Monitor peptide explained

Monitor peptide, also known as pancreatic secretory trypsin inhibitor I (PSTI-I) or pancreatic secretory trypsin inhibitor 61 (PSTI-61), is a peptide that plays an important role in the regulation of the digestive system, specifically the release of cholecystokinin (CCK).[1] [2] [3] [4]

Function

One of the primary functions of monitor peptide is to stimulate the release of CCK from the enteroendocrine cells of the small intestine.[4] CCK then acts on the gallbladder to release bile and on the pancreas to release digestive enzymes, which help to further break down the food. This coordinated response helps to ensure efficient digestion and absorption of nutrients.

Another function is to act as a competitive inhibitor of trypsin, which is a protease that can activate other proteases. It has been shown to prevent premature activation of pancreatic enzymes.

Its role as a feedback regulator has been well-described for decades.[5] Monitor peptide binds to intestinal epithelial cells and induces CCK-release, which enhances pancreatic secretion in the presence of nutritional protein in the duodenum. When all nutritional protein is digested, monitor peptide is bound by trypsin and subsequently degraded, resulting in decreasing CCK-release and a reduction of pancreatic secretion.

History

Monitor peptide was first discovered in 1984 by Fushiki et al.[4] [6] It was purified from rat bile-pancreatic juice and the peptide sequence was elucidated.[4]

Description

Monitor peptide is composed of 61 amino acids with a molecular weight of approximately 6500 daltons and is basic (PI = 9.0), acid stable, and heat resistant.[7] It is only found in the zymogen granules of pancreatic acinar cells.[7] Similar to CCK-releasing peptide (CCK-RP), it is trypsin sensitive and stimulates CCK release.[7] It is possible that it also stimulates the growth of intestinal epithelial cells.[8]

Notes and References

  1. Book: Shlomo Melmed, M.M. . Polonsky . K.S. . P. Reed Larsen . M.D.F. . Kronenberg . H.M. . Williams Textbook of Endocrinology . Elsevier Health Sciences . Internal Medicine . 2015 . 978-0-323-29738-7 . 2023-03-25 . 1714.
  2. Yamanishi . Rintaro . Kotera . Jun . Fushiki . Tohru . Soneda . Tomoko . Iwanaga . Toshihiko . Sugimoto . Etsuro . Characteristic and Localization of the Monitor Peptide Receptor . Bioscience, Biotechnology, and Biochemistry . Informa UK Limited . 57 . 7 . 1993 . 0916-8451 . 10.1271/bbb.57.1153 . 1153–1156.
  3. Graf . R. . Klauser . S. . Fukuoka . S.-I. . Schiesser . M. . Bimmler . D. . The Bifunctional Rat Pancreatic Secretory Trypsin Inhibitor/Monitor Peptide Provides Protection against Premature Activation of Pancreatic Juice . Pancreatology . Elsevier BV . 3 . 3 . 2003 . 1424-3903 . 10.1159/000070729 . 195–206.
  4. Miyasaka . Kyoko . Nakamura . Rieko . Funakoshi . Akihiro . Kitani . Kenichi . Stimulatory Effect of Monitor Peptide and Human Pancreatic Secretory Trypsin Inhibitor on Pancreatic Secretion and Cholecystokinin Release in Conscious Rats . Pancreas . Ovid Technologies (Wolters Kluwer Health) . 4 . 2 . 1989 . 0885-3177 . 10.1097/00006676-198904000-00001 . 139–144.
  5. Graf . Rolf . Bimmler . Daniel . 2006 . Biochemistry and Biology of SPINK-PSTI and Monitor Peptide . Endocrinology and Metabolism Clinics of North America . Elsevier BV . 35 . 2 . 333–343 . 10.1016/j.ecl.2006.02.005 . 0889-8529.
  6. Fushiki . Tohru . Fukuoka . Shin-ichi . Iwai . Kazuo . Stimulatory effect of an endogenous peptide in rat pancreatic juice on pancreatic enzyme secretion in the presence of atropine: Evidence for different mode of action of stimulation from exogenous trypsin inhibitors . Biochemical and Biophysical Research Communications . Elsevier BV . 118 . 2 . 1984 . 0006-291X . 10.1016/0006-291x(84)91335-4 . 532–537.
  7. Book: Thompson, J. . Gastrointestinal Endocrinology: Receptors and Post-Receptor Mechanisms . Elsevier Science . 2012 . 978-0-323-14642-5 . 2023-03-25 . 300.
  8. Fukuda . Masako . Fujiyama . Yoshihide . Sasaki . Masaya . Andoh . Akira . Bamba . Tadao . Fushiki . Tohru . 1998 . Monitor Peptide (Rat Pancreatic Secretory Trypsin Inhibitor) Directly Stimulates the Proliferation of the Nontransformed Intestinal Epithelial Cell Line, IEC-6 . Digestion . S. Karger AG . 59 . 4 . 326–330 . 10.1159/000007510 . 0012-2823.

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