BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Human preprogastrin contains 101 amino acids (AA) including a signal peptide (21 AA), spacer sequence (37 AA), gastrin component (34 AA), and a 9 AA extension segment at the carboxyl terminus. The enzymatic processing of preprogastrin produces all of the known physiologically active forms of gastrin.

Detailed explanation-2: -Phenylalanine and tryptophan were significantly more potent stimulants of gastric acid secretion and of pancreatic polypeptide and gastrin release than any of the other amino acids tested.

Detailed explanation-3: -Cholecystokinin (CCK) and gastrin together constitute a family of homologous peptide hormones, which are both physiological ligands for the gastrin/CCK-B receptor, whereas the CCK-A receptor binds only sulfated CCK-peptides. CCK peptides are mainly produced in small intestinal endocrine I-cells and in cerebral neurons.

Detailed explanation-4: -Four gastrointestinal peptides are classified as hormones: gastrin, cholecystokinin (CCK), secretin, and glucose-dependent insulinotropic peptide (or gastric inhibitory peptide, GIP). Paracrines, like hormones, are peptides secreted by endocrine cells of the gastrointestinal tract.