XPNPEP1 also known as Xaa-Pro aminopeptidase 1 isoform 1, is encodes the cytosolic form of a metalloaminopeptidase that catalyzes the cleavage of the N-terminal amino acid adjacent to a proline residue. This product may play a role in degradation and maturation of tachykinins, neuropeptides, and peptide hormones. Recombinant human XPNPEP1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.