Pancreatic peptide tyrosine tyrosine (peptide YY or PYY) is a 36 amino acid peptide released in the ileum and colon in response to feeding. It acts through neuropeptide Y (NPY) receptors to reduce appetite, inhibit gastric motility, and increase water and electrolyte absorption in the colon. It is a selective agonist for NPY Y2 over Y1 (0.11nM and 1050nM, respectively).