NPY4R (Y4) has been reported to be expressed at highest levels in brain, coronary artery and ileum, low levels in pancreas and kidney. It is also been detected in colon and small intestine and isolated from human colon and head/neck libraries. It is one of the receptors for neuropeptide Y and peptide YY. The rank order of affinity of this receptor for pancreatic polypeptides is PP, PP (2-36) and [Ile-31, Gln-34] PP >[Pro-34] PYY >PYY and [Leu-31, Pro-34] NPY >NPY >PYY (3-36) and NPY (2-36) >PP (13-36) >PP (31-36) >NPY free acid. Ligand: Neuropeptide Y, Peptide YY.