Chymotrypsin vs Trypsin

The entire digestive tract releases various enzymes to break down complex food molecules into simpler, more digestible ones. The stomach, liver, pancreas all elaborate juices to help convert our food into carbohydrates, proteins and fats so that our body can absorb and utilise them. The pancreas, situated in the abdomen, right below our stomach, is a leaf-shaped organ which releases the maximum number of digestive enzymes. Both trypsin and chymotrypsin, are digestive enzymes produced by it.

Now, since these enzymes are so strong that they are capable of digesting away even the pancreas itself, they are all released from the cells in inactivated forms. These are also called as precursors. The precursors need to be converted to the active form by another chemical substance or get activated at certain temperatures. Trypsin is released as trypsinogen from the pancreas while chymotrypsin is released as chymotrypsinogen. Trypsinogen is released along with another trypsin-inhibiting enzyme to prevent any accidentally activated trypsin from damaging the pancreas. Along with trypsinogen and chymotrypsinogen, procarboxypeptidase, many lipases, elastases and proteases are elaborated and emptied via the pancreatic duct into the small intestine (duodenum).

The release of these enzymes or zymogens from the pancreas is stimulated by a neurotransmitter called Cholecystokinin (CCK). CCK is released by the duodenum in response to fatty/protein-rich food in the lumen.

Trypsinogen gets converted into its active form trypsin when it comes into contact with the brush border of the small intestine. Here, an enzyme called enterokinase is released from the brush-border villi. Now, the activated trypsin goes on to activate all other released enzymes like the chymotrypsinogen, procarboxypeptidase, etc. into their active forms of chymotrypsin and carboxypeptidase, etc.

Trypsin and chymotrypsin are both protein digesting enzymes. They break down proteins into their component amino acids. Trypsin digests proteins by breaking basic amino acids like arginine and lysine while chymotrypsin breaks aromatic amino acids like tryptophan, phenylalanine and tyrosine. Chymotrypsin basically cleaves the peptide amide bonds in polypeptides. It also acts on leucine and methionine amino acids.

Chymotrypsin has 3 isomeric forms namely chymotrypsinogen B1, chymotrypsinogen B2 and chymotrypsin C. Similarly, trypsin has 3 isoenzymes called trypsin 1, trypsin 2 and mesotrypsin. The functions of these isomeric forms of both trypsin and chymotrypsin are the same.
Medically, trypsin is extremely important as intra-pancreatic activation of trypsin can cause a terrible cascade of reactions. It will activate all other digestive enzymes, the lipases, the proteases, the elastases and will start digesting the pancreas from within itself leading to acute pancreatitis. Acute pancreatitis is a life threatening condition if not identified early and treated adequately. On the other hand, a deficiency of trypsin can lead to another disorder called meconium ileus in a newborn. Due to deficiency of trypsin, the meconium (neonatal feces) is not liquefied and cannot pass through the intestines, producing a blockage and complete intestinal obstruction. This is a surgical condition and needs to be treated immediately.

Take home pointers:

Trypsin and chymotrypsin are both protein digesting enzymes released by the exocrine pancreas in the abdomen.
Both are released in their inactivated forms, trypsinogen and chymotrypsinogen.
Trypsinogen is activated by enterokinase which is released by the brush border cells of the duodenum.
Trypsin, in turn, activates chymotrypsin by converting it from chymotrypsinogen.
Trypsin activates other enzymes like protease, lipases, elastases and carboxypeptidases.
Trypsin is extremely potent and is released along with a trypsin-inhibiting enzyme within the pancreas.
Trypsin if activated within the pancreas can cause acute pancreatitis which is a life-threatening condition of autolysis of pancreatic tissue.
Deficiency of trypsin occurs in cystic fibrosis causing meconium ileus in neonates.

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