Which enzyme is responsible for breaking down proteins into amino acids, in addition to trypsin?

Pepsin is an enzyme that specifically catalyzes the breakdown of proteins into smaller peptides and ultimately into amino acids. It is produced in the stomach and begins the process of protein digestion in the acidic environment of the gastric juice. Pepsin works effectively in the low pH of the stomach and is one of the first enzymes to initiate protein digestion before the partially digested proteins enter the small intestine, where other enzymes, like trypsin, continue this process. Thus, the significance of pepsin lies in its role in protein degradation, making the identification of this enzyme as a key player in protein digestion accurate.

Other choices do not function in this capacity: lipase is responsible for the digestion of fats, amylase breaks down carbohydrates, and bile salts aid in the emulsification of fats rather than protein digestion.