What is Pepsin?


is an


in the stomach that is responsible for breaking down of proteins. It is one of the three main proteolytic enzymes in the digestive system, the other two being chymotrypsin and trypsin.

Theodor Schwann

discovered pepsin in 1836 and coined its name from the greek word


which means digestion. Later in 1930 John H. Northrop, of the Rockefeller Institute of Medical Research, crystallized pepsin and established its protein nature.

Pepsin in stomach:

Pepsinogen is a pro-form zymogen of pepsin. It is released in the stomach by its chief cells. This zymogen is activated by hydrochloric acid released from parietal cells in the stomach linings. Gastrin is the hormone that triggers the release of pepsinogen and also controls the secretion of hydrochloric acid from the stomach lining. This happens when food is ingested. Pepsinogen wants acidic environment which is created by the hydrochloric acid. Upon exposure to hydrochloric acid pepsinogen unfolds and breaks into pepsin.

Function of pepsin:

Pepsin’s main function is to break down proteins that are found in protein rich foods such as meat, eggs etc. It breaks them into smaller pieces called polypeptides. Interesting thing about pepsin is that it breaks proteins only at certain points so that the protein is not digested completely to the amino acid level. For this to occur, the food needs to pass to the intestines where other enzymes complete the digestion process.

Nature of Pepsin:

Pepsin functions in acidic environment with pH of 1.5 to 2. Pepsin gets denatured if the pH is more than 5.0.

Pepsin needs optimum temperature of range 37 degree C to 42 degree C (ideal temperature in the human body). It is potently inhibited by the peptide inhibitor pepstatin.

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