CCK39

CCK-39 is a peptide hormone belonging to the cholecystokinin (CCK) family. It is one of several endogenous forms generated from the larger precursor protein pro-cholecystokinin (pro-CCK) through tissue-specific proteolytic processing. CCK-39 is produced in both the gastrointestinal tract and the brain, with its exact abundance varying by species and physiological state. Like other CCK peptides, it features a conserved C-terminal region that ends with an amidated phenylalanine, a structural feature important for receptor interaction, and its activity is modulated by tyrosine sulfation.

Biochemistry and receptors: The CCK-39 peptide shares the characteristic motifs common to CCK fragments and acts primarily through CCK receptors. The sulfo-tyrosine residue and the C-terminal amide enhance binding to the CCK1 receptor (also known as CCK-A) and interact with the CCK2 receptor (CCK-B) to mediate physiological responses. The exact receptor affinity can vary among CCK peptide forms, but CCK-39 participates in the same general signaling pathways as other mature CCK peptides.

Biosynthesis and distribution: Pro-CCK is expressed in enteroendocrine I cells of the small intestine and in certain neurons. Enzymatic processing yields multiple CCK forms, including CCK-39, which is released in response to meals containing fats and proteins. Circulating CCK-39 can exert effects both peripherally and centrally, depending on its site of release and transport.

Physiological roles: In the gut, CCK-39 stimulates pancreatic enzyme secretion, promotes gallbladder contraction, relaxes the sphincter of Oddi, and slows gastric emptying to aid digestion. It contributes to meal-induced satiety and can influence digestive motility. In the brain, CCK peptides are implicated in modulating anxiety, pain perception, and memory processes.

Research and context: CCK-39 is primarily studied in research settings using immunoassays or mass spectrometry to understand digestive physiology, satiety signaling, and CNS effects of CCK peptides. Its specific contributions relative to other CCK forms continue to be explored.