TABLE 1

Kinetic analysis of cotinine-N-oxide formation by P450 enzymes.

Data are expressed as the mean ± S.D. of three independent experiments. Cotinine concentrations of 0.005–10 mM were used for kinetic analysis.

P450 EnzymeKMVmaxVmax/KM
(uM)(pmol • min-1 • mg-1)a(nL • min-1 • mg-1)a
2A6390 ± 8717 ± 1.544 ± 7.6
2B6810 ± 2416 ± 0.0122 ± 6.9
2C19405 ± 1915 ± 1.642 ± 19
2E1>10 mMNDND
3A4>10 mMNDND
HLMb550 ± 49587 ± 261070 ± 8.4
  • ND, not determined.

  • aThe Vmax was calculated per total microsomal protein levels after normalization based on microsomal P450 expression levels as determined by western blot analysis.

  • bPooled human liver microsomes from 20 individuals.