Question

Describe how human insulin is produced using the techniques of genetic engineering.

Hint:

Think of \textit{E. coli} as tiny factories making the A and B parts of insulin separately. These parts are then joined together chemically to make the final product.

Answer 1

The production of human insulin using genetic engineering revolutionized the treatment of diabetes, as it provided a source of insulin that was identical to human insulin, overcoming issues associated with animal-derived insulin. The process typically involves the following steps:
(A) Isolation of Human Insulin Genes: The genes encoding the A and B polypeptide chains of human insulin are identified and isolated. This can be done using reverse transcriptase to create cDNA from mRNA encoding these chains or by synthesizing the genes artificially.
(B) Insertion into Vectors: The isolated A and B chain genes are then inserted separately into expression vectors, which are typically plasmids (small, circular DNA molecules) that can replicate in host cells. These vectors contain regulatory sequences (like promoters) that allow for efficient transcription and translation of the inserted genes.
(C) Transformation into Host Cells: The recombinant plasmids containing the A and B chain genes are introduced into host cells, such as \textit{Escherichia coli} (\textit{E. coli}) bacteria. This process is called transformation.
(D) Culturing the Host Cells: The transformed \textit{E. coli} cells are cultured in large fermentation tanks under controlled conditions that promote their growth and the expression of the human insulin A and B chain genes. The bacteria act as miniature factories, producing the desired polypeptide chains.
(E) Production of Inclusion Bodies: The human insulin A and B chains are often produced as insoluble aggregates within the bacterial cells called inclusion bodies. This helps protect the proteins from degradation by bacterial enzymes.
(F) Extraction and Purification: The \textit{E. coli} cells are harvested and lysed (broken open) to release the inclusion bodies containing the A and B chains. These inclusion bodies are then separated and purified using various biochemical techniques.
(G) Chemical Joining of A and B Chains: The purified A and B polypeptide chains are then chemically treated to form the disulfide bonds that link them together in the correct configuration to produce functional human insulin. This step mimics the natural processing that occurs in human \(\beta\)-cells, although it is done in vitro.
(H) Final Purification and Formulation: The resulting human insulin is further purified to remove any contaminants and is then formulated into pharmaceutical preparations suitable for injection by diabetic patients. This genetic engineering approach allows for the large-scale production of pure and effective human insulin, which has been a life-saving therapy for millions of people with diabetes.