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. [provided by RefSeq].