Dipeptidyl Peptidase 4
Nature has evolved a number of regulatory, neuronal, and immune peptides with a proline residue at the penultimate position determining their structural conformation and biological activity. Generally, the proline peptide bonds are resistant to proteolytic cleavage, yet an exclusive number of postproline-specific peptidases have emerged to regulate these peptides. The best-characterized one is dipeptidyl peptidase 4 (DPP4), though additional functional homologues of DPP4-like enzymes have been discovered, some structurally related, others without any structural homology. Since DPP4 is involved in glucose homeostasis and immune response, it is of medical and pharmaceutical interest to distinguish between these enzymes (Klemann et al. 2016; Lambeir et al. 2003; Wagner et al. 2016b).