiments performed in duplicate (data points shown in Fig. 5 with the curves of best fit). Fitted parameters included Km and Vmax, while intrinsic clearance (Vmax/Km) values were calculated. Data for (+)-M1 and (−)-M1 formation by CYP2D15 were best fit by a two-enzyme model. Kinetic parameters for high- and low-affinity activities, as well as the sum of the high and low intrinsic clearance values (ΣVmax/Km), are given.