This peptide hormone induces gall bladder contraction and the release of pancreatic enzymes in the gut. Its function in the brain is not clear. Expressed in brain, duodenum and small intestine. The precursor is cleaved by proteases to produce a number of active cholecystokinins. Turtle brain contains CCK-octapeptide (CCK8) and CCK7, whereas the gut contains intact CCK33, CCK40 and CCK58. Belongs to the gastrin/cholecystokinin family.