Digestion occurs in all mammals, including human beings. There are multiple steps involved in the breaking down of food, each of which is related to specific digestive enzymes. Some of these are found in the mouth, while others are found in the intestines. Pepsin is a material that has its own unique function in the digestion of food.
Pepsin is a digestive enzyme that is released in the stomach as pepsinogen. The release of hydrochloric acid stimulates the release of this basic form of pepsin. When pepsinogen is exposed to the hydrochloric acid in the stomach, the pepsinogen unfolds and breaks into pepsin.
The main function of pepsin is to break down proteins that are found in foods such as meat and eggs into smaller pieces (polypeptides). It breaks down proteins only at certain points, so the protein is not digested completely to the amino acid level. In order for that to occur, the food has to pass into the intestines, where other enzymes complete the digestion process.
One misconception that involves pepsin is the idea that hydrochloric acid is what breaks down food in the stomach. In reality, hydrochloric acid does two things. First, it changes the shape of the protein bonds---this is called denaturization. This leaves the protein bonds exposed. Secondly, hydrochloric acid causes pepsinogen to be transformed into pepsin. With the protein bonds exposed and a supply of pepsin present in the stomach, the proteins then can be broken into polypeptides. Hydrochloric acid thus promotes digestion but does not actually break down food proteins.
Antacids and Pepsin Function
Pepsin requires a low pH level in order to function. Antacids, however, raise the pH level of the gastric juices to a level that is not optimal for pepsin to work. Since pepsin is needed in order to break down proteins into polypeptides, those who take over-the-counter or prescription antacids actually may be doing more harm than good in that they may be hindering part of the digestive process. Additionally, it is thought that some food allergies are related to partially digested proteins passing through the intestinal wall. Since antacids decrease the effectiveness of pepsin, thereby increasing the number of partially digested proteins that can pass through to the intestine, it may be that antacids actually may increase the risk of food allergy development.
Pepsin was discovered in 1836 by Theodor Schwann. It was not crystallised until nearly a century later in 1929. When it finally was crystallised, the crystallisation was done by scientist John Northrop.