Insulin is an endogenous hormone produced in the pancreas. Insulin causes sugar to be absorbed from the blood into the liver and muscles. This causes the blood sugar level to drop.
Insulin, also known as insulinum, insulin hormone or islet hormone, can be assigned to the class of proteohormones. All members of this hormone class are characterized by a high fat solubility. In aqueous solutions, on the other hand, they remain virtually unaffected.
For all vertebrates and mammals, insulin is one of the vital hormones that must be substituted if there is a deficiency. Insulin is one of the most important drugs in diabetes. Insulin is usually used in type 1 diabetes and in advanced stages of type 2 diabetes that no longer respond to oral medication.
Insulin formation (synthesis)
The tissue hormone insulin is produced in so-called ß-cells of the islets of Langerhans in the pancreas. The genetic information concerning insulin synthesis is encoded in the short arm of the 11th chromosome. During insulin synthesis, the hormone precursor preproinsulin is produced in a first step.
With a length of 110 amino acids, this precursor is much larger than the actual, active hormone. During a processing phase (adaptation phase), the insulin precursor is shortened and modified in two steps. First, the protein is folded by forming so-called disulfide bridges.
This is followed by hormone processing, during which the actual shortening of the preproinsulin takes place. The so-called signal sequences are first separated from the still too long hormone precursor (the second precursor is formed: proinsulin). These usually comprise about 24 amino acids.
In the hormone precursor, the signal sequences serve as signals for absorption into special cell compartments. It is therefore a kind of recognition feature of the hormone. Subsequently, another part of the tissue hormone, the C-peptide, has to be separated.
After the hormone modification, mature, active insulin remains. This ultimately consists of two peptide chains (A- and B-chain) that are connected via two disulfide bridges. A third disulfide bridge forms a contact between two amino acids of the A-chain. The finished insulin molecules are then packed into vesicles and stabilized by the addition of zinc ions.
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