Pepsin functions best in what part of the digestive system?

Pepsin is an enzyme that is produced by the chief cells of the stomach and is active in the stomach. It functions best in the acidic environment of the stomach, which has a pH of around 1.5 to 2.0. Pepsin breaks down proteins into smaller peptides and is particularly effective in digesting collagen, a protein found in connective tissue. The hydrochloric acid produced by the parietal cells of the stomach helps to create the acidic environment necessary for pepsin to work effectively. Pepsin is inactive at higher pH levels, such as those found in the small intestine, and its activity is therefore limited to the stomach.