Catalytic subunit of blood coagulation factor X-activating enzyme. Activates coagulation factor X (F10) by cleaving the Arg(234)-Ile(235) bond, activates coagulation factor IX (F9) by cleaving the Arg(226)-Val(227) bond and is also able to activate protein C (PROC). Specifically activates several components of the blood clotting system, including coagulation factor X, coagulation factor IX and protein C by cleavage of Arg-|-Xaa bonds. Has no action on insulin B chain. Binds 1 zinc ion per subunit. Calcium is required for the activity of the heterotrimer. Optimum pH is 7.5-8.0. Heterotrimer; disulfide-linked. The heterotrimer consists of 1 heavy chain and 2 light chains (lectins): LC1 and LC2 (AC Q7T045 and AC Q696W1). Expressed by the venom gland. N-glycosylated. Contains 8.0% of hexoses, 2.5% of hexosamines and 2.5% of sialic acids. Belongs to the venom metalloproteinase (M12B) family. P-III subfamily. P-IIId sub-subfamily.