Table 1

Kinetic parameters of recombinant human TK1 with boronated dThds as substrates

CompoundKm (μmol/L)kcat (s−1)kcat/Km% to dThdIC50 (μmol/L)0.5 μmol/L dThdIC50 (μmol/L)5 μmol/L dThd
1 5.1 ± 1.20.32 ± 0.1127.4 ± 3.821.1 ± 3.235.2 ± 4.9
2 26.1 ± 4.20.72 ± 0.0813.1 ± 3.8
3 8.5 ± 1.80.16 ± 0.028.5 ± 0.5
4 3.7 ± 0.50.22 ± 0.0326.7 ± 0.614.0 ± 6.133.9 ± 8.6
5 16.7 ± 0.10.18 ± 0.025.2 ± 1.9
6 36.5 ± 8.40.12 ± 0.011.8 ± 0.98.1 ± 2.016.7 ± 2.1
7 6.1 ± 2.70.27 ± 0.0031.9 ± 14.124.2 ± 1.937.0 ± 3.1
8 10.3 ± 2.00.29 ± 0.0616.4 ± 0.2
9 15.5 ± 7.20.31 ± 0.0114.4 ± 6.0
10 3.4 ± 0.60.21 ± 0.0235.8 ± 2.69.3 ± 3.822.0 ± 5.1
11 7.6 ± 0.50.33 ± 0.0224.9 ± 0.6
12 28.4 ± 7.40.08 ± 0.001.7 ± 0.57.2 ± 2.119.2 ± 4.1
9 *71.8 ± 6.10.93 ± 0.140.07 ± 0.01
12 *90.0 ± 6.20.56 ± 0.080.04 ± 0.00
  • NOTE. The parameters were calculated using Michaelis-Menten equation. The concentration of compounds 1-12 ranged from 1 to 100 μmol/L. The kcat values were calculated using the equation Vmax = kcat × [E], where [E] is the total enzyme concentration based on one active site/monomer. Under the same experimental conditions, the kinetic parameters for dThd were Km = 2.4 ± 0.8 μmol/L and kcat = 0.6 ± 0.2 s−1, data represent the mean ± SDs of three independent experiments. The IC50 is defined as the concentrations of a compound required to inhibit the TK1 phosphorylating of dThd by 50%. Data represent the mean ± SDs of at least three independent experiments, each performed in duplicate.

  • * Kinetic parameter values at high concentrations of the compounds.