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pepsin, enzyme produced in the mucosal lining of the stomach that acts to degrade protein. Pepsin is one of three principal protein-degrading, or proteolytic, enzymes in the digestive system, the other two being chymotrypsin and trypsin. The three enzymes were among the first to be isolated in crystalline form. During the process of digestion, these enzymes, each of which is particularly effective in severing links between particular types of amino acids, collaborate to break down dietary proteins to their components, i.e., peptides and amino acids, which can be readily absorbed by the intestinal lining. In the laboratory studies pepsin is most efficient in cleaving bonds involving the aromatic amino acids, phenylalanine, tryptophan, and tyrosine. Pepsin is synthesized in an inactive form by the stomach lining; hydrochloric acid, also produced by the gastric mucosa, is necessary to convert the inactive enzyme and to maintain the optimum acidity (pH 1–3) for pepsin function. Pepsin and other proteolytic enzymes are used in the laboratory analysis of various proteins; pepsin is also used in the preparation of cheese and other protein-containing foods.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a proteolytic enzyme of the hydrolase class, found in the gastric juice of mammals, birds, reptiles, and most species of fish. Pepsin breaks down proteins and peptides. It was first recognized in 1836 by T. Schwann and isolated in crystal form in 1930 by J. Northrop.

Pepsin is a globular protein with a molecular weight of approximately 34,500. A pepsin molecule is a polypeptide chain consisting of 340 amino-acid residues, three disulfide bonds (—S—S—), and phosphoric acid. The isoelectric point of pepsin is approximately equal to pH 1.0. Therefore, pepsin is stable in a strongly acid medium and reaches its maximum activity at pH 1–2, the pH of gastric juice. It undergoes denaturation at pH 6.0.

Pepsin is an endopeptidase, that is, an enzyme that splits the central peptide bonds in protein and peptide molecules, except keratins and other scleroproteins, to form simpler peptides and free amino acids. It very rapidly hydrolyzes peptide bonds formed by the aromatic amino acids tyrosine and phenylalanine; however, unlike the proteolytic enzymes trypsin and chymotrypsin, it does not exhibit a strong specificity.

Pepsin is produced by the gastric chief cells in the form of inactive pepsinogen. Pepsinogen is then converted to pepsin by the splitting off of several peptides, including a pepsin inhibitor, from the N-terminal section of pepsinogen. The activation process involves several stages and is catalyzed by the hydrochloric acid in gastric juice and by pepsin itself (autocatalysis).

Pepsin is used in the laboratory investigation of the primary structure of proteins, in cheese-making, and in the treatment of certain gastrointestinal diseases.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A proteolytic enzyme found in the gastric juice of mammals, birds, reptiles, and fishes.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


, pepsine
a proteolytic enzyme produced in the stomach in the inactive form pepsinogen, which, when activated by acid, splits proteins into peptones
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
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Although isoforms were detected early at 2 DPH, the zymogram and the colorimetric technique does not necessarily mean that it is pepsin. In our study, the homogenate of the whole body of the larva was performed, which could cause cathepsins to be detected, and although they are aspartic proteases dedicated to protein hydrolysis, they perform it intracellularly, so they do not belong to the group of digestive proteases (Moyano et al., 2013).
Hydrolysis with the pepsin showed enthalpies 816.20 and 144.40 J/g corresponding to 50.518 and 108.768 0C, respectively.
However, current data measuring the concentration of pepsin and pepsinogen in middle ear fluid report conflicting results, and the association between GER and OME remains inconclusive.
Residual activity of the recombinant endo-[beta]-1,4-glucanase, after treating with pepsin or trypsin after 1h, 3h, 5h, and 7h (Fig.5).
Enzyme Pepsin 1:2.500 (powder, [greater than or equal to] 400 units/mg protein, P7125, SIGMA[R]) and the other analytical grade reagents (PA) were acquired from Sigma-Aldrich Brasil Ltda company (Sao Paulo, SP, Brazil).
Acidic proteases have been categorized into three families, that is, pepsin (A1), retropepsin (A2), and enzymes from pararetroviruses (A3).
What's more, says Gabbard, "pepsin helps digest proteins.
Symptoms of acid peptic disease are primarily due to imbalance between protective and damaging factors of gastric mucosa, Helicobacter pylori, Smoking/Alcohol, Spicy food Duodenogastric bile reflux, Gastric stasis, abnormal acid secretion, pepsin secretion (e.g.
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Its flagship compound ITV-1 is a suspension of Inactivated Pepsin Fragment, which studies have shown is effective in the treatment of HIV.
A lower pH positively influenced the conversion of pepsinogen to pepsin as pepsin works better in 2 to 3 pH range (Zhao et al., 2011).