Venom serine protease that converts factor V (F5) to the active form Va in the presence of calcium ions and phospholipids. It cleaves the Arg(1545)-Ser(1546) linkage in the human factor V molecule. Has hydrolytic activities against BAEE (1.2 U/mg), TAME, and Pro-Phe-Arg-MCA (4.9 U/mg). Shows coagulant activity. Fully activates human clotting factor V by a single cleavage at the 1545-Trp-Tyr-Leu-Arg-|-Ser-Asn-Asn-Gly-1552 bond. Cattle, but not rabbit, factor V is cleaved, and no other proteins of the clotting system are attacked. Esterase activity is observed on Bz-Arg-OEt and Tos-Arg-OMe, and amidase activity on Phe-pipecolyl-Arg-NHPhNO2. Inhibited by D-Phe-Pro-Arg-chloromethyl ketone (FPRCK) (98%), PMSF (93%), benzamidine (67%), and diisopropylfluorophosphate (DFP). Is not inhibited by BPTI, antithrombin and EDTA. Monomer. Expressed by the venom gland. N-glycosylated. Contains 4.4% of hexoses, 4.4% of hexosamines and 3.1% of sialic acids. Does not hydrolyze casein or asocasein, prothrombin, fibrinogen and fibrin. Does not induce or inhibit platelet aggregation (PubMed:9920400). Belongs to the peptidase S1 family. Snake venom subfamily.