Insulin is a tiny protein consisting of two linked polypeptide chains derived from a single proinsulin chain. The two chains, "A" consisting of 21 amino acids and "B" of 30 amino acids, are linked by two disulfide bridges. Insulin was the first protein to have its amino acid sequence determined (in 1955).
Underproduction of insulin results in the accumulation of large amounts of glucose in the blood and its subsequent excretion in the urine. This condition, known as diabetes mellitus, can be treated successfully by insulin injection. If insufficient insulin is taken, diabetic coma may result, while in excess hypoglycemia supervenes; both require prompt medical treatment.
The isolation of insulin as a pancreatic extract by F. G. Banting and C. H. Best in 1921 was a milestone in medical and scientific history. Insulin in medicine used to be extracted from animals. Today, it can be produced artificially by inserting the genes of human insulin into bacteria which multiply in fermentation plants.
Related category• BIOCHEMISTRY
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