Protease enzymes break down proteins into peptides, while peptidase enzymes break down smaller pieces of proteins into amino acids. Pepsinogen is secreted by the gastric glands into the stomach, which is a highly acidic environment after a person eats.
The acidity causes the pepsinogen to activate, breaking down proteins as the enzyme pepsin. Other enzymes such as chymotripsin, trypsin and carboxypedtidase also aid in the digestion of proteins. Proteases and petidases are also used in some detergents to break down organic stains. Protease inhibitors are used to help patients with the AIDS virus, because the virus uses proteases as it reproduces.