Probable inactive serine protease which plays an essential role in the innate immune response against bacteria and protozoa infection by activating the melanization cascade (PubMed:24039584, PubMed:33045027). Binds to the surface of parasite P.berghei ookinetes and bacterium E.coli where it promotes the accumulation of mature TEP1 which leads to the melanization of the microbe (PubMed:24039584, PubMed:33045027). Interacts with mature TEP1 and to a lesser extent with full-length TEP1; the interaction is induced by microbial infection. Secreted into the hemolymph. The clip domain consists of 35-55 residues which are 'knitted' together usually by 3 conserved disulfide bonds forming a clip-like compact structure. RNAi-mediated knockdown increases the number of P.berghei oocysts in the mosquito midgut (PubMed:24039584). In the hemolymph, prevents the cleavage of TEP1 into its mature form thereby preventing TEP1 binding to the surface of bacterium E.coli or parasite P.berghei ookinetes (PubMed:24039584). In response to E.coli infection, cleavage of CLIPA8, CLIPA28 and CLIPC9 in the hemolymph is impaired and phenoloxidase (PO) activity is severely decreased (PubMed:24039584, PubMed:33045027). Also reduces E.coli melanization (PubMed:33045027). Belongs to the peptidase S1 family. CLIP subfamily. Although it belongs to peptidase S1 family, the residues corresponding to the serine protease catalytic triad (Asp-His-Ser) are not conserved suggesting that SPCLIP1 lacks catalytic activity.