where is pepsin secreted in the digestive system
stomach
title: Pepsin text: in its active site. It is one of three principal proteases in the human digestive system, the other two being chymotrypsin and trypsin. During the process of digestion, these enzymes, each of which is specialized in severing links between particular types of amino acids, collaborate to break down dietary proteins into their components, i.e., peptides and amino acids, which can be readily absorbed by the small intestine. Pepsin is most efficient in cleaving peptide bonds between hydrophobic and preferably aromatic amino acids such as phenylalanine, tryptophan, and tyrosine. Pepsin's proenzyme, pepsinogen, is released by the chief cells in the stomach title: Pepsin text: Pepsin Pepsin is an endopeptidase that breaks down proteins into smaller peptides (that is, a protease). It is produced in the stomach and 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 has a three-dimensional structure, of which one or more polypeptide chains twist and fold, bringing together a small number of amino acids to form the active site, or the location on the enzyme where the substrate binds and the reaction takes place. Pepsin is an aspartic protease, using a catalytic aspartate title: Pepsin text: one of the first enzymes to be crystallized when John H. Northrop crystallized it using dialysis, filtration, and cooling. Pepsin is expressed as a zymogen called 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 title: Exoenzyme text: plant-derived products. Discovered in 1836, pepsin was one of the first enzymes to be classified as an exoenzyme. The enzyme is first made in the inactive form, pepsinogen by chief cells in the lining of the stomach. With an impulse from the vagus nerve, pepsinogen is secreted into the stomach, where it mixes with hydrochloric acid to form pepsin. Once active, pepsin works to break down proteins in foods such as dairy, meat, and eggs. Pepsin works best at the pH of gastric acid, 1.5 to 2.5, and is deactivated when the acid is neutralized to a pH of 7. title: Proventriculus text: Proventriculus The proventriculus is part of the digestive system of birds. An analogous organ exists in invertebrates and insects. The proventriculus is a standard part of avian anatomy, and is a rod shaped organ, located between the oesophagus and the gizzard of most birds. It is generally a glandular part of the stomach that may store and/or commence digestion of food before it progresses to the gizzard. The primary function of the proventriculus is to secrete Hydrochloric acid and Pepsinogen into the digestive compartments that will churn the ingested material through muscular mechanisms. Pepsinogen produces pepsin, which breaks the peptide