Trypsinogen

Definition – What is trypsinogen?

Trypsinogen is the inactive precursor, a so-called proenzyme, of an enzyme that is produced in the pancreas. Together with the remaining pancreatic secretion, known as pancreatic saliva, the proenzyme trypsinogen is released via the pancreatic ducts into the duodenum, a part of the small intestine. This is where activation to the enzyme trypsin takes place. This enzyme is categorized as a “hydrolase”, i.e. it is capable of splitting connections between individual amino acids. This process takes place in the small intestine, whereby the proteins that are ingested with food are split into smaller fragments of amino acids, which allows them to be absorbed into the body.

How does the activation to Trypsin work?

The activation from trypsinogen to trypsin can be done in two different ways. In both ways, activation does not occur in the pancreas or its ducts, but only in the duodenum, a part of the small intestine.

• For the one option in the activation to trypsin, another enzyme is needed.

  This enzyme is produced in the brush border, i.e. the superficial cells, of the duodenum. It is called enteropeptidase or enterokinase. The enzyme is categorized under hydrolases.

  This means that they can reversibly cleave the compounds of individual amino acids, which give the proenzyme trypsinogen its structure, by consuming water molecules. During the activation of trypsinogen to trypsin, a chain of six amino acids, a so-called hexapeptide, is split off from the proenzyme trypsinogen by consuming water. This results in a shortened amino acid chain compared to previously.

  The process is called limited proteolysis. However, the enzyme is now present in its active form and can split further amino acid chains in order to break down and digest proteins in the following.

• The second variant of activating trypsinogen to trypsin is represented by the already active enzyme trypsin. Trypsin can not only split foreign proteins into smaller amino acid chains, but can also shorten the body’s own pro-enzymes such as trypsinogen by several amino acids.

  Trypsin particularly likes to split after the sixth amino acid of trypsinogen. This means that a hexapeptide is cleaved off, which converts the trypsinogen into its active form, trypsin. Besides trypsinogen, active trypsin can convert three other enzymes that are important for digestion into their active form.

  There are also two factors that are important for activation, which are not obvious at first. On the one hand, the effect of trypsin is particularly good at a slightly basic pH value of 7 to 8, which activates more trypsinogen. On the other hand, trypsinogen is released in the pancreas with a trypsin inhibitor. This inhibitor prevents premature activation within the pancreas and is only broken down in the duodenum.