Biotechnology and its Applications — BIOLOGY STD 12 Science — Question

Insulin used for diabetes was earlier extracted from pancreas of slaughtered cattle and pigs, Insulin consists of two short polypeptide chains; chain A and chain B that are linked together by disulphide bridge.

In mammals, including humans, insulin is synthesised as a prohormone (like a pro- enzyme, the pro-hormones also needs to processed before it becomes a fully mature and functional hormone) which contain 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 r-DNA techniques was getting insulin assembled into a mature into a mature form.

Fig: maturation of pro-insulin into insulin after removal of C-peptide (to be simplified)

1993 Eily Lilly an American company prepared two-DNA sequences corresponding to A and B, chain of human Insulin and Introduced them in plasmid of E. coli to produce Insulin chains, chain A and B were produced separately, extracted and combined by creating disulfide bonds to from human Insulin.