Table 1

Kinetic parameters for 7EFC O-deethylation: cDNA-expressed enzymes

EnzymeKM Vmax
μM pmol product/pmol P450/min
CYP1A2<0.11.7
CYP1A11.812
CYP2B62.92.5
CYP2C19171.6
CYP2C9350.4
CYP2E1461.2
CYP2A6>500.05 (activity at 20 μM)

7EFC O-deethylase activity was assayed as described in Materials and Methods. Kinetic parameters were calculated by nonlinear regression using GraFit 3.0 software. The 7EFC concentrations were 6.25–1,600 nM (CYP1A2), 0.25–8 μM (CYP1A1), 0.5–16 μM (CYP2B6), 0.63–20 μM (CYP2C9 and CYP2C19), and 20–200 μM (CYP2E1).