This truncated Exendin-4 peptide, Exendin (9-39) amide, is a potent Glucagon-Like Peptide 1 (GLP-1) receptor antagonist. Unlike the full length Exendin-4 (a GLP-1 agonist), Exendin (9-39) antagonizes GLP-1–stimulated insulin release after food intake. It is a competitive inhibitor of Exendin-3 and Exendin-4.
H - Asp - Leu - Ser - Lys - Gln - Met - Glu - Glu - Glu - Ala - Val - Arg - Leu - Phe - Ile - Glu - Trp - Leu - Lys - Asn - Gly - Gly - Pro - Ser - Ser - Gly - Ala - Pro - Pro - Pro - Ser - NH2