This peptide hormone induces gall bladder contraction and the release of pancreatic enzymes in the gut. Its function in the brain is not clear. Binding to CCK-A receptors stimulates amylase release from the pancreas, binding to CCK-B receptors stimulates gastric acid secretion. Binds to CCK-A receptors in the pancreas and CCK-B receptors in the brain. The shortest form (CCK8) is predominantly found in the brain, whereas the larger ones are found in the intestine. The precursor is cleaved by proteases to produce a number of active cholecystokinins. Sulfation of Tyr-97 is essential for receptor activation. Belongs to the gastrin/cholecystokinin family.