TABLE 5

Kinetic parameters for 5-FU formation from racemic FT mediated by wild-type CYP2A6 and its variants

The kinetic parameters were calculated by nonlinear regression analysis. Each kinetic value represents the estimated value ± S.E.

Recombinant Enzyme (Amino Acid Alteration)Kinetic Parameters
VmaxKmCLintFold Changed
pmol/min per pmol CYP2A6mMnl/min per pmol CYP2A6
CYP2A6.1 (wild-type)12 ± 00.29 ± 0.01401.0
CYP2A6.7 (I471T)1.2 ± 0.0**0.43 ± 0.02**2.70.068
CYP2A6.8 (R485L)7.8 ± 0.2**0.58 ± 0.02**140.34
CYP2A6.10 (I471T and R485L)0.46 ± 0.03**0.86 ± 0.10**0.540.013
CYP2A6.11 (S224P)5.9 ± 0.2**0.79 ± 0.04**7.50.19
HLMsa679 ± 49b0.27 ± 0.022.6cN.A.
786 ± 56b3.7 ± 0.50.21cN.A.

  • N.A., not available.

  • ↵a The conversion of racemic FT to 5-FU followed biphasic kinetics in HLMs.

  • ↵b pmol/min per mg protein.

  • ↵c μl/min per mg protein.

  • ↵d The ratio of CLint (Vmax/Km) in each CYP2A6 variant to that in CYP2A6.1.

  • ↵** P < 0.01 versus wild-type enzyme.