Specificity and selectivity of EP compounds as direct inhibitors of blood coagulation proteases. The relative decrease of the initial velocity of hydrolysis of specific reporter substrates by the indicated proteases is shown as a function of EP compound concentration. Data for the 6 proteases that were significantly inhibited up to 10⁻⁴M EP compound are shown as a function of increasing EP42675 (open symbols) or EP217609 (solid symbols) concentration. Data for EP217609 only are presented for the 4 proteases whose activity was insignificantly inhibited over the same EP compound concentration range. Solid and dashed lines indicate fits of EP217609 and EP42675 data, respectively, by equations for tight binding or regular competitive inhibition, which yielded values of K_I*. K_I was calculated from K_I* by dividing the latter by the factor for competitive substrate inhibition, except for the K_I* measured for thrombin, which required no correction. K_I values are tabulated in Table 2.