Angler fish peptide YG (APY) which is 64% homologous to both neuropeptide Y (NPY) and peptide YY (PYY) will be synthesized by solid phase method. The peptide will be tested for PYY and NPY-like activities, namely the effects on pancreatic secretion and on intestinal blood flow in dogs. Amidated form of APY will be synthesized to investigate whether the APY amide will have the same biological activity as the glycine extended form, the intact hormone. Minimum sequence requirements for activity will be examined by the synthesis and investigation of the biological properties of selected fragments of APY. Antibodies raised against the intact hormone will be used to determine whether APY-like immunoreactive peptide is present in mammals. Selected fragments and analogs of PYY and NPY will be synthesized to determine the sites involved in receptor binding and biological activity. Results of these experiments will form the basis for the development of agonistic and antagonistic peptides for PYY and NPY.