Insulin used to be extracted from cows and pigs. The process often resulted in extracts with impurities. Even with refined techniques, the extracted protein was not a human protein and sometimes caused immune reactions in people with diabetes.
In 1955, Frederick Sanger determined the amino acid sequence of human insulin. This sequence was used to genetically engineer bacteria to produce large amounts of pure human insulin. Insulin is one of the first examples of a drug produced using genetic engineering techniques to make safer, more efficient quantities. Now individuals with diabetes use genetically engineered insulin to control their disease without the side effects caused by cow or pig insulin.
