Diabetes has been a problem in society for a long time and for decades the peoples suffering from this disease had to depend on the insulin isolated from the pancreas of the slaughtered calves. The problem in using this insulin was that it was not exactly similar to that of human insulin and due to this reason it caused allergic reactions in large number of the population using it. As a solution to this problem, human insulin was prepared synthetically using the techniques of genetic engineering.
The human insulin consists of two chains of polypeptide, chain A with 21 amino acids residue and chain B with 30 amino acids residue and both the chains are joined together with disulfide bonds. These chains are synthesized in the β cells of the islets of Langerhans present in the pancreas. In order to synthesize the human insulin artificially, the genes responsible for synthesis of both the polypeptide chains were isolated from the pancreas of a human and was then replicated and inserted in E.coli. The transformed bacteria were then selected and cloned multiple times to form a colony.
The transformed colonies synthesized the chains of amino acids separately which were then joined artificially to form the disulfide bonds which rendered fully functional insulin. This insulin has all the properties of human insulin and does not cause any allergic reactions. It is also readily absorbed in the body when compared to the animal insulin.