The function of XPNPEP1 (X-prolyl aminopeptidase 1, ENSG00000108039) is as follows. Metalloaminopeptidase that catalyzes the removal of a penultimate prolyl residue from the N-termini of peptides, such as Arg- Pro-Pro (PubMed:11106490, PubMed:18515364, PubMed:35165443). Contributes to the degradation of bradykinin (PubMed:11106490). {ECO:0000269|PubMed:11106490, ECO:0000269|PubMed:18515364, ECO:0000269|PubMed:35165443}.