A polypeptide released postprandially in proportion to meal energy content by endocrine L cells in the ileum and colon in order to regulate appetite; cleaved to PYY (3-36}), a preferred agonist at presynaptic inhibitory type 2 NPY autoreceptors (EC50 = 11.4 nM in human colon mucosa); associated with dose-dependent weight loss in various obesity models