Sand fly salivary protein with antithrombotic, and anti-complement (alternative pathway) activities (PubMed:22796577, PubMed:28912782). Is a slow, tight, non-competitive, and reversible inhibitor of factor Xa (FXa, F10) (PubMed:22796577). Is specific for FXa (Kd=3.86 nM) and does not interact with non-activated FX, or all other enzymes tested (PubMed:22796577). In addition, it blocks prothrombinase and increases both prothrombin time and activated partial thromboplastin time (PubMed:22796577). It also prevents protease-activated receptor 2 (F2RL1, PAR2) activation by FXa (PubMed:22796577). In vivo, it abrogates edema formation triggered by injection of FXa in the paw of mice (PubMed:22796577). Moreover, it prevents FeCl3-induced carotid artery thrombus formation and prolongs activated partial thromboplastin time ex vivo, implying that it works as an anticoagulant in vivo (PubMed:22796577). It also inhibits the early steps of the alternative pathway of complement by direct binding to the proconvertase C3b-B complex, by inhibiting activation of factor B and consequently the formation of the C3 convertase (PubMed:28912782). Interacts with factor Xa (PubMed:22796577). Interacts with complement proconvertase C3b-B complex (PubMed:28912782). Expressed in salivary glands.