Genetically engineered insulin
• Insulin contains two short polypeptide chains—chain A and chain B linked by disulphide bridges.
• In mammals, insulin is synthesised as a pro-hormone (that needs to be processed to become mature and functional hormone). It contains an extra stretch called C peptide.
• C peptide is absent in mature insulin and is removed during maturation into insulin.
• Earlier, insulin was extracted from pancreas of slaughtered cattle and pigs but some patients began developing allergies.
• Production of insulin by rDNA techniques was achieved by an American company, Eli Lilly, in 1983. It prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of E. coli for production. The A and B chains produced, were separated, extracted and combined, by creating disulfide bonds to form human insulin.
