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In the body, pepsin is an endopeptidase enzyme, which means it breaks down proteins into peptides. As a digestive enzyme, it is produced by the main cells of the stomach lining and is one of the most important in the digestive systems of humans and many other animals, where it aids in the digestion of protein. It is an aspartic protease with an active site that contains the amino acid aspartate as the catalytic aspartate.

It is one of three major proteases found in the human digestive system, the other two being chymotrypsin and trypsin, and it is involved in the digestion of proteins.This group of enzymes works together to break down dietary proteins into their constituent parts, which are peptides and amino acids, which can be easily absorbed by the small intestine.

Each enzyme is specialised in breaking down specific types of amino acids, and they all work together to break down dietary proteins into their constituent parts. Pepsin has a broad range of cleavage specificities, however particular amino acids, such as tyrosine, phenylalanine, and tryptophan, increase the likelihood of cleavage by the enzyme. Gastric chief cells in the stomach wall release pepsinogen, a proenzyme that when combined with the hydrochloric acid in the gastric juice activates to form pepsin.

 Pepsin is a digestive enzyme that is produced by the stomach wall.

Pepsin’s molecular structure

Pepsin is a monomer (chain protein) composed of two folding domains that are separated by a deep cleft. Pepsin is a digestive enzyme that is produced by the digestive enzyme pepsin. 

It is at the domain junction where the catalytic site of pepsin is generated, with two aspartic acid residues, Asp32 and Asp215, in each domain, serving as the catalyst. 

Because the water molecule allows the active carboxyl group to bear positive and negative charges with aspartic acids 215 and 32, respectively, it aids in the catalysis of pepsin’s catalysis, which results in the breakage of the peptide bond in the protein.

Formula

Applications

  1. Among the most popular applications for pepsin is the generation of F(ab’)2 fragments from antibodies.
  2.  Using only the antigen-binding (Fab) part of the antibody is desirable in several experiments because it is more sensitive. 
  3. Antibodies can be enzymatically digested to create either a F(ab’)2 fragment of the antibody or a Fab fragment of the antibody for use in these applications. 
  4. Using pepsin, IgG is digested to yield a F(ab’)2 fragment, which is formed by cleaving the heavy chains around the hinge region of the antibody.
  5. Due to one or more of the disulfide connections that connect the heavy chains in the hinge region remaining intact, the antibody’s two Fab regions remain connected together, resulting in a divalent molecule (containing two antibody binding sites), which is designated by the abbreviation F(ab’). 
  6. The light chains are still joined to the heavier chain and are not damaged.
  7. The Fc fragment is degraded into tiny peptides after being exposed to heat. Instead of pepsin, papain is used to cleave IgG into Fab fragments. This method is more efficient. Specifically, papain cleaves IgG just above the hinge region, which contains the disulfide bonds that join the heavy chains, but just below the site of the disulfide bond that connects the light chain and heavy chain.

Papain cleaves IgG in two ways. 

Two independent monovalent (having a single antibody binding site) Fab fragments and an intact Fc fragment are produced as a result of this procedure.

By using a technique such as chromatography, you may separate the fragments from the rest of the mixture.

Function of Pepsin

  1. Pepsin is a proteolytic enzyme that is produced by specialised cells in the stomach known as chief cells, which are responsible for digestion.
  2.  It is a strong enzyme found in gastric juice that aids in the digestion of proteins.It aids in the digestion process. It degrades big polypeptides into smaller peptide fragments, which are then recycled.
  3. Eggs, beef, seeds, and other dairy products are examples of dietary proteins that can be broken down.

Conclusion

It is estimated that pepsin concentrations in the stomach range between 0.5 and 1 mg/mL in individuals. Despite the fact that pepsin is inactive at pH values of 6.5 and above, it is still active  until pH values of 8.0 and higher.Therefore, re-acidification will cause pepsin to be activated in solutions with pH values as high as 8.0. It is crucial to note that the safety of pepsin at high pH has important implications for laryngopharyngeal reflux illness. 

Pepsin is found in the larynx after a case of gastric reflux has occurred. 

The enzyme pepsin will be dormant at the mean pH of the laryngopharynx (pH = 6.8), but it may be reactivated during subsequent acid reflux episodes, causing tissue damage in the surrounding area. Pepsin is capable of breaking a wide variety of proteins.