CBSE · Class 12 · Biology · Biotechnology and its ApplicationsExplain the process of creating genetically engineered insulin (Humulin). Discuss the challenges faced initially and how Eli Lilly successfully produced recombinant insulin using E. coli.

Introduction to Insulin and Diabetes\nInsulin is a vital peptide hormone produced by the pancreas that regulates blood glucose levels. Patients suffering from Type-I diabetes mellitus require regular injections of insulin. Historically, insulin used for treating diabetic patients was extracted from the pancreas of slaughtered cattle and pigs. However, this animal-derived insulin caused allergic reactions, immune responses, and other complications in some patients due to minor structural differences from human insulin. Moreover, the availability of animal pancreas was limited compared to the growing demand.

Challenges in Recombinant Insulin Production\nInsulin consists of two short polypeptide chains—Chain A and Chain B—linked together by disulfide bonds. In humans, insulin is synthesized as a pro-hormone, which contains an extra stretch called the C-peptide. This C-peptide is removed during maturation to form mature functional insulin. The major challenge for scientists was that eukaryotic genes containing introns could not be directly expressed in prokaryotes like E. coli, and the synthesis of the two chains separately and joining them chemically posed massive procedural hurdles.

Eli Lilly and Company's Approach (1983)\nIn 1983, an American pharmaceutical company named Eli Lilly prepared two DNA sequences corresponding to A and B chains of human insulin.

• Plasmid Insertion: They introduced these DNA sequences into plasmids of Escherichia coli (E. coli) to produce insulin chains separately.
• Chain Synthesis: Chain A and Chain B were produced separately as fusion proteins linked to a bacterial protein.
• Extraction and Linking: The chains were extracted from E. coli cultures, separated from the bacterial protein, and combined by establishing hydrogen and disulfide bonds.
• Commercialization: This resulted in the successful creation of synthetic human insulin, commercially known as Humulin, which became the first recombinant DNA-derived pharmaceutical approved for human use.

Significance\nHumulin is identical to natural human insulin, minimizing adverse immune reactions and allergic responses. It ensures a virtually unlimited supply of pure insulin for the worldwide diabetic population, revolutionizing modern endocrinology and biotechnology.