The gastrointestinal tract is the largest immune organ in the human body. The gastrointestinal tract refers to the digestive tract from the gastric pylorus to the anus, including the stomach, small intestine, large intestine, and other parts. The gut is the longest part of the digestive tract and the most important part of its function. The gastrointestinal tract is not a simple pipeline composed of muscles and mucous membranes, but a whole that functions under the innervation of a complex nervous system. The gastrointestinal tract is the main organ of the digestive system, which absorbs enough water and essential nutrients for the body. The variety and range of gastrointestinal diseases are wide. Gastrointestinal diseases mainly refer to general inflammatory gastrointestinal diseases (acute and chronic gastritis, Crohn’s disease, ulcerative colitis, acute and chronic appendicitis, etc.), peptic ulcer, stomach cancer, esophageal cancer, colorectal cancer, irritable bowel syndrome, bacillary dysentery, intestinal obstruction, short bowel syndrome, large intestine polyps, anal fissure, anal fistula, etc.
Summary of peptides for gastrointestinal studies
1. Motilin
Motilin is a 22-amino-acid hormone, released by the enteroendocrine M cells of the duodenum and proximal jejunum.
| Name | CAS | Sequence |
| Motilin, canine | 85490-53-5 | FVPIFTHSELQKIREKERNKGQ |
| Motilin (26-47), human, porcine | 52906-92-0 | FVPIFTYGELQRMQEKERNKGQ |
2. Gastrin
Gastrin is produced by G cells located in the gastric antrum and is the primary endocrine regulator of the secretory phase of a protein meal. The main function of gastrin is to stimulate gastric acid secretion, promote gastrointestinal motility, and participate in the maintenance of iron homeostasis. At the same time, gastrin can also stimulate the secretion of the pancreas, bile, and intestinal juice, and further decompose the food in the small intestine, which is beneficial to the absorption of nutrients in the small intestine.
| Name | CAS | Sequence |
| Gastrin I (human) | 10047-33-3 | Pyr–GPWLEEEEEAYGWMDF-NH2 |
| [Leu15]-Gastrin I (human) | 39024-57-2 | Pyr-GPWLEEEEEAYGWLDF |
| Gastrin I (1-14), human | 100940-57-6 | Glp-GPWLEEEEEAYGW |
| CCK-4 Acetate | 35144-91-3 | Trp-Met-Asp-Phe-NH2 |
| Pentagastrin | 5534-95-2 | Boc-β-Ala-Trp-Met-Asp-Phe-NH2 |
| Mini Gastrin I, human | 54405-27-5 | LEEEEEAYGWMDF-NH2 |
| Big Gastrin-1, human | 60675-77-6 | Pyr-LGPQGPPXLVADPSKKQGPWLEEEEEEAYGWMDF-NH2 |
| Gastrin I rat | 81123-06-0 | XRPPMEEEEEAYGWMDF |
3. Bombesin
Bombesin (BBS) is a 14-amino-acid peptide first isolated from the skin of the frog, Bombina bombina, in 1970 by Erspamer. It stimulates the release of gastrin and pancreatic enzymes and causes contraction of the gallbladder.
| Name | CAS | Sequence |
| Bombesin | 31362-50-2 | Glp-QRLGNQWAVGHLM-NH2 |
| Bombesin nonapeptide | 55750-00-0 | NQWAVGHLM |
4. Tachykinin
The tachykinins are a family of small peptides sharing a common C-terminal sequence, Phe-Xaa-Gly-Leu-Met-NH2, whose main members are SP, neurokinin A, and neurokinin B.
| Name | CAS | Sequence |
| Eledoisin | 69-25-0 | XPSKDAFIGLM |
| Kassinin | 63968-82-1 | DVPKSDQFVGLM |
| Neurokinin A | 86933-74-6 | HKTDSFVGLM |
| Neurokinin A(4-10) | 97559-35-8 | DSFVGLM-NH2 |
| Neurokinin B | 86933-75-7 | DMHDFFVGLM-NH2 |
| Substance P (1-7) | 68060-49-1 | RPKPQQF |
5. Somatostatin
Somatostatin belongs to the expanding family of small regulatory peptides which exert a variety of actions in different organ systems throughout the body.
| Name | CAS | Sequence |
| Octreotide | 83150-76-9 | FCFWKTCT (Disulfide bridge: Cys2-Cys7) |
| Octreotide Acetate | 79517-01-4 | FCFWKTCT |
6. Vasoactive intestinal peptide (VIP) and related peptides
The vasoactive intestinal polypeptide (VIP) is a member of a family of homologous neuro- and endocrine peptides which has three separate groups distinguished by the receptors which recognize them.
| Name | CAS | Sequence |
| Prepro VIP (111-122), human | 123025-94-5 | VSSNISEDPVPV |
| Prepro VIP (81-122), human | 111366-38-2 | HADGVFTSDFSKLLGQLSAKKYLESLMGKRVSSNISEDPVPV |
| VIP(6-28)(human, rat, porcine, bovine) | 69698-54-0 | FTDNYTRLRKQMAVKKYLNSILN-NH2 |
| [D-p-Cl-Phe6,Leu17]-VIP | 102805-45-8 | HSDAVXXDNYXRLRKQLAVKKYLNSXLN |
7. Neurotensin
Neurotensin is a 13–amino acid peptide originally detected in the bovine hypothalamus. Neurotensin can protect the airway from gastric mucosal injury caused by cold stimulation and can inhibit gastric acid secretion.
