TABLE 3

Kinetic parameters for theophylline metabolism by recombinant CYP1As and CYP2As

Data are mean ± S.D. of three independent experiments.




Km

Vmax

Vmax/Km
mM pmol/min/pmol P450 nl/min/pmol P450
8-Hydroxylation (1,3-DMU formation)
    CYP1A1 3.9 ± 0.1 5.1 ± 0.2 1.3 ± 0.1
    CYP1A2 0.6 ± 0.0 24.4 ± 2.5 40.0 ± 4.0
    CYP2A6 8.7 ± 0.4a,b 7.4 ± 0.3a,b 0.9 ± 0.0a,b
    CYP2A13 2.5 ± 0.1a,b 10.3 ± 0.4a,b 4.1 ± 0.2a,b
3-Demethylation (1-MX formation)
    CYP1A1 11.1 ± 1.5 1.7 ± 0.2 0.2 ± 0.0
    CYP1A2 0.6 ± 0.1 1.0 ± 0.2 1.8 ± 0.3
    CYP2A6 N.D. N.D. N.D.
    CYP2A13 1.4 ± 0.2a,b 0.2 ± 0.0a,b 0.2 ± 0.0b
1-Demethylation (3-MX formation)
    CYP1A1 N.D. N.D. N.D.
    CYP1A2 0.6 ± 0.1 1.1 ± 0.2 1.8 ± 0.3
    CYP2A6 N.D. N.D. N.D.
    CYP2A13
N.D.
N.D.
N.D.
  • N.D., not detected.

  • a P < 0.005 compared with CYP1A1.

  • b P < 0.005 compared with CYP1A2.