XPNPEP3 Full-Length MS Protein Standard (NP_071381), Labeled with [U- 13C6, 15N4]-L-Arginine and [U- 13C6, 15N2]-L-Lysine, was produced in human 293 cells (HEK293) with fully chemically defined cell culture medium to obtain incorporation efficiency at Creative-Proteomics. The protein encoded by this gene belongs to the family of X-pro-aminopeptidases that utilize a metal cofactor, and remove the N-terminal amino acid from peptides with a proline residue in the penultimate position. This protein has been shown to localize to the mitochondria of renal cells, and have a role in ciliary function. Mutations in this gene are associated with nephronophthisis-like nephropathy-1. Alternatively spliced transcript variants encoding different isoforms have been noted for this gene, however, expression of some of these isoforms in vivo is not known.