Calibrated to the WHO 1st International Standard 1975 (66/304), Arbor Assays Insulin EIA measures insulin with a sensitivity of 48.8 pg/mL.
The human insulin protein is a 51 amino acid anabolic peptide-hormone that is secreted by pancreatic ß-cells in the Islets of Langerhans. Insulin consists of two chains (A and B) connected by disulfide bonds (1). Its primary functions are the stimulation of glucose uptake from the systemic circulation, as well as the suppression of hepatic gluconeogenesis, thereby serving a major role in glucose homeostasis and preventing the metabolic disorder diabetes mellitus. The work of Banting, Best, Collip and MacCleod in the early 1920’s resulted in the identification of a substance in extracts of pancreas that had the remarkable ability to reduce blood glucose levels in diabetic animals (2) and by 1923 these pancreatic extracts were being used to successfully treat diabetic patients. Insulin exists primarily as a monomer at low concentrations (~10-6 M) and forms dimers at higher concentrations at neutral pH (3). At high concentrations and in the presence of zinc ions, insulin aggregates further to form hexameric complexes (4). Preproinsulin, the first translational product from the insulin gene, is a 110 amino acid polypeptide with a 24 amino acid signal peptide.
The major function of insulin is to counter the concerted actions of a number of hyperglycemia-generating hormones and to maintain low blood glucose levels. In addition to its role in regulating glucose metabolism, insulin stimulates lipogenesis, diminishes lipolysis, and increases amino acid transport into cells. Because there are numerous hyperglycemic hormones, untreated disorders associated with insulin generally lead to severe hyperglycemia and shortened life span. Insulin also exerts activities typically associated with growth factors. Insulin is a member of a family of structurally and functionally similar molecules that include the insulin-like growth factors and relaxin. The tertiary structure of all four molecules is similar, and all have growth-promoting activities. Insulin modulates transcription and stimulates protein translocation, cell growth, DNA synthesis, and cell replication; effects that it holds in common with the insulin-like growth factors and relaxin (see reviews: 5,6).
Insulin Hexameric Structure
The NEW Insulin EIA Kit, K046-H1, from Arbor Assays allows for simple, sensitive, rapid determination of insulin in serum, plasma or culture media. Calibrated to the WHO 1st International Standard 1975 (66/304) it measures insulin with a sensitivity of 48.8 pg/mL. It also detects bovine and porcine insulin and likely other mammalian insulins. It does NOT measure rodent insulin. Everything is stable at 4°C and is supplied liquid.
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1. Sanger, F., (1959) “The Chemistry of Insulin” Science, 129:1340-1344.
2. Bliss, M., (1982) “The Discover of Insulin” University of Chicago Press, Chicago.
3. Frank, BH., Pekar, AH., & Veros, AJ. (1972) “Insulin and proinsulin conformation in solution” Diabetes [Suppl. 2] 21:486-4914.
4. Blundell, T, Dodson, G, Hodgkin, D, Mercola, D., (1972) “Insulin: the structure in the crystal and its reflection in chemistry and biology.” Adv. Protein Chem. 26:279-402.
5. Nishi M, and Nanjo K., (2011) “Insulin gene mutations and diabetes.” J. Diab. Invest. 2:92-99.
6. Taniguchi, CM, Emanuelli, B and Kahn CR, (2006) “Critical nodes in signalling pathways: insights into insulin action” Mol. Cell. Biol. 7:85-96.