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pepsin

 
Dictionary: pep·sin  pep·sine (pĕp'sĭn) pronunciation
also n.
  1. A digestive enzyme found in gastric juice that catalyzes the breakdown of protein to peptides.
  2. A substance containing pepsin, obtained from the stomachs of hogs and calves and used as a digestive aid.

[Greek pepsis, digestion (from peptein, to digest) + -IN.]


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A proteolytic enzyme found in the gastric juice of mammals, birds, reptiles, and fish. It is formed from a precursor, pepsinogen, which is found in the stomach mucosa. Pepsinogen is converted to pepsin either by hydrochloric acid, naturally present in the stomach, or by pepsin itself. See also Enzyme.

Pepsin is prepared commercially from the glandular layer of fresh hog stomachs. It is a part of the crude preparation known as rennet, which is used to curdle milk in preparation for cheese manufacture. Pepsin is also used for a variety of other applications in food manufacturing; to modify soy protein and gelatin, thereby providing whipping qualities; to modify vegetable proteins for use in nondairy snack items; to make precooked cereals into instant hot cereals; and to prepare animal and vegetable protein hydrolysates for use in flavoring foods and beverages.


Food and Nutrition: pepsin
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An enzyme in the gastric juice which hydrolyses proteins to give smaller polypeptides, known as peptones; an endopeptidase. Active only at acid pH, 1.5-2.5. Secreted as the inactive precursor pepsinogen, which is activated by acid.


Powerful enzyme in gastric juice (see stomach) that partially digests proteins in food. Glands in the stomach lining make pepsinogen, a zymogen (enzyme precursor) converted to pepsin by the hydrochloric acid in gastric juice. Pepsin is active only in the acid environment of the stomach (pH 1.5 – 2.5 or less); it is ineffective in the intestine (pH 7, neutral). It is used commercially in some cheese making, in the leather industry to remove hair and residual tissue from hides, and in the recovery of silver from discarded photographic films by digesting the gelatin layer that holds the silver.

For more information on pepsin, visit Britannica.com.

 
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.


A proteolytic enzyme that is the principal digestive component of gastric juice. It acts as a catalyst in the chemical breakdown of protein to form a mixture of polypeptides; it is formed from pepsinogen in the presence of acid or, autocatalytically, in the presence of pepsin itself. Pepsin also has milk-clotting action similar to that of rennin and thereby facilitates the digestion of milk protein.

  • p. barrier — the gastric mucosal mechanism which prevents rediffusion of hydrochloric acid back into gastric tissues; includes an electrical resistance, mucus, plus bicarbonate ions trapped in the mucus, endogenous prostaglandins.
Wikipedia: Pepsin
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pepsinogen 3, group I (pepsinogen A)
1PSO.png
Pepsin in complex with pepstatin.[1]
Identifiers
Symbol PGA3
Entrez 643834
HUGO 8885
OMIM 169710
RefSeq NM_001079807
UniProt P00790
Other data
EC number 3.4.23.1
Locus Chr. 11 q13
pepsinogen 4, group I (pepsinogen A)
Identifiers
Symbol PGA4
Entrez 643847
HUGO 8886
OMIM 169720
RefSeq NM_001079808
UniProt P00790
Other data
EC number 3.4.23.1
Locus Chr. 11 q13
pepsinogen 5, group I (pepsinogen A)
Identifiers
Symbol PGA5
Entrez 5222
HUGO 8887
OMIM 169730
RefSeq NM_014224
UniProt P00790
Other data
EC number 3.4.23.1
Locus Chr. 11 q13

Pepsin is an enzyme that is released by the chief cells in the stomach and that degrades food proteins into peptides. Pepsin was discovered in 1836 by Theodor Schwann[2] who also coined this enzyme's name from the Greek word pepsis, meaning digestion (peptein: to digest).[3] It was the first animal enzyme to be discovered, and, in 1929, it became one of the first enzymes to be crystallized, by John H. Northrop.[4] Pepsin is a digestive protease.[5]

Contents

Precursor

Pepsin is expressed as a pro-form zymogen, pepsinogen, whose primary structure has an additional 44 amino acids.

