pepsin(redirected from pepsin A)
Also found in: Dictionary, Thesaurus, Encyclopedia.
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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
A group of closely related aspartic proteinases. Pepsin A is the principal digestive enzyme of gastric juice, formed from pepsinogen; it hydrolyzes peptide bonds at low pH values (is alkali-labile), preferably adjacent to phenylalanyl and leucyl residues, thus reducing proteins to smaller molecules (referred to as proteoses and peptones); pepsin B (gelatinase) is similar to pepsin A, but formed from porcine pepsinogen B and has a more restricted specificity; pepsin C (gastricsin is human pepsin C) is also similar to pepsin A, and structurally related to it, having a more restricted specificity.
[G. pepsis, digestion]
Farlex Partner Medical Dictionary © Farlex 2012
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.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.
pepsinA generic term for any of the gastric proteases that are released by gastric chief cells as proenzymes (pepsinogen).
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.
The enzyme produced by the stomach for the digestion of protein.
[G. pepsis, digestion]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
pepsinA digestive ENZYME whose precursor PEPSINOGEN is secreted by cells in the stomach lining. Pepsin breaks down protein to PEPTIDES. See also PEPTIDASE.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
pepsinan enzyme secreted in the inactive form PEPSINOGEN by chief or peptic cells in the gastric pits of the stomach of vertebrates, and which breaks down proteins in acid solution into short polypeptide chains which are subsequently broken down further by PEPTIDASES.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005