| Name | CAS | Sequence |
| Neurotensin(8-13) | 60482-95-3 | RRPYIL |
| Neurotensin | 39379-15-2 | Pyr-LYENKPRRPYIL |
| [Gln4]-Neurotensin | 61445-54-3 | Pyr-LYQNKPRRPYIL |
| Kinetensin | 103131-69-7 | IARRHPYFL |
| Xenopsin | 51827-01-1 | Glp-GKRPWIL |
8. Cholecystokinin
Cholecystokinin is secreted by cells of the upper small intestine. Its secretion is stimulated by the introduction of hydrochloric acid, amino acids, or fatty acids into the stomach or duodenum.
| Name | CAS | Sequence |
| Cholecystokinin Octapeptide (desulfated) | 25679-24-7 | DYMGWMDP |
| CCK-4 Acetate | 35144-91-3 | Trp-Met-Asp-Phe-NH2 |
9. Secretin
Secretin is a gastrointestinal peptide and a member of the pituitary adenylate cyclase-activating polypeptide (PACAP)/glucagon superfamily Sherwood et al.
| Name | CAS | Sequence |
| Secretin (28-54), human | 108153-74-8 | HSDGTFTSELSRLREGARLQRLLQGLV-NH2 |
| Secretin Acetate | 10813-74-8 | HSDGTFTSELSRLRDSARLQRLLQGLV-NH2 |
| Secretin (33-59), rat | 121028-49-7 | HSDGTFTSELSRLQDSARLQRLLQGLV-NH2 |
| Secretin, canine | 110786-77-1 | HSDGTFTSELSRLRESARLQRLLQGLV-NH2 |
| Secretin (5-27), porcine | 19665-15-7 | TFTSELSRLRDSARLQRLLQGLV-NH2 |
10. Pancreatic polypeptide
Pancreatic polypeptide (PP) is a 36–amino acid, 4.2-kDa polypeptide secreted by the islet F cells. PP belongs to the peptide YY/neuropeptide Y family of polypeptides.
| Name | CAS | Sequence |
| Pancreatic Polypeptide, bovine | 179986-89-1 | APLEPEYPGDNATPEQMAQYAAELRRYINMLTRPRY-NH2 |
| Pancreatic Polypeptide, human | 75976-10-2 | APLEPVYPGDNATPEQMAQYAADLRRYINMLTRPRY-NH2 |
| Pancreatic Polypeptide, rat | 90419-12-8 | APLEPMYPGDYATHEQRAQYETQLRRYINTLTRPRY-NH2 |
11. Peptide YY
Peptide YY (PYY) is a 36-amino-acid gut hormone released by L cells of the ileum/colon in proportion to ingested calories. PYY is functionally related to NPY and binds to the Y family of receptors, Y1R–Y6R.
| Name | CAS | Sequence |
| Peptide YY (3-36) | 126339-09-1 | IKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-NH2 |
| Peptide YY (3-36) Human | 123583-37-9 | IKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY |
| Peptide YY (human) | 118997-30-1 | YPIKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-NH2 |
12. Neuropeptide Y
Neuropeptide Y (NPY) is a vasoconstricting peptide that is released together with NE from sympathetic nerve endings.
| Name | CAS | Sequence |
| Neuropeptide Y (human, rat) | 90880-35-6 | YPSKPDNPGEDAPAEDMARYYSALRHYINLITRQRY-NH2 |
| Neuropeptide Y (13-36), amide, human | 122341-40-6 | PAEDMARYYSALRHYINLITRQRY-NH2 |
| Neuropeptide Y (22-36) | 119019-65-7 | SALRHYINLITRQRY-NH2 |
| Neuropeptide Y(29-64) | 303052-45-1 | YPSKPDNPGEDAPAEDMARYYSALRHYINLITRQRY |
| Neuropeptide Y, free acid, human, rat | 99575-89-0 | YPSKPDNPGEDAPAEDMARYYSALRHYINLITRQRY |
13. Opioid peptide
Opioid peptides are the endogenous ligands at opioid receptors.
| Name | CAS | Sequence |
| [D-Ala2]-Leu-Enkephalin-Arg | 81733-79-1 | Tyr-D-Ala-Gly-Phe-Leu-Arg |
| Dynorphin A(1-13) | 72957-38-1 | YGGFLRRIRPKLK |
| Dynorphin B (1-13) | 83335-41-5 | YGGFLRRQFKVVT |
| Met-Enkephalin | 58569-55-4 | YGGFM |
| N-Acetyl-α-Endorphin | 88264-63-5 | Ac-YGGFMTSEKSQTPLVT |
| β-Endorphin rat | 77367-63-6 | YGGFMTSEKSQTPLVTLFKNAIIKNVHKKGQ |
| β-Casomorphin, human | 102029-74-3 | YPFVEPI |
| β-Casomorphin (1-3), amide | 80705-23-3 | YPF-NH2 |
| β-Casomorphin (1-5), amide, bovine | 83936-23-6 | Y-d-Ala-FPM-NH2 |
| β-Casomorphin (1-6), bovine | 77434-43-6 | YPFPGP |
| β-Casomorphin (1-7), bovine | 72122-62-4 | YPFPGPI |
| α-Neoendorphin 1-8 | 83339-89-3 | YGGFLRKY |
| β-Neoendorphin | 77739-21-0 | YGGFLRKYP |
14. Gastric Inhibitory Polypeptide
GIP is a 42-amino-acid peptide hormone encoded by a single gene. GIP mRNA is expressed only in the gut, specifically in the K cells, the majority of which are located in the proximal duodenum.
| Name | CAS | Sequence |
| GIP (human) | 100040-31-1 | YAEGTFISDYSIAMDKIHQQDFVNWLLAQKGKKNDWKHNITQ |
| GIP (1-39) | 725474-97-5 | YAEGXFXSDYSXAMDKXRQQDFVNWLLAQKGKKSDWKHN |