Q.State the role of pancreatic juice in digestion of proteins.

Pancreatic juice, secreted by the exocrine acini of the pancreas into the duodenum through the pancreatic duct, carries three proteolytic enzymes, all released in inactive zymogen form so that the pancreas itself is not digested:

• Trypsinogen → trypsin: activated by enterokinase, an enzyme secreted by the intestinal mucosa (not by HCl). Trypsin is an endopeptidase — it cleaves internal peptide bonds of proteins, proteoses and peptones, producing shorter peptides. It also activates the other two pancreatic zymogens.
• Chymotrypsinogen → chymotrypsin: activated by trypsin. Like trypsin, it is an endopeptidase that breaks proteins/peptones down into smaller peptides; it additionally causes coagulation (clotting) of the milk protein casein.
• Procarboxypeptidase → carboxypeptidase: also activated by trypsin. Unlike the two enzymes above, carboxypeptidase is an exopeptidase — it removes one amino acid at a time from the free carboxyl (–COOH) end of peptide chains. …

List the three pancreatic proteolytic zymogens, name their activators (enterokinase for trypsinogen; trypsin for the other two), and state the specific action of each …

• Saying HCl activates trypsinogen — HCl only activates pepsinogen in the stomach; trypsinogen needs enterokinase. …