What makes pepsin

Parietal cells of the gastric wall release hydrochloric acid HCl , pepsinogen can be activated by hydrochloric acid. Gastrin and vagus nerves trigger the release of pepsinogen and hydrochloric acid from the gastric wall when eating. Hydrochloric acid produces acidic environment, which makes pepsinogen unfold and cleave in an autocatalytic manner, thus producing pepsin.

Pepsin cuts 44 amino acids in pepsinogen into more pepsin. Pepsin is a chain protein monomer composed of two similar folding domains separated by a deep cleft. The catalytic site of pepsin is formed at the junction of the domain, each domain contains two aspartic acid residues, Asp32 and Asp Under the catalysis of pepsin, the water molecule helps the active carboxyl group to bear positive and negative charges with aspartic acid and aspartic acid 32, respectively, which breaks the peptide bond in the protein.

The activity of pepsin was the highest in pH2. Therefore, in the solution below pH8. The stability of pepsin at high pH value is of great significance to the diseases caused by pharynx and larynx reflux. Pepsin is one of the main causes of mucosal injury in pharynx and larynx reflux. Pepsin still stays in the pharynx and larynx after pharyngeal reflux. Although the enzyme is in a neutral environment, it can be reactivated in the subsequent acid reflux event.

After pepsin is activated, laryngeal mucosa is exposed to active pepsin, resulting in a decrease in the expression of protective proteins, thus increasing the susceptibility to laryngeal injury. In addition, pepsin may also cause mucosal damage in weak acid or non-acid reflux events.

Pepsins are synthesized as inactive pre-proenzymes, consisting of a signal peptide, activation peptide and active enzyme. The signal peptide is cleaved as the protein is inserted into endoplasmic reticulum and the resulting proenzyme - pepsinogen - is transported to the Golgi and condensed into secretory granules.

Pepsinogens are secreted in a form such that the activation peptide assumes a compact structure that occludes the active site. On exposure to an acidic pH the activation peptide is cleaved, thereby unmasking the active site and generating catalytically-active pepsin. Retrieved Current Protocols in Protein Science. Chapter Unit ISBN A short history of biology. Westport, Conn: Greenwood Press. Online Etymology Dictionary. The Quarterly Review of Biology. JSTOR Bibcode : Sci Lehninger principles of biochemistry.

San Francisco: W. ISBN X. The Laryngoscope. The Annals of Otology, Rhinology, and Laryngology. Journal of Gastrointestinal Surgery. The American Journal of Gastroenterology. Gastroesophageal and pharyngeal reflux detection using impedance and hour pH monitoring in asymptomatic subjects: defining the normal environment. J Gastrointest Surg ;— Otolaryngology—Head and Neck Surgery.

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World Scientific Publishing Company. PDB builds introductory materials to help beginners get started in the subject "", as in an entry level course as well as resources for extended learning.

Toggle navigation PDB Educational portal of. Molecule of the Month. Pepsin Pepsin digests proteins in strong stomach acid Pepsin top and pepsinogen bottom. During the holiday season, we often place greater demands on our digestive enzymes than at other times of the year. Our digestive system contains a host of tough, stable enzymes designed to seek out those rich holiday treats and break them into small pieces. Pepsin is the first in a series of enzymes that digest proteins.

In the stomach, protein chains bind in the deep active site groove of pepsin, seen in the upper illustration from PDB entry 5pep , and are broken into smaller pieces. Then, a variety of proteases and peptidases in the intestine finish the job. The small fragments--amino acids and dipeptides--are then absorbed by cells for use as metabolic fuel or construction of new proteins.

Enzymes that digest proteins pose a real challenge. The enzyme must be constructed inside the cell, but controlled in some manner so that it doesn't immediately start digesting the cell's own proteins. To solve this problem, pepsin and many other protein-cutting enzymes are created as inactive "proenzymes," which may then be activated once safely outside the cell.