In the stomach, chief cells release pepsinogen. This zymogen is activated by hydrochloric acid (HCl), which is released from parietal cells in the stomach lining. The hormone gastrin and the vagus nerve trigger the release of both pepsinogen and HCl from the stomach lining when food is ingested. Hydrochloric acid creates an acidic environment, which allows pepsinogen to unfold and cleave itself in an autocatalytic fashion, thereby generating pepsin (the active form). Pepsin cleaves the 44 amino acids from pepsinogen to create more pepsin. Pepsin will digest up to 20% of ingested carbon bonds by cleaving preferentially after the N-terminal[6] of aromatic amino acids such as phenylalanine, tryptophan, and tyrosine.[7] Peptides may be further digested by other proteases (in the duodenum) and eventually absorbed by the body. Pepsin is stored as pepsinogen so it will only be released when needed, and does not digest the body's own proteins in the stomach's lining.

Pepsin functions best in acidic environments and is often found in an acidic environment, particularly those with a pH of 1.5 to 2.[8] Pepsin denatures if the pH is more than 5.0.

Pepsin is said to have an optimum temperature between 37°C and 42°C in humans.[9]

Pepsin is potently inhibited by the peptide inhibitor pepstatin. Pepsin is used for digestion of proteins.

Storage

Pepsins should be stored at very cold temperatures (between −20°C and −80°C) to prevent autolysis (self-cleavage). Autolysis may also be prevented by storage of pepsins at pH 11 or by using modified pepsins (e.g., by reductive methylation). When the pH is adjusted back to 6.0 activity returns.

See also

References

  1. ^ PDB 1PSO; Fujinaga M, Chernaia MM, Tarasova NI, Mosimann SC, James MN (May 1995). "Crystal structure of human pepsin and its complex with pepstatin". Protein Sci. 4 (5): 960–72. doi:10.1002/pro.5560040516. PMID 7663352. 
  2. ^ Florkin M (March 1957). "[Discovery of pepsin by Theodor Schwann.]" (in French). Rev Med Liege 12 (5): 139–44. PMID 13432398. 
  3. ^ Asimov, Isaac (1980). "page 95". A short history of biology. Westport, Conn: Greenwood Press. ISBN 0-313-22583-4. 
  4. ^ Northrop JH (May 1929). "Crystalline pepsin". Science (journal) 69 (1796): 580. doi:10.1126/science.69.1796.580. PMID 17758437. 
  5. ^ "Enzyme entry 3.4.23.1". http://www.expasy.org/cgi-bin/nicezyme.pl?3.4.23.1. Retrieved 2008-12-14. 
  6. ^ Cox, Michael; Nelson, David R. (2008). "page 96". Lehninger Principles of Biochemistry (Fifth ed.). San Francisco: W. H. Freeman. ISBN 0-7167-7108-X. 
  7. ^ Cox, Michael; Nelson, David R. (2008). "page 675". Lehninger Principles of Biochemistry (Fifth ed.). San Francisco: W. H. Freeman. ISBN 0-7167-7108-X. 
  8. ^ "Enzymes Enzymes". http://www.innvista.com/HEALTH/nutrition/diet/enzymes.htm Enzymes. Retrieved 2008-12-14. 
  9. ^ "BRENDA: Entry of pepsin A (EC-Number 3.4.23.1 )". http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.23.1. Retrieved 2008-12-14. 

External links



Translations: Pepsin
Top

Dansk (Danish)
n. - tale, der skal sætte liv i foretagendet

Nederlands (Dutch)
pepsine

Français (French)
n. - pepsine

Deutsch (German)
n. - (Chem.) Pepsin

Ελληνική (Greek)
n. - (βιολ.) πεψίνη

Italiano (Italian)
pepsina

Português (Portuguese)
n. - pepsina (f)

Русский (Russian)
пепсин

Español (Spanish)
n. - pepsina

Svenska (Swedish)
n. - pepsin (kem.)

中文(简体)(Chinese (Simplified))
胃液素

中文(繁體)(Chinese (Traditional))
n. - 胃液素

한국어 (Korean)
n. - 펩신(위액 속에 있는 단백질 분해 효소), 펩신제

日本語 (Japanese)
n. - ペプシン

العربيه (Arabic)
‏(الاسم) ببسين : مادة كيماويه تساعد على الهضم‏

עברית (Hebrew)
n. - ‮אנזים-עיכול, פפסין‬


 
 

 

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