Trypsinogen is the inactive form or precursor of trypsin. Trypsin is a proteolytic enzyme, it is secreted by the pancreas as trypsinogen. Trypsinogen is converted to trypsin by enterokinase, which is an enzyme secreted by the intestinal mucosa.
Function and Activation
Trypsinogen is a proenzyme or zymogen of trypsin, a proteolytic enzyme secreted by the pancreas. Trypsin is required for protein digestion, it hydrolyses proteins. It acts on proteins and partially hydrolysed proteins reaching the intestine. It converts proteins, peptones and proteoses of the chyme to dipeptides.
Trypsin is stored in the pancreas as trypsinogen because in the active form it can damage the pancreatic tissues. Trypsin is released into the duodenum by the hepatopancreatic duct.
Trypsinogen is activated by the enterokinase enzyme in the intestine. Enterokinase is secreted by the intestinal mucosa. Enterokinase is secreted by the cells of the duodenum.
Trypsin is a serine protease. It mostly hydrolyses peptide bonds at the carboxyl side of the amino acids lysine and arginine.
Enterokinase cleaves the peptide bond in trypsinogen after 15th amino acids at lysine residue. The N-terminal residues are discarded and the 16th amino acid now becomes the new N-terminal residue. The further rearrangement of the protein converts it to the active trypsin enzyme. Since trypsin also cleaves peptide bonds after lysine/arginine residue, it breaks other trypsinogens and acts as an autocatalyst.
Trypsin activates other enzymes of pancreatic juice. It also stimulates cleavage of trypsinogen to trypsin, i.e. autoactivation.
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