TABLE 1

Kinetic parameters for 10 catalytic reactions using seven substrates by CYP3A4.1, CYP3A4.16, and CYP3A4.18

Data are represented by mean ± S.D. of three different expression experiments.

KmVmaxIntrinsic Clearance (Vmax/Km)Ks
μMpmol/min/pmol P450μl/min/pmol P450μM
MDZ 1′-hydroxylation
    CYP3A4.11.9 ± 0.128.1 ± 2.814.8 ± 1.5407 ± 32
    CYP3A4.162.6 ± 0.1***15.0 ± 3.5**5.8 ± 1.7***986 ± 302*
    CYP3A4.182.0 ± 0.117.5 ± 3.2*8.8 ± 1.6**713 ± 168
MDZ 4-hydroxylation
    CYP3A4.123.1 ± 5.212.9 ± 0.10.58 ± 0.14
    CYP3A4.1651.5 ± 3.5***11.7 ± 1.40.23 ± 0.04*
    CYP3A4.1822.3 ± 3.59.2 ± 2.0*0.42 ± 0.11
CBZ epoxidationa
    CYP3A4.121.9 ± 5.2 (Km1)15.5 ± 2.50.095 ± 0.018
165 ± 15 (Km2)
    CYP3A4.1648.0 ± 3.7*** (Km1)11.0 ± 1.00.020 ± 0.008***
603 ± 204** (Km2)
    CYP3A4.1820.0 ± 2.7 (Km1)15.7 ± 4.50.090 ± 0.011
172 ± 32 (Km2)
ATV 2-hydroxylation
    CYP3A4.124.2 ± 7.66.6 ± 1.10.29 ± 0.08
    CYP3A4.1687.4 ± 22.6**8.2 ± 1.90.10 ± 0.02*
    CYP3A4.1820.2 ± 6.83.8 ± 1.30.20 ± 0.11
ATV 4-hydroxylation
    CYP3A4.119.6 ± 4.016.1 ± 5.00.84 ± 0.29
    CYP3A4.1665.4 ± 19.3**8.4 ± 1.40.14 ± 0.05*
    CYP3A4.1816.1 ± 3.411.1 ± 4.20.71 ± 0.31
PTX 3′-p-hydroxylation
    CYP3A4.12.9 ± 0.10.55 ± 0.060.19 ± 0.03
    CYP3A4.1612.9 ± 2.4***0.55 ± 0.130.04 ± 0.02***
    CYP3A4.182.7 ± 0.10.24 ± 0.07**0.09 ± 0.03**
DTX t-butyl hydroxylation
    CYP3A4.12.5 ± 0.10.38 ± 0.010.16 ± 0.01
    CYP3A4.161.8 ± 0.2**0.26 ± 0.03**0.14 ± 0.01
    CYP3A4.182.3 ± 0.20.24 ± 0.04**0.10 ± 0.03*
IRN oxidation to NPC
    CYP3A4.119.3 ± 2.71.4 ± 0.20.07 ± 0.02
    CYP3A4.1634.0 ± 2.9**0.9 ± 0.40.03 ± 0.01*
    CYP3A4.1819.7 ± 2.80.7 ± 0.1*0.04 ± 0.01*
TFN t-butyl hydroxylation
    CYP3A4.13.4 ± 0.33.4 ± 0.61.0 ± 0.2218 ± 5
    CYP3A4.163.5 ± 0.52.1 ± 0.1*0.6 ± 0.1*51 ± 8
    CYP3A4.186.0 ± 1.2*3.1 ± 0.50.5 ± 0.1*311 ± 131
TFN N -demethylationb
    CYP3A4.12.4 ± 0.52.2 ± 0.40.95 ± 0.25629 ± 244
    CYP3A4.162.1 ± 0.21.5 ± 0.30.72 ± 0.1292 ± 8
    CYP3A4.183.4 ± 0.3*1.9 ± 0.20.57 ± 0.10

  • ↵* p < 0.05,

  • ↵** p < 0.01, and

  • ↵*** p < 0.001 versus the wild-type (Dunnett's multiple comparison test).

  • ↵a For CBZ epoxidation, Km1 and Km2, Vmax2, and intrinsic clearance (Vmax2/Km2) values are indicated in each column.

  • ↵b For TFN N-demethylation, kinetic profile of CYP3A4.18 was better fitted to the Michaelis-Menten model than to the substrate inhibition model.