Kinetic parameters for diclofenac hydroxylation activities of wild-type and variant CYP2C9s
Data are presented as the mean ± S.D. of three to four different expression experiments.
Recombinant Enzymes (Amino Acid Alteration) | Km | Vmax | Clearance (Vmax/Km) |
|---|---|---|---|
| μM | pmol/min/pmol P450 | μl/min/pmol P450 | |
| CYP2C9.1 (wild type)a | 1.8 ± 0.2 | 76.2 ± 6.5 | 43.6 ± 7.2 |
| CYP2C9.3 (I359L) | 5.3 ± 0.5*** | 84.9 ± 12.8 | 16.1 ± 2.3*** |
| CYP2C9.13 (L90P) | 7.0 ± 0.8*** | 14.3 ± 3.2*** | 2.1 ± 0.6*** |
| CYP2C9.26 (T130R) | 3.1 ± 0.2** | 32.0 ± 4.9*** | 10.5 ± 2.2*** |
| CYP2C9.28 (Q214L) | 7.3 ± 0.5*** | 84.6 ± 10.3 | 11.6 ± 1.6*** |
| CYP2C9.30 (A477T) | 7.7 ± 0.3*** | 63.7 ± 9.1 | 8.3 ± 1.3*** |
| CYP2C9.1 (wild type)b | 3.4 ± 0.2 | 79.8 ± 6.6 | 23.4 ± 0.8 |
| CYP2C9.33 (R132Q)b | 1.8 ± 0.1 | 7.8 ± 0.4 | 4.2 ± 0.3 |
| CYP2C9.34 (R335Q)b | 3.0 ± 0.1 | 65.4 ± 2.1 | 22.0 ± 0.1 |
| BD Gentest CYP2C9.1 | 2.7 | 30.6 | 11.5 |
| BD Gentest human liver microsomes | 5.3 | 5.4 | 1.0 |
↵a Because the substrate consumption at the two lowest substrate concentrations (1 and 2.5 μM) was greater than 20%, these two points were omitted from the kinetic parameter estimation. However, this had no effect on the estimate of Vmax and a very minor effect on the derived Km (1.7 vs. 1.8 μM).
↵b Previous data on CYP2C9.1, CYP2C9.33, and CYP2C9.34 (Yin et al., 2008) are cited.
↵** P < 0.01 vs. wild type. One-way ANOVA with a post hoc Dunnett multiple comparisons test among CYP2C9.1 and five variants tested in the present study.
↵*** P < 0.001 vs. wild type.