Proinsulin

Proinsulin is a prohormone and the precursor of the peptide hormone, insulin. Insulin is formed as a preproinsulin in the β - cells of the islets of Langerhans of the pancreas (pancreatitis ). It consists of the signal peptide (24 AA), the B chain (30 AS), the C- peptide (31 AS) and the A chain (21 AS). The signal peptide is cleaved (ER) in the cisterns of the endoplasmic reticulum for secretion of preproinsulin. Left proinsulin is composed 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 cleavage of the C- peptide by membrane proteases occurs. For example, the proinsulin prohormone is transferred to the active insulin hormone, consisting of two polypeptide chains that are covalently linked to one another via two intermolecular disulfide bonds. The insulin is released from the vesicles by exocytosis into the blood.

Swell

• Diabetology
• Precursor protein