`kəgŏn), hormone hormone, secretory substance carried from one gland or organ of the body via the bloodstream to more or less specific tissues, where it exerts some influence upon the metabolism of the target tissue...... Click the link for more information. secreted by the α cells of the islets of Langerhans, specific groups of cells in the pancreas pancreas (păn`krēəs), glandular organ that secretes digestive enzymes and hormones.
..... Click the link for more information. . It tends to counteract the action of insulin insulin, hormone secreted by the β cells of the islets of Langerhans, specific groups of cells in the pancreas . Insufficiency of insulin in the body results in diabetes . Insulin was one of the first products to be manufactured using genetic engineering .
..... Click the link for more information. , i.e., it raises the concentration of glucose in the blood. Glucagon was first purified and crystallized in 1955; the amino acid sequence of this 29-amino acid polypeptide (see peptide peptide, organic compound composed of amino acids linked together chemically by peptide bonds. The peptide bond always involves a single covalent link between the α-carboxyl (oxygen-bearing carbon) of one amino acid and the amino nitrogen of a second amino acid.
..... Click the link for more information. ) was published in 1956–57. One of the most important actions of glucagon is the promotion of glycogenolysis, i.e., the degradation of glycogen glycogen (glī`kəjən)
..... Click the link for more information. to glucose, in the liver. Glucagon stimulates adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate adenosine triphosphate (ATP) (ədĕn`əsēn trī'fŏs`fāt)
..... Click the link for more information. to 3′5′-cyclic adenosine monophosphate adenosine monophosphate (AMP) (ədĕn`əsēn mŏn'əfŏs`fāt)
..... Click the link for more information. (cyclic AMP).
glucagon [′glü·kə‚gän]
Glucagon
The protein hormone secreted by the pancreas which is known to influence a wide variety of metabolic reactions. Glucagon, along with insulin and other hormones, plays a role in the complex and dynamic process of maintaining adequate supplies of sugar in the blood. Glucagon has often been called the hyperglycemic-glycogenolytic factor because it causes the breakdown of liver glycogen to sugar (a process known as glycogenolysis) and thereby increases the concentration of sugar in the bloodstream (a condition known as hyperglycemia). Glucagon may also be involved in the regulation of protein and fat metabolism, gastric acid secretion and gut motility, excretion of electrolytes (such as sodium, potassium and chloride) by the kidney, contractility of heart muscle, and release of insulin from the pancreas. Glucagon is used in human medicine chiefly in certain diabetic conditions when a dangerously low blood sugar must be rapidly raised. See Carbohydrate metabolism, Glycogen, Hormone, Insulin, Pancreas
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