Inhibition Assay: Assays for slow-onset inhibitors were carried out by adding 1 nM PaMTIP into reaction mixtures at 25 °C. containing 100 mM Hepes, pH 7.4, 100 mM phosphate, pH 7.4, 2 mM MTI, 5 mM DTT, 0.5 unit of xanthine oxidase and variable inhibitor concentration. Inhibitors were present at >10 times the enzyme concentration. Assays for MTA inhibition used 200 μM MTI. Controls having no enzyme and no inhibitor were included in all of the inhibition assays. Slow-onset inhibitors display a second phase of tighter binding after reaching a thermodynamic equilibrium with the enzyme. The equilibrium constant for the second binding phase is indicated as Ki*.
Inhibition Assay: Assays for slow-onset inhibitors were carried out by adding 1 nM PaMTIP into reaction mixtures at 25 °C. containing 100 mM Hepes, pH 7.4, 100 mM phosphate, pH 7.4, 2 mM MTI, 5 mM DTT, 0.5 unit of xanthine oxidase and variable inhibitor concentration. Inhibitors were present at >10 times the enzyme concentration. Assays for MTA inhibition used 200 μM MTI. Controls having no enzyme and no inhibitor were included in all of the inhibition assays. Ki is the inhibition constant.