Is Pepsin an Enzyme: 9 Facts You Should Know!

In this article we are focusing on the topic entitled as “Is Pepsin an Enzyme: 9 Facts You Should Know”, giving the details and the explained statements supporting the given topic.

Pepsin is an enzyme that belongs to the endopeptidase class of enzymes. The substrates for these enzymes are proteins. Pepsin catalyzes the breakdown of the large proteins into its smaller subunits called amino acids. This is an enzyme produced in the stomach from gastric chief cells which lies in the lining of the stomach.

There are different types of enzymes that are present inside the cells of living organisms, each performing its own significant functions necessary for the cell function. Pepsin is a type of degradative enzyme which catalyzes the reactions involving degradation and are present in the low pH environment inside the stomach.

Structure of pepsin enzyme

The structure of pepsin is composed of two lobes and harbors two N and C domains. Pepsin is consisting of 326 amino acid residues, the N-terminal is composed of first 175 residues ad the rest is constituted by the C-terminal. The structure of pepsin enzyme is predominantly made of beta pleated sheets and also contains alpha helices.

Pepsin undergoes denaturation at alkaline pH (6-7 range) and once it is denatured it cannot be activated even after renaturation as it loses its active site. Pepsin belongs to the class of endopeptidase enzymes which are involved in catalyzing biochemical reactions where a complex molecule is broken down into its constitutive units.

is pepsin an enzyme
Pepsin structure from PDB file Image from Wikipedia

Functions of pepsin enzyme

Pepsin is a type of protease enzyme which helps in degrading proteins into smaller units. It is secreted by the chief cells present in the inner lining of stomach in an inactive zymogen form known as pepsinogen. After being produced into the stomach it is exposed to the acid environment present in the stomach and becomes active.

Pepsin is produced naturally inside the stomach in animals including humans and is also produced on a large scale commercially for industrial purpose. It is used in the manufacturing of food, in leather industries and in the research field. Proteins help in the conversion of proteins into peptones and proteoses.

Catabolic Pathway Image from Wikipedia

Types of Digestive Enzymes

EnzymeSite of releaseRole
Salivary amylaseMouthBreak down starch into glucose
Pancreatic amylaseSmall intestineDegrade carbohydrates
PepsinstomachBreaks down proteins into amino acids
TrypsinpancreasBreaks peptide bonds
PeptidasesSmall intestineCleave peptides
NucleaseSmall intestineCleaves phosphodiester bonds
LipaseSmall intestineBreaks down lipids and fats present in food
Types of Digestive Enzymes
The Digestive system Image from Wikipedia

Why is pepsin an enzyme?

Pepsin is an enzyme is proved by the way it functions. Pepsin is one of the catabolic enzymes that split down the complex proteins into individual amino acids by breaking down the peptide bonds which links the amino acids together to form a protein.

The chief cells in the stomach produce pepsin in the form of an inactive zymogen known as pepsinogen. Hydrochloric acid (HCL) is present inside the stomach and makes the environment inside acidic which is helpful in digestion of food rich in proteins and carbohydrates. A lower pH helps in the activation of pepsin enzyme and stimulates its function.

How is pepsin an enzyme?

Pepsin is an enzyme in so many ways, the first instance is its function as an endopeptidase where it digests protein and breaks it down to smaller units of amino acids. Pepsin has been known to be produced by the chief cells which are found in the inner lining of stomach. Pepsin is one of the important digestive enzymes in humans and other animals.

Pepsin is referred as an acid protease present in the stomach and is evidently the first animal enzyme to be discovered. The inactive form of pepsin called pepsinogen is converted into the active form pepsin in the presence of hydrochloric acid which is released by stomach parietal cells.

What group of enzymes is pepsin?

A class of enzymes known as endopeptidase consists of the catabolic proteins. Proteins that break down complex proteins into its smaller subunits called amino acids. Pepsin is one kind of endopeptidase that works on the proteins in the acidic environment of the stomach.

Pepsin is highly significant enzyme as it helps in the digestion of the food, we intake. Pepsin is highly known for its action as a protease, however there are several other enzymes that participate in the digestion of food along with pepsin. Pepsin is also known as an acidic protease, which is the first enzyme to be discovered of this kind. Pepsinogen is called the inactive form of pepsinogen.

Where is pepsin enzyme found?

Pepsin is found in the acidic environment of stomach where it serves as a digestive enzyme for the proteins consumed in the diet. It is secreted as an inactive enzyme called pepsinogen by the gastric chief cells. The acidic environment inside the stomach is maintained by the parietal cell which continuously produce HCL to lower the pH (around 1.5 to 2) for the activation of protein.

Pepsin is majorly found in the gastric juice. There are several other digestive enzymes such as lipases, proteases, and amylases which are produced by the pancreas and then moved into the small intestine after food ingestion.

Can pepsin be a substrate?

No, pepsin cannot be a substrate. The proteins present in the food are the substrates for the pepsin enzyme to act upon and releases the amino acids and small peptides as the end products. Pepsin is a protein degrading enzyme also known as protease which helps in cleaving the proteins into two products proteoses and peptones. Pepsin becomes activated in the presence of acid, mainly HCL is involved in the activation of pepsin.

Pepsin is a type of endoenzyme which is defined as the enzyme produced intracellularly. Intracellular enzymes are produced inside the cells where they perform their function. For examples, pepsin is produced by the chief cells inside the stomach and the trypsin is produced in the pancreas.

Is pepsin enzyme a protein?

Yes, pepsin indeed a protein. All enzymes are proteins, pepsin is released as zymogen pepsinogen which is an inactive protein. Pepsin is involved in various biochemical processes, mainly catabolic reactions that involves the release of large amount of energy that is used by the cells to perform variety of functions. Examples of catabolic enzymes involved, pepsin, amylase, trypsin, etc.


To conclude the article, we can say that pepsin is a central digestive enzyme, which is also a protein and is produced by the chief cells of the stomach and plays a role in degrading proteins into small stretches of amino acids.

Sneha Sah

Hey! I am Sneha Sah, I have completed post graduation in Biotechnology. Science has always been fascinating to me and writing is my passion. As an academic writer my aim is to make Science easy and simple to learn and read. Reach me at-

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