Insulin used for diabetes was earlier exlier extracted from pancreas of slaughtered cattle and pigs. Insulin consists of two short polypeptide chains A and chain B that are linked together by disulphide bridges . In mammals including humans , insulin is synthesised as aprohormone (like a pro - enzyme the pro - hormone ) also need to be processed before it becomes a fully mature and functional hormone.
In America , a 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.
