What is the biosynthesis of insulin?

Updated: Jan 02, 2019
  • Author: Saranya Buppajarntham, MD; Chief Editor: Eric B Staros, MD  more...
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Insulin is a peptide hormone that is secreted from beta cells of the islets of Langerhans in the pancreas. It is initially synthesized in endoplasmic reticulum and Golgi apparatus as proinsulin; it is then cleaved to insulin and C-peptide. Although insulin and C-peptide are cosecreted in equal molar proportions, the ratio of serum insulin to C-peptide is 1:5-15. Fifty to sixty percent of insulin is extracted by the liver before it reaches systemic circulation, and it has a half-life of only 4 minutes. In contrast, C-peptide and proinsulin are excreted via the kidney. [6]

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