- Pepsin
Protbox
Name= Pepsin
Photo= 1PSO.png
Caption= Pepsin in complex withpepstatin
Gene = 8885 (HGNCid)
Type =protease
Functions =digestion
ECnumber=3.4.23.1
Names = Pepsinogen
Interactions = pepstatin
Pages =Pepsin is a digestive
protease (EC number|3.4.23.1) released by the chief cells in thestomach that functions to degrade foodprotein s intopeptides .According to American Heritage Dictionary, pepsin derives from the Greek word "pepsis", meaning
digestion ("peptein": to digest).Pepsin was discovered by
Theodor Schwann [cite journal |author=Florkin M |title=Discovery of pepsin by Theodor Schwann. |journal=Rev Med Liege |volume=12 |issue=5 |pages=139–44 |year=1957 |pmid=13432398] in1836 . It was the first animalenzyme to be discovered. In 1929, it became one of the first enzymes to be crystallized, byJohn H. Northrop .Precursor
Pepsin is expressed as a pro-form
zymogen , pepsinogen, whoseprimary structure has an additional 44 amino acids.In the stomach,
chief cell s release pepsinogen. This zymogen is activated byhydrochloric acid (HCl), which is released fromparietal cell s in the stomach lining. The hormonegastrin and thevagus nerve trigger the release of bothpepsinogen 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 anautocatalytic 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 C-terminal of aromatic amino acids such asphenylalanine andtyrosine although it has broad specificity. It will not cleave at bonds containingvaline ,alanine , orglycine . Peptides may be further digested by other proteases (in theduodenum ) 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 [ [http://www.innvista.com/HEALTH/nutrition/diet/enzymes.htm Enzymes ] ] .
Pepsin is said to have an optimum temperature between 37°C and 42°C in humans [ [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.23.1 BRENDA: Entry of pepsin A(EC-Number 3.4.23.1 ) ] ] .
ee also
Other important digestive proteases are the pancreatic enzymes
trypsin andchymotrypsin .Pepsin denatures if the pH is more than 5.0. Pepsin is potently inhibited by the peptide inhibitorpepstatin ."Pepsin" was the common named for pepsin chewing gum, a popular digestive aid composed of gum and pepsin enzymes extracted from butchered hog stomachs. Dr. Eugene Beeman first introduced the product in 1891.
It is disputed whether or not the original recipe for "
Pepsi " includedenzyme pepsin. [ [http://medialit.med.sc.edu/pepsi.htm Mike Gange, "Pop Culture Paraphernalia"] , "The Encyclopedia of Pepsi-Cola Collectibles"] [ [http://inventors.about.com/library/inventors/blpepsi.htm "The History of Pepsi Cola"] , Mary Bellis, "about.com"]torage
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 pepsins modified by e.g. reductive methylation. When the pH is adjusted back to pH 6 activity returns.
Outside links
* [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.23.1 Pepsin A description from BRENDA database]
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