Enzymes are necessary for breaking down macronutrients into smaller forms that can be absorbed into the body: an essential part of gastrointestinal (GI) function. The enzyme pepsin is produced in the upper GI tract and acts as a proteolytic enzyme. It breaks down amino acid chains in proteins, even at a low pH. 1 Supplemental pepsin has been used to provide enzymatic support in patients with insufficient enzyme production.1