Final answer:
Pepsin is a digestive enzyme that metabolizes proteins and is secreted by the stomach. Trypsin and chymotrypsin also play a role in protein digestion and are secreted by the pancreas.
Step-by-step explanation:
A digestive enzyme that metabolizes proteins is pepsin. This enzyme is secreted by the stomach's chief cells. Pepsin works in the highly acidic environment of the stomach to break down protein structures into smaller peptides. It's crucial for the initial stages of protein digestion before the partially digested proteins move on to the small intestine for further processing.
Another set of protein-digesting enzymes include trypsin and chymotrypsin, which are secreted by the pancreas. These enzymes specifically target proteins after they have left the stomach and entered the small intestine. They further break down the resulting peptides into even smaller fragments that can eventually be absorbed as amino acids by the body.