Table 3.
Kinetic parameters of horse TK1
| Substrate | KM (μM) | Vmax (μmol/min/mg) | Efficiency (Vmax/KM) | Hill coefficient |
|---|---|---|---|---|
| dThd | 0.47 ± 0.09 | 0.95 ± 0.02 | 2.02 (100)a | 0.57 |
| dUrd | 1.64 ± 0.50 | 0.81 ± 0.05 | 0.49 (25.0) | 1.0 |
| 5FdU | 1.06 ± 0.2 | 1.08 ± 0.05 | 1.02 (50.4) | 1.0 |
| AZT | 0.12 ± 0.08 | 0.53 ± 0.02 | 4.56 (225.9) | 1.0 |
| TFT | 0.72 ± 0.28 | 0.93 ± 0.02 | 1.29 (64.0) | 1.0 |
| Urd | 1511 ± 229 | 0.41 ± 0.02 | 0.00027 (0.013) | 1.0 |
| ATP | 1501 ± 287 | 3.00 ± 0.29 | 0.0020 | 1.9 |
Kinetic parameters were determined using a coupled spectrophotometric method at 21 °C. To determine the kinetic parameters for phosphate acceptors, the ATP concentration was fixed at 1 mM, and to determine the kinetic parameters for ATP, the dThd concentration was fixed at 100 μM. The KM and Vmax values were calculated by fitting the initial velocity data into the Michaelis-Menten equation. The Hill coefficient was calculated by fitting the initial velocity data into the Hill equation
aData in parentheses are relative efficiency compared with dThd (as 100%)