Proinsulin
Proinsulin is a prohormone and the precursor of the peptide hormone insulin . Insulin is produced as preproinsulin in the β-cells of the islets of Langerhans in the pancreas (pancreas). This consists of the signal peptide (24 AA ), the B chain (30 AA), the C peptide (31 AA) and the A chain (21 AA). The signal peptide is split off when the preproinsulin is secreted into the cisterns of the endoplasmic reticulum (ER). What remains is the proinsulin consisting of the B chain, the C peptide and the A chain. The proinsulin can fold in the ER . It is absorbed and stored in the Golgi apparatus . If necessary, the C-peptide is split off by membrane-based proteases . The prohormone proinsulin is converted into the active hormone insulin, which consists of two polypeptide chains that are covalently linked by two intermolecular disulfide bridges . The insulin is released from the vesicles into the blood by exocytosis .
Proinsulin (normal value in humans: below 11 pmol / l) has the following effects:
- Increase in contra-insulin (anti-insulin) hormones
- Release of angiotensinogen (with increased blood pressure)
- Release of fatty acids (with the following lipid metabolism disorder )
- Release of proinflammatory (inflammation-promoting) processes mediating substances such as interleukin-6 and TNF-alpha (with macrophage activation and progression of arteriosclerosis )
See also
swell
- ↑ UniProt P01308
- ↑ Richard Daikeler, idols Use, Sylke Waibel: diabetes. Evidence-based diagnosis and therapy. 10th edition. Kitteltaschenbuch, Sinsheim 2015, ISBN 978-3-00-050903-2 , p. 17 f.