Asparagine-specific endopeptidase that may be involved in processing of proteins targeted to vacuoles. Cysteine protease required for post-translational proteolysis of seed storage proteins in the protein storage vacuole (PSV) of developing seeds, by processing of proglutelin precursor to mature glutelin subunits, thus contributing to the formation of protein crystalline structures in PSV (Ref.1, PubMed:19154227, PubMed:19933265). Hydrolysis of proteins and small molecule substrates at -Asn-|-Xaa- bonds. Expressed in developing seeds. Auto-catalytic activation. In PAK22, higher quantities of 57 kDa polypeptides and lower levels of 40 kDa acidic and 20 kDa basic glutelin subunits in seeds due to reduced vacuolar processing enzyme (VPE) activity and leading to non-crystalline lattice structure of protein storage vacuoles (PSVs). Seedlings growth retardation. Belongs to the peptidase C13 family.