Dictionary:

pepsin

  (pĕp'sĭn)

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.]

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.

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.

For more information on pepsin, visit Britannica.com.

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.

Pepsin
Pepsin in complex with pepstatin
Other names:	Pepsinogen
Genetic data
Gene code:	8885 (HGNCid)
Protein Structure/Function
Protein type:	protease
Functions:	digestion
Other
Molecular interactions:	pepstatin
Database Links
EC number:	3.4.23.1

Pepsin is a digestive protease (EC 3.4.23.1) released by the chief cells in the stomach that functions to degrade food proteins into peptides.

According to American Heritage Dictionary, pepsin derives from the Greek word pepsis, meaning digestion (peptein: to digest).

Pepsin was discovered by Theodor Schwann^[1] in 1836. It was the first animal enzyme to be discovered.

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. HCl 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 of aromatic amino acids such as phenylalanine and tyrosine. It will not cleave at bonds containing valine, alanine or glycine. 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, particularly those in a pH of 3.

See also

Other important digestive proteases are the pancreatic enzymes trypsin and chymotrypsin. Pepsin denatures if the pH is more than 5.0. Pepsin is potently inhibited by the peptide inhibitor pepstatin.

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 pepsins modified by e.g. reductive methylation. When the pH is adjusted back to pH 6 activity returns.

External links

• Pepsin A description from BRENDA database
• MeSH Pepsin+A
• MeSH Pepsinogens
• MeSH Pepsinogen+A
• MeSH Pepsinogen+C

References

1. ^ Florkin M (1957). "Discovery of pepsin by Theodor Schwann.". Rev Med Liege 12 (5): 139-44. PMID 13432398. 

Digestive system, physiology: gastrointestinal physiology
Enteric nervous system	Meissner's plexus - Auerbach's plexus
Exocrine	Chief cells (Pepsinogen) - Parietal cells (Gastric acid, Intrinsic factor) - Goblet cells (Mucus)
Endocrine/paracrine	G cells (gastrin), D cells (somatostatin) - ECL cells (Histamine) - enterogastrone: I cells (CCK), K cells (GIP), S cells (secretin)
Border	Brunner's glands - Paneth cells - Enterocytes
Fluids	Saliva - Bile - Intestinal juice - Gastric juice - Pancreatic juice
Processes	Swallowing - Vomiting - Peristalsis (Interstitial cell of Cajal) - Migrating motor complex - Borborygmus - Gastrocolic reflex - Segmentation contractions - Defecation

Proteases: aspartic acid proteases (EC 3.4.23)
Vertebrate	Pepsin - Chymosin - Renin - Signal peptide peptidase - Beta secretase
Pathogenic	Plasmepsin - HIV-1 protease

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

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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