Which substance is involved in the chemical digestion of protein?

Answer 1

Protein digestion occurs in the stomach and the duodenum through the action of three main enzymes: pepsin, secreted by the stomach, and trypsin and chymotrypsin, secreted by the pancreas. These enzymes break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids.

The proteolytic enzymes are all secreted in an inactive form, to prevent auto-digestion, and are activated in the lumen of the gut. Activation is caused by HCl in the case of the stomach enzyme pepsinogen, and by enteropeptidase and trypsin in the case of the pancreatic enzymes. Trypsin is secreted by the pancreas in the form of trypsinogen, which is activated in the duodenum by enterokinase to form trypsin. Trypsin then cleaves proteins into smaller polypeptides.