TABLE 2

Steady-state kinetics analysis: IFA metabolism catalyzed by P450s 2B1, 2B4, and 2B5

4-Hydroxylation N-Dechloroethylation
P450 KmVmaxVmax/KmKmVmaxVmax/Km % N-deCla
mM mol/min/mol mol/min/mol mM mol/min/mol mol/min/mol
P450 P450/mM P450 P450/mM
2B1b 1.73 ± 0.44 13.2 ± 1.1 7.9 ± 1.8 1.87 ± 0.72 14.7 ± 1.7 8.8 ± 3.4 52.7 ± 2.4
2B4c 4.78 ± 0.63 3.1 ± 0.1 0.65 ± 0.06 7.64 ± 0.54 3.1 ± 0.6 0.41 ± 0.05 50.1 ± 4.0
2B5c 2.52 ± 0.31 0.95 ± 0.07 0.38 ± 0.08 N.D. 0 0 0

  • N.D., not determined; catalytic activity at or below limit of detection.

  • ↵ a N-dechloroethylation as a percentage of total metabolism at Vmax.

  • ↵ b Data are based on n = 4 independent experiments.

  • ↵ c Data are based on n = 2 independent experiments.