Question

Write the main function of pepsin.

Answer 1

Pepsin is an enzyme (endopeptidase – proteolytic enzyme) that is produced in the lining of the stomach by specialized chief cells. It is one of the most important digestive enzymes of the human digestive system. It is present in many other animals also.

Complete answer:
Pepsin is an active form of enzyme pepsinogen and is present in gastric juice. Pepsinogen is secreted by the chief cells of the stomach wall, and in the acidic environment (in the presence of hydrochloric acid from the gastric juice), it gets activated and converts into pepsin. The pH should be in the range of 1.5-2.5 for its activation. Pepsin was discovered by a German physiologist Theodor Schwann in the year 1836.

Pepsin helps in digestion of proteins found in food particles. Pepsin is an aspartic protease, which means it is a protease enzyme and uses water molecules that are bound to aspartate for catalysing the peptides.

There are three proteases found in the digestive system of humans - pepsin, trypsin and chymotrypsin. The role of these specialized enzymes is seen during the process of digestion where they break the bonds between dietary proteins, and convert them into peptides and amino acids, which are easy to absorb by the intestine. Pepsin mainly hydrolyses tryptophan, phenylalanine and tyrosine.

Once the proteins present in the food get partially degraded into peptides, it passes to the intestine from where it either gets absorbed into the blood or is further degraded or broken down with the help of the enzymes present in the pancreas.

Note: Small amount of pepsin is also present in the bloodstream. When partially digested protein is absorbed into the blood from the intestine, pepsin further breaks it down as well. Protein is mainly found in food products having milk or dairy products, eggs, meat, etc.