Prethrombin-1 activation in the presence or absence of PCPS. The initial velocity of thrombin generation was determined at increasing concentrations of prethrombin-1 in the presence (A) or absence (B) of 50 μM PCPS and 3 μM DAPA with 0.1 nM pt-FXa and 20 nM pt-rFV (● or ○), pt-rFV-QQ (▲ or △), or pt-rFVa (■ or □). The lines were drawn after analysis of all datasets to a rectangular hyperbola, and the fitted kinetic constants can be found in Table 1. The data are representative of 2 similar experiments.