Xaa-Pro aminopeptidase 3, also known as aminopeptidase P3, is an enzyme that in humans is encoded by the XPNPEP3 gene.[1][2] XPNPEP3 localizes to mitochondria in renal cells and to kidney tubules in a cell type-specific pattern. Mutations in XPNPEP3 gene have been identified as a cause of a nephronophthisis-like disease.[2]