Genetically Engineered Insulin - Practice Questions & MCQ

• Management of adult-onset diabetes is possible by taking insulin at regular time intervals. 
• Insulin used for diabetes was earlier extracted from the pancreas of slaughtered cattle and pigs. 
• Insulin from an animal source, though caused some patients to develop an allergy or other types of reactions to the foreign protein. 
• Insulin is secreted by the Beta cells of the islets of Langerhans of the pancreas. 
• In 1921, Banting and Best succeeded in preparing a pure extract of insulin from the pancreatic islets of a dog with the help of Macleod. 
• Banting and Macleod won the 1923 Nobel Prize in Medicine or Physiology.

Structure of Insulin:

• Insulin consists of two short polypeptide chains: chain A and chain B, that are linked together by disulphide bridges.
• Chain A has 21 amino acids.
• Chain B has 30 amino acids.

Production of Insulin:

• In mammals, including humans, insulin is synthesised as a prohormone (like a pro-enzyme.
• The pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. 
• This C peptide is not present in the mature insulin and is removed during maturation into insulin. 
• The main challenge for the production of insulin using rDNA techniques was getting insulin assembled into a mature form.
• In 1983, Eli Lilly, an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. 
• Chains A and B were produced separately, extracted and combined by creating disulfide bonds to form human insulin.