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Pepsin is expressed as a zymogen called pepsinogen, whose primary structure has an additional 44 amino acids compared to the active enzyme. In the stomach, gastric chief cells release pepsinogen. This zymogen is activated by hydrochloric acid (HCl), which is released from parietal cells in the stomach lining.
Pepsin is the main gastric enzyme. 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.
Gastric acid or stomach acid is the acidic component – hydrochloric acid of gastric juice, produced by parietal cells in the gastric glands of the stomach lining. In humans, the pH is between one and three, much lower than most other animals, but is very similar to that of carrion eating carnivores , needing protection from ingesting pathogens .
A prime example of this is pepsin, which is secreted in the stomach by chief cells. Pepsin in its secreted form is inactive . However, once it reaches the gastric lumen it becomes activated into pepsin by the high H+ concentration, becoming an enzyme vital to digestion. The release of the enzymes is regulated by neural, hormonal, or paracrine ...
The gastric hydrogen potassium ATPase or H + /K + ATPase is the proton pump of the stomach.It exchanges potassium from the intestinal lumen with cytoplasmic hydronium [2] and is the enzyme primarily responsible for the acidification of the stomach contents and the activation of the digestive enzyme pepsin [3] (see gastric acid).
The stomach is also called the gaster (Greek belly) or venter from which we have the adjective gastric applied to structures related to the organ. [3] The stomach is a muscular, hollow organ in the upper gastrointestinal tract of humans and many other animals, including several invertebrates.
The gastric mucosa is covered in surface mucous cells that produce the mucus necessary to protect the stomach's epithelial lining from gastric acid secreted by parietal cells in the glands, and from pepsin, a secreted digestive enzyme. Surface mucous cells follow the indentations and partly line the gastric pits.
In mammals, HCl is secreted into the stomach by parietal cells, while chief cells secrete pepsinogen. [7] In birds, the gastric glands of the proventriculus secrete both the HCl and the pepsinogen. [8] Since pepsinogen is a zymogen, it is then activated to pepsin by the HCl.