The Essential Amino Acid Domains in Salivary Peptide P-C That Potentiate Glucose-Induced Insulin Release and Inhibit Arginine-Induced Glucagon Release from Perfused Rat Pancreas

The amino acid domains in salivary peptide P-C (1-44 peptide fragments, P-C) that are essential to potentiate insulin release and inhibit glucagon release were investigated using isolated perfused rat pancreas. P-C significantly potentiated not only glucose (8.3 mM)-induced insulin release, but also arginine (10 mM)-induced insulin release. The essential domain responsible for potentiation of insulin release was the P-C-(23-29) fragment, 23KPQGPPP29, while that inhibiting glucagon release was the P-C-(12-18) fragment, 12HQQGPPP18. Since both domains share a common fragment, QGPP, these findings indicate that the functional amino acid sequences KP and HQ may potentiate insulin release and inhibit glucagon release, respectively.