This enzyme is closely associated with an endotoxin-sensitive hemolymph coagulation system in limulus (PubMed:2266134). Its active form catalyzes the conversion of coagulogen to insoluble coagulin gel (PubMed:977558, PubMed:7822328). Selective cleavage of 18-Arg-|- and 47-Arg-|- bonds in coagulogen to form coagulin and fragments. Inhibited by intracellular coagulation inhibitor 2/LICI-2 and to a lesser extent by intracellular coagulation inhibitor 3/LICI-3. In the active form, heterodimer of a light chain and a heavy chain; disulfide-linked (PubMed:2266134, PubMed:7822280). Forms a covalent heterodimer with intracellular coagulation inhibitor 2/LICI-2 (PubMed:7822280). Secreted in hemolymph probably upon bacterial lipopolysaccharide (LPS) stimulation. Expressed in hemocytes (at protein level). The clip domain consists of 35-55 residues which are 'knitted' together usually by 3 conserved disulfide bonds forming a clip-like compact structure. Proteolytically cleaved into its mature active form by serine protease factor B (PubMed:2266134, PubMed:4030738). Cleavage produces a 25 kDa light chain containing the CLIP domain and a catalytic 31 kDa heavy chain which remain covalently associated through an interchain disulfide bond (PubMed:2266134, PubMed:4030738). Proteolytically cleaved by clotting factor G subunit beta (PubMed:7822328). Contains six O-linked carbohydrate chains in the N-terminal light chain. Belongs to the peptidase S1 family. CLIP subfamily.