Table 3

Kinetic parameter estimates for flurbiprofen hydroxylation, naproxen demethylation, and piroxicam hydroxylation in the presence of dapsone

SubstrateKm(S.E.)Vmax (S.E.)KB(S.E.)α (S.E.)β (S.E.)R2
μM pmol/min/pmol P450 μM
(S)-Flurbiprofen26.5  (3.4)12.2  (0.5)17.6  (3.6)0.3  (0.06)1.7  (0.1)0.99
(S)-Naproxen593  (128)16.2  (1.6)68.7  (23)0.1  (0.04)2.4  (0.3)0.99
Piroxicam110  (17.1)0.06  (0.003)164  (77)0.2  (0.1)4.0  (0.3)0.99

Data were fit to the two-site model (eq. 3).

  • KB, the binding constant for the effector; α, the change in Km resulting from effector binding; and β, and the change in Vmax resulting from effector binding. An α or β value = 1 indicates no change in Km or Vmax, respectively.