Insulin (Latin insula, "island", as it is produced in the Islets of Langerhans in the pancreas) is a polypeptide hormone that regulates carbohydrate metabolism. Apart from being the primary effector in carbohydrate homeostasis, it also has a substantial effect on small vessel muscle tone, controls storage and release of fat (triglycerides) and cellular uptake of both amino acids and some electrolytes. In this last sense, it has anabolic properties. Its concentration (more or less, presence or absence) has extremely widespread effects throughout the body.

Insulin is used medically in some forms of diabetes mellitus. Patients with Type 1 diabetes mellitus depend on exogenous insulin (injected subcutaneously) for their survival because of an absolute deficiency of the hormone; patients with Type 2 diabetes mellitus have either relatively low insulin production or insulin resistance or both, and a non-trivial fraction of Type 2 diabetics eventually require insulin administration when other medications become inadequate in controlling blood glucose levels. Insulin structure varies slightly between species. Its carbohydrate metabolism regulatory function strength in humans also varies. Pig insulin is particularly close to the human one.

The exact sequence of amino acids comprising the insulin molecule, the so-called primary structure, was determined by British molecular biologist Frederick Sanger. It was the first protein the structure of which was completely determined. For this he was awarded the Nobel Prize in Chemistry in 1958. In 1967, after decades of work, Dorothy Crowfoot Hodgkin determined the spatial conformation of the molecule, by means of X-ray diffraction studies. She also was awarded a Nobel Prize.

Formal Chemical Name (IUPAC)

References

http://en.wikipedia.org/wiki/Insulin

http://pdbbeta.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb14_1.html