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Pepsin / ˈ p ɛ p s ɪ n / is an endopeptidase that breaks down proteins into smaller peptides and amino acids. It is one of the main digestive enzymes in the digestive systems of humans and many other animals, where it helps digest the proteins in food. Pepsin is an aspartic protease, using a catalytic aspartate in its active site. [2]
It is produced in the stomach by gastric chief cells in its inactive form pepsinogen, which is a zymogen. Pepsinogen is then activated by the stomach acid into its active form, pepsin. Pepsin breaks down the protein in the food into smaller particles, such as peptide fragments and amino acids.
Proteolysis in organisms serves many purposes; for example, digestive enzymes break down proteins in food to provide amino acids for the organism, while proteolytic processing of a polypeptide chain after its synthesis may be necessary for the production of an active protein.
The enzyme is first made in the inactive form, pepsinogen by chief cells in the lining of the stomach. [24] With an impulse from the vagus nerve, pepsinogen is secreted into the stomach, where it mixes with hydrochloric acid to form pepsin. [25] Once active, pepsin works to break down proteins in foods such as dairy, meat, and eggs. [24]
Ribbon diagram of a protease (TEV protease) complexed with its peptide substrate in black with catalytic residues in red.(. A protease (also called a peptidase, proteinase, or proteolytic enzyme) [1] is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. [2]
Chyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins. Gastric juice in the stomach also contains pepsinogen. Hydrochloric acid activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides.
The proenzyme Pepsinogen, with the exposure to hydrochloric acid gets converted into the active enzyme pepsin, the proteolytic enzyme of the stomach. Hydrochloric acid (HCl) provides the acidic pH (pH 1.8) optimal for pepsins. Rennin is a proteolytic enzyme found in gastric juice of infants which helps in the digestion of milk proteins.
The gastric chief cell (also known as a zymogenic cell or peptic cell) is a cell in the stomach that releases pepsinogen [1] and chymosin. Pepsinogen is activated into the digestive enzyme pepsin when it comes in contact with hydrochloric acid produced by gastric parietal cells. [2]