Mention the main challenge for the production of genetically engineered human insulin. Explain how it was produced by Eli Lilly, an American company.

The main challenge for the production of genetically engineered human insulin was the assemblage of the insulin into its mature form by the removal of the C peptide chain.

Production of human insulin by Eli Lilly-

i. Artificially prepared two DNA sequences corresponding to the two chains A and B of human insulin. It was then introduced into a plasmid of E.coli to produce the insulin chains. Thus, chains A and B were produced separately. But, these were associated with β- galactosidase. They were treated with cyanogen bromide to remove β- galactosidase and obtain pure A and B chains. These were then combined by creating disulfide bonds between them to form human insulin.