Pepsin (Gr. Pepsis - Digestion)

Pepsin is a proteolytic enzyme secreted by the chief cells of the gastric mucosa. It breaks down proteins into peptides and amino acids, which is necessary for further digestion and absorption of food.

Pepsin is active only in the acidic environment of the stomach and has an optimum action at a pH of about 2. Such low acidity in the stomach is created by hydrochloric acid, which is produced by the parietal cells of its mucous membrane. When the pH rises above 5, pepsin loses activity.

Thus, pepsin plays a critical role in the digestion of protein foods, being one of the key enzymes of gastric juice. Its optimal action in the acidic environment of the stomach ensures effective hydrolysis of proteins in the early stages of digestion.