PEPD also known as Xaa-Pro dipeptidase isoform1. The protein forms a homodimer that hydrolyzes dipeptides or tripeptides with C-terminal proline or hydroxyproline residues. The enzyme serves an important role in the recycling of proline, and may be rate limiting for the production of collagen. Mutations in this gene result in prolidase deficiency, which is characterized by the excretion of large amount of di- and tri-peptides containing proline. Recombinant human PEPD, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.