Question

If peptidases digest proteins into amino acids, why don’t they auto-digest the cells where they are synthesized?

Answer 1

Proteolytic enzymes are a group of enzymes that breaks long-chain molecules of proteins into short fragments and eventually into their componenets like amino acids. Proteolytic enzymes are also called as protease, proteinase or peptidase enzymes. These enzymes are commonly present in bacteria, certain types of algae, some virus and plants and they are most abundantly seen in animals. There are two different types of proteolytic enzymes, which are classified according to the sites where they catalyze the cleavage of proteins. They are exopeptidase (targets the terminal ends of the protein) and endopeptidase (target sites within proteins). The best known proteolytic enzymes are those present in the digestive tract. In the stomach protein materials are initially attcaked by gastric endopeptidase called as pepsin and from the stomach, these protein molecules pass through small intestine awhere they are further attacked by pancreatic enzymes which are from precurssors (trypsinogen, chymotrypsinogen, proelastase and procarboxypeptidase) produced by acinar cells in pancreas. Trypsinogen is converted into trypsin, an endopeptidase by an enzyme entrokinase sectreted from the walls of the stomach, which in turn activates the other precurssors. When the pancreatic enzymes become activated in the intestine, they convert proteins into free amino acids, which are easily absorbed by the cells of the intestinal wall. The pancreas also produces a protein called pancreatic secretory trypsin inhibitor, which binds to trypsin and blocks the activity and thus it is thought that the pancreas protects itself from auto-digestion.