Propeptide-mediated specific inhibition of a recombinant serine protease from indian malaria vector, Anopheles culicifacies

Serine proteases are a class of proteolytic enzymes that are synthesized as enzymically inactive zymogens and when required in the cell, they are activated by the removal of proregion. The role of proregions as potent and specific inhibitors of their associated protease has been established. Here, we investigated the inhibition of a recombinantly expressed and refolded Anopheles culicifacies serine protease (ACSP) that was isolated from the body tissue of an Indian malaria vector, A. culicifacies by its own N-terminally located 19 amino acid residue propeptide. The synthetic peptide identical to the propeptide, its three deletion mutants and leupeptin (a general serine protease inhibitor) were tested in vitro for their inhibitory activity towards recombinant ACSP. Amongst the five peptides tested, leupeptin displayed maximum inhibition closely followed by native propeptide. The reduction or loss of inhibitory potential of deletion mutants of propeptide revealed the importance of charged residues present in the propeptide for inhibition of the cognate enzyme.