TABLE 4.
Kinetic parameters of dihydropyrimidine dehydrogenase (DPD) variants in 5-FU metabolism.
| Variants | K m (μM) | V max (pmol/minute/DPD unit) | CL int (V max /K m ) (μl/minute/DPD unit) | % of Wild-type CL int |
|---|---|---|---|---|
| Wild-type | 1.60 ± 0.10 | 31.56 ± 1.00 | 19.77 ± 0.66 | 100.00 |
| H25R | 0.75 ± 0.04 | 12.53 ± 0.23 | 16.82 ± 0.83 | 85.10 |
| C29R | 1.57 ± 0.21 | 11.15 ± 0.66 | 7.14 ± 0.53 | 36.14 |
| M77V | 0.77 ± 0.06 | 10.15 ± 0.47 | 13.20 ± 0.85 | 66.79 |
| Y109N | 1.12 ± 0.13 | 11.19 ± 0.33 | 10.11 ± 1.11 | 51.17 |
| N151D | 2.81 ± 3.11 | 21.73 ± 7.27 | 13.25 ± 7.69 | 67.03 |
| M166V | 1.03 ± 0.09 | 12.62 ± 1.21 | 12.20 ± 0.18 | 61.74 |
| S175L | 0.62 ± 0.04 | 13.61 ± 0.70 | 21.88 ± 1.06 | 110.66 |
| A191V | 1.11 ± 0.04 | 16.10 ± 1.06 | 14.49 ± 0.94 | 73.32 |
| I245F | 1.94 ± 0.19 | 25.70 ± 1.27 | 13.36 ± 1.36 | 67.57 |
| D291N | 1.08 ± 0.22 | 22.77 ± 2.33 | 21.35 ± 2.60 | 108.00 |
| T298M | 1.23 ± 0.14 | 16.12 ± 0.81 | 13.16 ± 0.81 | 66.58 |
| Y304H | 2.22 ± 0.24 | 8.79 ± 0.84 | 3.97 ± 0.12 | 20.07 |
| V313L | 1.46 ± 0.30 | 23.46 ± 2.86 | 16.35 ± 1.80 | 82.73 |
| M321I | 0.96 ± 0.15 | 11.99 ± 0.54 | 12.62 ± 1.55 | 63.83 |
| V335M | 1.27 ± 0.01 | 13.04 ± 0.47 | 10.25 ± 0.46 | 51.84 |
| C354Y | 0.99 ± 0.08 | 15.35 ± 0.34 | 15.61 ± 0.95 | 78.96 |
| G366A | 1.62 ± 0.18 | 17.11 ± 1.64 | 10.61 ± 0.40 | 53.66 |
| A380V | 0.56 ± 0.04 | 8.62 ± 0.39 | 15.48 ± 0.52 | 78.30 |
| K384E | 0.80 ± 0.10 | 18.49 ± 0.65 | 23.29 ± 2.50 | 117.80 |
| V434L | 1.15 ± 0.04 | 14.94 ± 0.99 | 12.94 ± 0.50 | 65.45 |
| F438V | 0.40 ± 0.01 | 0.86 ± 0.04 | 2.15 ± 0.17 | 10.87 |
| V515I | 1.22 ± 0.08 | 25.31 ± 1.67 | 20.81 ± 0.14 | 105.28 |
| F524L | 1.18 ± 0.09 | 35.15 ± 1.15 | 29.80 ± 1.73 | 150.77 |
| I528V | 1.22 ± 0.18 | 38.44 ± 2.65 | 31.78 ± 2.86 | 160.76 |
| I543V | 0.99 ± 0.35 | 13.89 ± 2.11 | 14.71 ± 2.60 | 74.41 |
| I560V | 1.98 ± 0.13 | 36.86 ± 1.30 | 18.63 ± 0.72 | 94.22 |
| I560S | 1.28 ± 0.43 | 26.68 ± 4.42 | 21.70 ± 4.37 | 109.75 |
| R592W | 2.49 ± 0.28 | 2.09 ± 0.08 | 0.84 ± 0.08 | 4.27 |
| Q604L | 1.12 ± 0.11 | 23.99 ± 0.34 | 21.50 ± 1.82 | 108.74 |
| V732I | 1.14 ± 0.06 | 27.36 ± 1.82 | 23.93 ± 1.22 | 121.06 |
| V738L | 1.36 ± 0.19 | 25.67 ± 1.51 | 19.04 ± 1.52 | 96.30 |
| G748D | 2.25 ± 1.31 | 2.38 ± 0.27 | 1.24 ± 0.45 | 6.26 |
| T768K | 1.69 ± 0.42 | 14.22 ± 1.56 | 8.62 ± 1.23 | 43.58 |
| H807R | 1.06 ± 0.26 | 10.60 ± 1.56 | 10.19 ± 0.92 | 51.54 |
| V826M | 0.83 ± 0.14 | 11.46 ± 0.61 | 14.05 ± 1.60 | 71.08 |
| I843T | 1.00 ± 0.11 | 28.28 ± 1.63 | 28.25 ± 1.58 | 142.92 |
| R886H | 0.96 ± 0.09 | 27.57 ± 0.72 | 28.82 ± 1.99 | 145.81 |
| N893S | 1.27 ± 0.13 | 18.27 ± 0.54 | 14.46 ± 1.33 | 73.15 |
| S939N | 1.00 ± 0.22 | 28.68 ± 3.09 | 29.38 ± 3.93 | 148.64 |
| D949V | 0.85 ± 0.08 | 30.99 ± 0.37 | 36.77 ± 3.19 | 186.01 |
| T990I | 1.77 ± 0.15 | 12.81 ± 0.55 | 7.29 ± 0.89 | 36.86 |
Data represent the mean ± standard deviation of three independent catalytic assays. The kinetic parameters of R353C, DPYD*2A, and G926V could not be determined because enzymatic activity was not detected at the highest substrate concentration used in the assay (200 μM 5-FU). K m , Michaelis constant; V max , maximum velocity; CL int , intrinsic clearance.