Regulatory subunit of the blood coagulation factor X-activating enzyme. Activates coagulation factor X (F10) in a calcium-dependent manner by cleaving the Arg-Ile bond at position 234. Weakly hydrolyzes insulin B chain, fibrinogen and some components of the extracellular matrix in vitro, but does not activate prothrombin or plasminogen. Heterotrimer; disulfide-linked. The heterotrimer consists of 1 heavy chain (a metalloproteinase) and 2 light chains: LC1 and LC2. Expressed by the venom gland. N-glycosylated. Calcium is required for ligand binding. Belongs to the snaclec family.