Serine protease inhibitor that inhibits proclotting enzyme and to a lesser extent clotting factor C and clotting factor G. Monomer (PubMed:7822280). Forms a covalent heterodimer with clotting factor C chain B (PubMed:7822280). Forms a covalent heterodimer with proclotting enzyme heavy chain (PubMed:7822280). Localizes in the large granules of hemocytes (PubMed:7822280). Secreted in hemolymph in response to external stimuli (PubMed:7822280). Specifically expressed in hemocytes (at protein level). Belongs to the serpin family.