Biotechnology and its Applications — BIOLOGY STD 12 Science — Question

→ Insulin is produced by beta cells of pancreas.
→ Insulin plays important role in a sugar or carbohydrate metabolism.
→ Due to lack of insulin diabetes mellitus occurs in humans.
→ Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs.
→ Insulin from an animal source, though caused some patients to develop allergy or other types of reactions to the foreign protein.

→ Insulin consists of two short polypeptide chains: chain A and chain B.
→ Polypeptide Chain A contains 21 amino acids and chain B contains 30 amino acids that are linked together by disulphide bridges.
→ In mammals, including humans, insulin is synthesised as a pro-hormone (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 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.