Chemical Composition of Gastrin and Other Gastrointestinal Hormones

Chemical Composition of Gastrin and Other Gastrointestinal Hormones

Gastrin, cholecystokinin, and secretin are all largepolypeptides with approximate molecular weights, respectively, of 2000, 4200, and 3400. The terminal five amino acids in the gastrin and cholecystokinin molec-ular chains are the same. The functional activity of gastrin resides in the terminal four amino acids, and the activity for cholecystokinin resides in the terminal eight amino acids. All the amino acids in the secretin molecule are essential.

A synthetic gastrin, composed of the terminal four amino acids of natural gastrin plus the amino acid alanine, has all the same physiologic properties as the natural gastrin. This synthetic product is called pentagastrin.