This is the first member of the serine protease family that has strong anticoagulant activity and lacks enzymatic activity. It inhibits activities of three blood coagulation complexes: (1) prothrombinase complex (composed of blood coagulation factors Va and Xa (F5 and F10)) (IC(50)=164.1 nM), (2) intrinsic tenase complex (composed of factors VIIIa and IXa (F8 and F9)), and (3) extrinsic tenase complex (composed of tissue factor and factor VIIa (F7)). The toxin has also been observed to bind prothrombin, factor FVa, non-activated and activated forms of factors FVII (F7) (FVII and FVIIa), factor FVIIIa (F8), factors FIX and FIXa (F9) and factors FX and FXa (F10). The toxin inhibits the activity of the intrinsic tenase complex mainly by competing with FIXa (F9) for binding to FVIIIa (F8). Expressed by the venom gland. N-glycosylated. The toxin exists in multiple glycoforms. This first serine protease family member whose strong anticoagulant activity is not proteolytic activity-dependent represents an original molecular platform to develop innovative anticoagulant substances by targeting FVIIIa. It does not hydrolysis fibrinogen, prothrombin, FIX, FX and protein C (PubMed:30235482). It does not induce platelet aggregation or agglutination (PubMed:30235482). It does not bind to platelet phospholipids (PubMed:30235482). It does not bind to factor FXI and FXIa, FXII and FXIIa, kallikrein and thrombin (PubMed:30235482). Belongs to the peptidase S1 family. Snake venom subfamily. Lacks the canonical catalytic triad. Two of the three residues necessary for catalytic activity are mutated. Arg-67 stands instead of an His and at position Asn-206 stands instead of a Ser. As a result, the protein is not proteolytically active.