Pepsin: Wikis

Advertisements
  

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

Encyclopedia

From Wikipedia, the free encyclopedia

pepsin A
1PSO.png
Pepsin in complex with pepstatin.[1]
Identifiers
EC number 3.4.23.1
CAS number 9001-75-6
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures
Gene Ontology AmiGO / EGO
pepsin B
Identifiers
EC number 3.4.23.2
CAS number 9025-48-3
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures

Pepsin is an enzyme whose precursor form (pepsinogen) 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 4.0 activity returns.

Genes

The following three genes encode identical human pepsin enyzmes:

pepsinogen 3, group I (pepsinogen A)
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


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 (inactive 2009-12-24). 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-enzymes: 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

Advertisements

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

PEPSIN, an enzyme or ferment obtained by drying the mucous lining of the fresh and healthy stomach of a pig, sheep or calf. As used in medicine it consists of a light yellow-brown or white powder or of pale yellow translucent grains or scales. It is only slightly soluble in water and alcohol. Pepsin is used to help gastric digestion in old people and in those in whom there is a deficient secretion of the gastric juice. It is useful in chronic catarrhal conditions of the stomach, the dyspepsia of alcoholism, and in gastric ulcer and cancer of the stomach.

Pepsin digests the albumens but is useless in the digestion of fats or carbohydrates. It may also be used to predigest albuminous foods. The following is a method of peptonizing beef. Take a lb of minced raw lean beef, a pint of water containing 0.2% of hydrochloric acid, place in a jar with 30 grs. of pepsin, set in a warm place at Ito° F. for 3 hours, stirring occasionally. Then quickly boil it. It is usually unnecessary to strain it, as the meat is reduced to a fine almost impalpable powder which is readily assimilated. Many varieties of proprietary peptonizing tablets are on the market and are convenient for the preparation of peptonized milk. The following is a method of preparing it. Take a clean glass quart bottle, pour in a pint of perfectly fresh cold milk, then add a teacupful of cold water in which a peptonizing tablet has been dissolved. Submerge the bottle in a can of water at Ioo° F. for from 5 to Jo minutes, take out the bottle and place on ice to prevent the further action of the pepsin. If no ice is convenient bring the milk to a boil for the same purpose. If the action of the pepsin be continued for a much longer period the milk becomes bitter to the taste from the development of excess of peptones. Predigested foods should not be used over a long period or the digestive functions of the stomach may atrophy from disuse.

Pancreatic solution, derived from the pancreas of a pig digested in alcohol, has the power of converting starch into sugar, and albumen and fibrin into peptones. It only acts in an alkaline medium and at a temperature under 140° F. If used to peptonize milk sodium bicarbonate should be added. Many commercial preparations are on the market. Trypsin, the principal ferment of the pancreas, also changes proteids into peptones.


<< Pepper Tree

John Christopher Pepusch >>


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

German

Noun

Pepsin n.

  1. pepsin (digestive enzyme)

This German entry was created from the translations listed at pepsin. It may be less reliable than other entries, and may be missing parts of speech or additional senses. Please also see Pepsin in the German Wiktionary. This notice will be removed when the entry is checked. (more information) December 2009


Simple English

Pepsin is a kind of enzyme. It acts on proteins in the stomach. It works best at a pH of about 1.5.[1] It will not work at a pH above 6.

It was the first animal enzyme to be discovered. Theodor Schwann discovered it in 1836.

Pepsin is used to make cheese. The brand name Pepsi comes from pepsin.

References



Advertisements






Got something to say? Make a comment.
Your name
Your email address
Message