Amidolytic and anticoagulant activities of E149A-APC. (A) Amidolytic activity of wt-hAPC (□) and E149A-hAPC (◇) for a small chromogenic substrate (S-2366). (B) APC anticoagulant activity of E149A-hAPC (◇) compared with wt-hAPC (□) in APTT clotting assays. (C) Time course of fVa inactivation by wt-hAPC (□) and E149A-hAPC (◇). After fVa incubation with APC for the times indicated, remaining fVa activity was determined in a prothrombinase assay. (D) The effect of protein S on the inactivation of fVa by wt-hAPC (□) and E149A-hAPC (◇). (E) wt-hAPC anticoagulant activity in protein S-depleted plasma reconstituted with (■) or without (□) protein S measured by the ETP method. (F) Anticoagulant effects of wt-hAPC (□) and E149A-hAPC (◇) in protein S-depleted plasma reconstituted with protein S. Each point represents the mean plus or minus SEM of at least 3 independent experiments.