May play a role in proteolysis leading to mobilization of nitrogen during senescence and starvation. Hydrolysis of proteins, acting as an aminopeptidase (notably, cleaving Arg-|-Xaa bonds) as well as an endopeptidase. Interacts with VSR1/BP80B. Predominantly vacuolar. From the Golgi apparatus, transported to the lytic vacuole (LV) in clathrin-coated vesicles (CCVs) via the prevacuolar compartment (PVC). In root elongating cells and stomata, localized in central vacuole and in small compartments (LVs, PVCs, Golgi bodies or small vacuoles). Limited to central vacuole in root elongated cells, leaf epidermal cells and trichomes of the lower face of the leaf blade. Limited to small compartments in root cap and apex cells, hypocotyl parenchyma cells and trichomes of the upper face of the leaf blade. A number of isoforms are produced. According to EST sequences. Expressed in leaves (at protein level). Induced during senescence. Strongly induced by ethylene and slightly by abscisic acid. Repressed by cytokinin and darkness. Seems to be not affected by dehydration. Belongs to the peptidase C1 family.