Kinetic analysis of 7-ethoxyresorufin O-deethylation by recombinant human P450 enzymes and by human liver microsomes
| Enzymes | 7-EthoxyresorufinO-Deethylation | |
|---|---|---|
| Km (μM) | Vmax (nmol/min/nmol P450) | |
| Human enzymes | ||
| CYP1A1 | 2.8 ± 0.5 | 18.2 ± 1.2 |
| CYP1A2 | 3.0 ± 0.6 | 0.23 ± 0.02 |
| CYP1B1 | 1.0 ± 0.2 | 1.33 ± 0.06 |
| Liver chromosomes | 2.9 ± 0.5 | 0.21 ± 0.01 |
| Rat enzymes | ||
| CYP1A1 | 3.3 ± 0.6 | 11.4 ± 0.9 |
| CYP1A2 | 2.3 ± 0.4 | 0.83 ± 0.05 |
Kinetic analysis was determined using P450 concentrations of 5 nM for human CYP1A1 and 1B1 and rat CYP1A1 and 1A2 and 20 nM for human CYP1A2 and liver microsomes. Values are means ± SEM of duplicate determinations at substrate concentrations between 2∼16 μM (using a nonlinear kinetic analysis).