- The Wonderful Hormone - INSULIN By Jeremy Wynn Cell Physiology

Insulin What is Insulin –Where does it come from? –What is the big deal about it? –What is the actual structure? Problems with Insulin –What are the classifications of diabetes? –What is done about it?

What the big deal about Insulin?? Insulin is a naturally occurring hormone, produced in the Islets of Langerhans of the pancreas, that regulates the metabolism of carbohydrates, fats, and starches in the body. Insulin is required by the cells of the body in order for them to remove and use glucose from the blood. Insulin stimulates the formation of glycogen in the muscles and in the liver. Insulin also controls the uptake of valine, leucine, and isoleucine by the muscles, which in turn helps to increase the synthesis of muscle proteins.

The Actual Structure Structure –A single insulin molecule consists of 2 polypeptide chains, A (21 amino acids) and B (30 amino acids) –The chains being held together by two disulfide bonds. A third disulfide bond is present within the A chain.

- Structure of Human Insulin -

Other Important Facts about the Structure Insulin molecules have a tendency to form dimers in solution due to hydrogen- bonding between the C-termini of B chains. Additionally, in the presence of zinc ions, insulin dimers associate into hexamers.

The Insulin Dimer and Hexamer

What to do about the formation of Dimers and Hexamers? The Lys and Pro are reversed. –This minimizes the tendency to form dimers and hexamers

Problems associated with Insulin Type I AND II Diabetes Mellitus –Type I, which is genetic, is caused by an autoimmune response of the white blood cells to destroy the beta cells of the pancreas Take insulin injections –Type II which is more common is usually caused by too high an insulin concentration in the blood stream. This is caused by the target cells' hyporesponsiveness to insulin. Placed on an exercise program

Clinical Production of Insulin Insulin was first synthesized in 1979 in E. coli cells through the use of recombinant DNA techniques. In 1982, synthesized insulin produced by genetically altered bacteria was approved for use with insulin dependent patient –This form of insulin is an exact match to that which is made in the body

Summary Insulin is a hormone produced by the pancreas that regulates blood glucose levels and –stimulates glucose transport –stimulates amino acid transport –Increases glycogen synthase activity –increases the rate of general protein synthesis Insulin consists of an A chain that has 21 a.a. and a B chain that has 30 a.a. –With 3 disulfide bonds Diabetes Mellitus –Type I – Low level, genetic, autoimmune disease –Type II – High levels, target cells not responding, increase adipose tissue Insulin can be manufactured by –Pig Insulin –Insulin made by E. Coli by recombinant DNA techniques