Exendin-4 is a novel 39-amino acid peptide isolated from the venom of the Gila monster Heloderma suspectum. It shares 53% sequence homology with GLP-17-36amide and interacts with the same membrane receptor. Exendin-4 enhances glucose-dependent insulin secretion, suppresses inappropriately elevated glucagon secretion, and slows gastric emptying in vivo. It also promotes β-cell proliferation and neogenesis in vitro and in animal models. Recombinant Exendin-4 is E. coli expression of a synthetic DNA squence encoding the 39 amino acid of Exendin-4.