The activation peptides of aspartic proteinases plays role as inhibitors of the active site.These peptide segments, or pro-parts, are deemed important for correct folding, targeting, and control of the activation of aspartic proteinase zymogens.The pronapsin A gene is expressed predominantly in lung and kidney.Its translation product is predicted to be a fully functional, glycosylated aspartic proteinase precursor containing an RGD motif and an additional 18 residues at its C-terminus.