Pepsin is a digestive enzyme that breaks down proteins in the stomach. This digestive enzyme is created as pepsinogen in the stomach, but it quickly converts to pepsin once it encounters the acidic environment of the stomach.
Pepsinogen is secreted by the chief cells of the stomach. The stomach also secretes an enzyme called gastric lipase when lipids enter the stomach. Gastric lipase breaks down these lipids. Once food is broken down into smaller constituents, it can move into the small intestine, where other digestive enzymes, such as peptidases, sucrase, maltase, lactase and intestinal lipase, continue to break it down. The large intestine, however, does not produce digestive enzymes.