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 KPI104 and KPI106 (PubMed:23662629). Composed of a mini chain and a large chain. The large chain may be split into heavy and light chain. All chains are held together by disulfide bonds. Belongs to the peptidase C1 family.