Endopeptidase with selective post-Arg cleavage site (PubMed:16399077, PubMed:7737188). Functions in the innate immune response to fungal and Gram-positive bacterial infections (PubMed:16399077, PubMed:26707571, PubMed:34022191). Upon pathogen infection promotes nodulation; a cellular defense response in which hemocytes surround and isolate invading pathogens forming aggregates called nodules (PubMed:26707571, PubMed:34022191). Involved in activating nodule formation in response to infection with M.luteus, E. coli or S.cerevisiae (PubMed:34022191). Able to bind the microbes M.luteus, E. coli or S.cerevisiae (PubMed:34022191). According to another report, does not bind microorganisms (PubMed:26707571). Inhibited by (p-amidinophenyl) methanesulfonyl fluoride, p-nitrophenyl-p'-guanidinobenzoate, D-phenylalanyl-L-prolyl-L-arginyl chloromethane, leupeptin, antipain and to a lesser extent by antithrombin III. In the active form, heterodimer of a light chain and a heavy chain; disulfide-linked. In larvae, secreted in the hemolymph (PubMed:16399077, PubMed:7737188, PubMed:26707571). Only the uncleaved form is detected in hemolymph (PubMed:26707571). Uncleaved (42 kDa) and cleaved (29 kDa) forms, are weakly expressed in hemocytes (PubMed:26707571). Detected in the cytoplasm of various hemocytes including plasmatocytes, oenocytoids, granulocytes and prohemocytes (PubMed:26707571). Cleaved and uncleaved forms also localize to immune defense nodules that have been induced by injection with E.coli, M.luteus or S.cerevisiae cells (PubMed:26707571). In larvae, expressed in the fat body and hemocytes. Up-regulated in plasma in response to infection with S.cerevisiae and M.luteus. 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 for activation (PubMed:16399077). Cleavage produces a light chain and a catalytic heavy chain which remains covalently associated probably through an interchain disulfide bond (Probable). Belongs to the peptidase S1 family. CLIP subfamily. The light chain lacks the CLIP domain which is different from other CLIP protease family members. This is due to a cleavage at position 83 which is seen in vitro but whose physiological relevance is unclear.