Trypsin is part of the digestive system and degrades proteins, making it an enzyme known as a protease. It is initially formed as a larger, inactive molecule in the pancreas and is transported to the small intestine, where it is activated to digest food molecules. This protease is also a regulator of many other digestive proteases. A lack of its production in the pancreas is a component of the disorder cystic fibrosis.
Food that is made up of proteins is partially broken down in the stomach by proteases, and the smaller pieces travel into the small intestine. Proteases are enzymes that speed up the breakdown of proteins. Amino acids are the building blocks of proteins, and they are linked together by peptide bonds. The end goal of the digestion of proteins is to degrade them to amino acids, which can be utilized in cellular metabolism.
Trypsin is originally synthesized in the pancreas in a form known as trypsinogen, a zymogen. This larger molecule is inactive until it is transported to the small intestine and acted upon by enteropeptidase, another type of protease. Once this step has taken place, trypsin can activate itself. In addition to degrading proteins in digestion, this substance activates a number of other zymogens. Because of its important role in activating so many other proteases, pancreatic juice contains an inhibitor that blocks its activity while it is in the pancreas.
Along with chymotrypsin and a number of other proteases, trypsin is in a class known as serine proteases. This class of proteases is comprised of endopeptidases. They cleave within a protein molecule, instead of nibbling away at the ends. Serine proteases have a key serine amino acid at their active site.
Chymotrypsin and trypsin are very similar to each other in structure and chemical composition. The main difference is in the substrates they prefer. Trypsin cleaves by the amino acids arginine and lysine, while chymotrypsin prefers tryptophan, tyrosine, and phenylalanine. They are both optimal in the neutral pH environment of the small intestine.
A lack of transport of trypsin, and other digestive enzymes from the pancreas, is one of the factors involved in cystic fibrosis. This causes obstructions in the intestines to build up, interfering with the absorption of nutrients. Newborn babies are usually tested for the presence of this enzyme in their blood, and a high level is typically indicative of cystic fibrosis. For older individuals, activity in stool can be measured. If the results are negative, further testing is merited.