THE LIFE-SAVING INDUSTRIAL PRODUCTION OFINSULIN

The use of genetic engineering in the treatment of diabetesmellitus

INTRODUCTIONInsulin was the first protein to be producedat a commercial level by thebiotechnological industry.In 1952, Fred Sanger published thecomplete sequence of the two chains thatcompose insulin protein.By 1971 Dorothy Hodgkin determinedthe three-dimensional structure of insulin,while she was working in the field of X-raycrystallography. This is how it became thefirst important protein to have its structure solved. The following year, Herbert W. Boyer andStanley Cohen collaborated to develop the recombinant DNA technology for therapeutic proteins.This method made it possible to insert a human gene into the genetic material of a commonbacterium, using restriction enzymes and DNA ligase. This “recombinant” micro-organism could nowproduce the protein encoded by the human gene. And even then, it was not until 1979 that humaninsulin could be produced in large quantities in the laboratories, using industrial fermentation tanks,with recombinant DNA.[2][1][3][5]

TOWARDS THE INDUSTRIALPRODUCTION OF INSULIN

Ever since Frederick Banting and Charles Best (twoscientists from Toronto) isolated a protein - called"isletin" from the pancreatic Islets of Langerhans - andinjected it into diabetic dogs, insulin has been used asa therapy for diabetes. Initially, insulin was extractedand purified from either porcine or bovine pancreases,but it was difficult to obtain large amounts of pureproduct: every year the Eli Lilly company used 56million pigs and cattle to address the USA marketdemand. Therefore, though the animal insulin ischemically similar to the human insulin (only one tothree amino acid differences), yet it is not identical andsome patients experienced significant immuneresponses. This was due to the fact that the immunesystem may recognize the animal insulin molecules as

non-self, thus neutralizing them, and making the insulin therapy ineffective.By early 1970s, in the United States, UCSF, Harvard and the Genentech company competed in orderto find the most effective method to synthesize human insulin to cure diabetic patients. DavidGoeddel’s (and his colleagues of Genentech) approach consisted in cloning and expressing the two

chains of insulin separately, then recombining them after cell division in fermentation tanks. Theiractive recombinant human insulin was a success and in 1982 FDA approved their approach. [1][5]

THE FUNCTION OF INSULIN in controlling glucose blood concentration & thetwo main TYPES OF DIABETES

THE RECOMBINANT DNA TECHNOLOGYThe recombinant human insulin can be synthesized in Escherichia coli cells, and it will not causeimmunological reactions.The structure of insulin protein hormone consists of two chains: an A chain composed of 21 aminoacids and a B chain composed of 30 amino acids. Both of these chains are linked via disulfidelinkages, and connected by an inactive C chain. [4][5][6]

1. The A and B insulin genes areextracted from human cells, andisolated plasmid DNA is cut withrestriction enzymes

2. The two genes are inserted intotwo different plasmids by DNAligase

3. The recombinant plasmids arereintroduced into Escherichia colibacteria, where the insulin geneswill be replicated.

4. Bacteria are placed intofermentation tanks, where theyfind the optimum conditions togrow and divide themselves.

5. Engineered bacteria multiplyproducing insulin, which isidentical to the human one.

6. Insulin is chemically removed fromthe beta-galactosidase protein(which provides stability to theprecursor A and B chains).

7. The A and B chains are combinedto produce functional insulin.This human insulin is purified andcan then be used to treat manypeople with diabetes withoutworrying about any allergicreaction. [4][5][6]

REFERENCES:1 Insulin: A pacesetter for the shape of modern biomedical science and the Nobel Prize, Flier J.S. andKahn C.R., Molecular Metabolism, 3 March 20212 https://science.sciencemag.org/content/219/4585/632.abstract3 https://www.nlm.nih.gov/exhibition/fromdnatobeer/exhibition-interactive/recombinant-DNA/recombinant-dna-technology-alternative.html4 https://www.chegg.com/learn/chemistry/organic-chemistry/structure-of-insulin5https://www.embl.fr/training/scienceforschools/teacher_training/teachingbase/insulin_ital/insulin_ital_rdl.pdf6 https://www.atrainceu.com/content/4-regulation-blood-glucose

Written by Bianca Manzini and Joshua Poltock