Which enzyme is responsible for breaking down proteins into smaller polypeptides?

Pepsin is a digestive enzyme that is specifically designed to break down proteins into smaller polypeptides. It is secreted by the stomach in an inactive form called pepsinogen, which is then activated in the acidic environment of the stomach. Once activated, pepsin begins to cleave the long chains of amino acids that make up proteins, facilitating their digestion.

This action helps prepare proteins for further breakdown by other enzymes in the small intestine, where additional digestion occurs. While protease is a more general term that encompasses any enzyme that breaks down proteins, pepsin is a specific type of protease that operates optimally in the stomach's acidic conditions.

Amylase, in contrast, is an enzyme that digests carbohydrates, and lipase is involved in the digestion of fats. Their functions are distinct from the protein-digesting role of pepsin, highlighting the specialization of digestive enzymes in processing different macromolecules.