Dipeptidyl peptidases (DPPs) mediate regulatory activity of their substrates and have been linked to a variety of diseases including type 2 diabetes, obesity and cancer. DPPs have post-proline dipeptidyl aminopeptidase activity, cleaving Xaa-Pro dipeptides from the N-termini of proteins. DPPs can bind specific voltage-gated potassium channels and alter their expression and biophysical properties and may also influence T cells. DPP proteins include DPRP1, DPRP2, DPP3, DPP7, DPP10, DPPX and CD26. DPRP1 (dipeptidyl-peptidase IV-related protein 1), also known as DPP8 (dipeptidyl-peptidase 8), DP8 or MSTP141, is a member of the peptidase S9B family of proteins that exhibit prolyl oligopeptidase activity. DPRP1 localizes to the cytoplasm and is ubiquitously expressed with predominant expression in placenta, brain, prostate, testis and muscle. DPRP1 is similar to CD26 (dipeptidyl peptidase IV) suggesting that it may be involved in immune function and participate in the activation of T-cells.