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Gut & brain peptide

Cholecystokinin

Cholecystokinin (CCK) is a peptide hormone and neurotransmitter released from intestinal I-cells and also produced widely in the brain. It triggers gallbladder contraction and pancreatic enzyme secretion after fatty meals and signals satiety, making it a foundational gut–brain peptide.

By The Peptides Codex Editorial TeamReviewed July 10, 2026
Length
n/a
Class
Gut & brain peptide
Function
Stimulates gallbladder contraction, pancreatic enzyme release, and satiety
Context
Endogenous peptide; the CCK-8 fragment is used in research and imaging contexts

A classic gut–brain peptide — and one of the most abundant neuropeptides in the CNS.

Also known as: CCK · CCK-8 · pancreozymin

Part of the Metabolic & GLP-1 peptides cluster

Overview

Cholecystokinin (CCK) is a peptide hormone and neurotransmitter released from intestinal I-cells and also produced widely in the brain. It triggers gallbladder contraction and pancreatic enzyme secretion after fatty meals and signals satiety, making it a foundational gut–brain peptide.

Source & context

Biological / chemical source: Intestinal I-cells and central nervous system neurons

Primary research or clinical context: Endogenous peptide; the CCK-8 fragment is used in research and imaging contexts

A family of active fragments

CCK is processed from a single precursor into several C-terminally amidated forms of different lengths — CCK-58, CCK-33, CCK-22 and the widely studied CCK-8. A sulfated tyrosine near the C-terminus is critical for full activity at the CCK-A receptor, a nice example of how post-translational modification tunes potency.

Gut and brain roles

In the gut, CCK coordinates digestion of fat and protein by stimulating bile release and pancreatic enzymes. In the brain it is one of the most abundant neuropeptides and is studied in satiety, anxiety and reward pathways. This page describes that physiology for educational purposes only.

FAQ about Cholecystokinin

What is Cholecystokinin?+

Cholecystokinin (CCK) is a peptide hormone and neurotransmitter released from intestinal I-cells and also produced widely in the brain. It triggers gallbladder contraction and pancreatic enzyme secretion after fatty meals and signals satiety, making it a foundational gut–brain peptide.

Is Cholecystokinin an approved medicine?+

Cholecystokinin is discussed here as a research / educational topic. Endogenous peptide; the CCK-8 fragment is used in research and imaging contexts. This is not medical advice.

What is the typical length of Cholecystokinin?+

Cholecystokinin is not a classic amino-acid chain peptide in the same sense; see the profile for classification details.

Related peptides

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Follistatin-315
Activin-binding glycoprotein isoform
Follistatin-315 (FS-315) is the longer of two follistatin isoforms generated by alternative splicing of the FST gene. Follistatin binds activin and related TGF-beta ligands, including myostatin. FS-315 is an investigational research protein, not authorized by Health Canada; this page is educational only.
Oxyntomodulin
Gut hormone
Oxyntomodulin is a 37-amino-acid gut hormone released from intestinal L-cells after eating. Because it activates both the GLP-1 and glucagon receptors on its own, it is frequently cited as the natural inspiration for engineered dual-agonist metabolic peptides.
Orexin-A
Neuropeptide
Orexin-A (hypocretin-1) is a 33-amino-acid hypothalamic neuropeptide central to the regulation of wakefulness and arousal. Loss of orexin signaling is a well-studied feature of narcolepsy research.

References & further reading

  1. 1.Wikipedia — Cholecystokinin
  2. 2.UniProt — CCK, Cholecystokinin, human (P06307)
Disclaimer: Educational content only. Not medical advice. Not instructions for human use. Research peptides and unapproved products may be restricted or illegal to market for human consumption in your jurisdiction. Consult qualified professionals and applicable law.
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Cite this: Peptides Codex — Cholecystokinin educational profile.
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