Insulin is the most important regulatory hormone in nutrient homeostasis. It was first isolated from pancreatic tissue in 1921 by Banting and Best. Appropriate target tissue responses to insulin added to insulin synthesis and secretion are necessary to maintain normal fuel balance (Lebovitz, 2001).
Biochemistry:
Figure: Human proinsulin and insulin biochemistry, Junqueira et al., 1986 Insulin is a protein consisting of 51 amino acids contained within two peptide chains. A chain with 21 amino acids and B chain with 30 amino acids with two disulfide bridges connected the A and B chains. Another disulfide bridge links positions 6 and 11 in the A chain. (DeMeytes,1994)
Insulin receptor:
For insulin to exert its biological effects, it must first bind to specific receptors on the cell surface of all insulin target tissues. The insulin receptor is a glycoprotein consisting of two α-subunits and two β-subunits linked by disulfide bonds. The α -subunit of the insulin receptor faces outwards and contains the insulin binding domain, whereas the β-subunit express insulin stimulated kinas activity directed towards its own tyrosine residues. The α -subunit is totally extracellular, whereas the β-subunit is a transmembrane protein (Caeatham & Khan, 1995). …show more content…
This binding causes autophosphorylation of certain tyrosine molecules which causes activation of several intracellular insulin receptor molecules such as insulin receptor substrates (IRS), phosphatidylinositol-3-kinase (PI-3k) and other mediating
Biochemistry:
Figure: Human proinsulin and insulin biochemistry, Junqueira et al., 1986 Insulin is a protein consisting of 51 amino acids contained within two peptide chains. A chain with 21 amino acids and B chain with 30 amino acids with two disulfide bridges connected the A and B chains. Another disulfide bridge links positions 6 and 11 in the A chain. (DeMeytes,1994)
Insulin receptor:
For insulin to exert its biological effects, it must first bind to specific receptors on the cell surface of all insulin target tissues. The insulin receptor is a glycoprotein consisting of two α-subunits and two β-subunits linked by disulfide bonds. The α -subunit of the insulin receptor faces outwards and contains the insulin binding domain, whereas the β-subunit express insulin stimulated kinas activity directed towards its own tyrosine residues. The α -subunit is totally extracellular, whereas the β-subunit is a transmembrane protein (Caeatham & Khan, 1995). …show more content…
This binding causes autophosphorylation of certain tyrosine molecules which causes activation of several intracellular insulin receptor molecules such as insulin receptor substrates (IRS), phosphatidylinositol-3-kinase (PI-3k) and other mediating