Kinetics measurements of PtpB inhibitors.

<p>Lineweaver-Burk double-reciprocal plots representing inhibitory profiles of compounds KuwE, PirIII, Ega1, 6016, Ac3 and ∆3 against PtpB. Kinetic experiments were conducted in the presence of increasing concentrations of inhibitors: 0 µM (), 1 µM (), 2 µM (), 3 µM (), 6 µM (), 10 µM (), 20 µM (), 25 µM (), 30 µM (), 35 µM (), 40 µM (), 45 µM (); <i>p</i>NPP was used as substrate in all experiments. For KuwE, Ac3 and 6016, all lines converged at the <i>y</i>-axis (1/<i>V</i>_max), whereas the slope (K_Mapp/<i>V</i>_max) and <i>x</i>-axis interception (1/<i>K</i>_Mapp) varies according to the inhibitor concentration; the constant value of <i>V</i>_max and the increased values of <i>K</i>_Mapp are consistent with a competitive inhibition mechanism. For PirIII, Ega1 and Δ3, all lines converge at the <i>x</i>-axis (1/<i>K</i>_Mapp) and the <i>y</i>-axis interception (1/<i>V</i>_max) varies as a function of the inhibitor concentration; the constant value of <i>K</i>_Mapp and the increased values of <i>V</i>_max indicate that these compounds are noncompetitive inhibitors.