TABLE 2.

The effect of CYP2E1 and CPR on the apparent K_M and k_cat of CYP2B4 for the metabolism of BNZ

The rate of BNZ N-demethylation by CYP2B4 was determined as described under Materials and Methods. All samples contained 0.50 μM CYP2B4 and increasing concentrations of BNZ. The “control” sample contained equal concentrations of CPR and CYP2B4, “plus CYP2E1” contained 2 μM CYP2E1 in addition to the components in the “control” sample, “plus CYP2E1 and excess CPR” contained 2.5 μM CPR in addition to the components in the “plus CYP2E1” sample and, “plus saturating CPR” contained the same components as the “control” sample except for the addition of 2.5 μM CPR. The kinetic values given here were derived from data plotted in Fig. 6.

	CYP2B4
	Control	Plus CYP2E1	Plus Saturating CPR	Plus CYP2E1 and Saturating CPR
KM (mM)	0.075 ± 0.010	0.60 ± 0.13	0.060 ± 0.012	0.17 ± 0.051
kcat (min–1)	32 ± 0.78	33 ± 3.7	35 ± 1.6	30 ± 3.0