Prothrombinase containing FVL is less susceptible to inhibition by TFPIα. Various amounts of (A) TFPIα or (B) LIKTKRKRKK were incubated with 0.5 nM FV810 (□) or FVL810 (●), 20 μM PC:PE:PS, and 3 μM DAPA. Reactions were initiated with mixtures of 1.4 μM prothrombin and 5 nM FXa. The prothrombinase activity ± SD is reported as percent of control from 3 sets of experiments.