Insulin
Insulin — A 51-amino acid peptide hormone consisting of two disulfide-linked chains, produced by pancreatic beta cells and central to glucose metabolism research.
What Is Insulin?
Insulin is a 51-amino acid peptide hormone consisting of two chains (A-chain: 21 residues, B-chain: 30 residues) connected by two interchain disulfide bonds plus one intrachain disulfide bond in the A-chain. Molecular weight: 5808 Da. Produced by pancreatic beta cells, insulin is the most important peptide in metabolic regulation and was the first protein to have its amino acid sequence determined (Frederick Sanger, 1951, Nobel Prize).
Mechanism of Action
Insulin binds the insulin receptor (IR), a receptor tyrosine kinase that autophosphorylates and activates insulin receptor substrate (IRS) proteins. This triggers two main cascades: PI3K/Akt (metabolic effects: glucose uptake via GLUT4 translocation, glycogen synthesis, lipogenesis) and Ras/MAPK (growth effects: cell proliferation and gene expression). The IR also crosstalks with the IGF-1 receptor.
Historical Significance
- First sequenced protein: Sanger determined the complete amino acid sequence (1951, Nobel Prize 1958)
- First synthesized protein: Total chemical synthesis achieved independently by three groups in 1963-1965
- First recombinant protein drug: Humulin (recombinant human insulin) approved by FDA in 1982
- Structural biology milestone: First protein structure solved by X-ray crystallography (Dorothy Hodgkin, 1969)
Handling
Insulin requires careful handling due to its three disulfide bonds and aggregation propensity. Store lyophilized at -20°C. Reconstitute in dilute HCl (pH 2-3) for stock solutions. Insulin forms amyloid fibrils at high concentrations, elevated temperatures, or acidic pH with agitation.
Frequently Asked Questions
What is Insulin?
A 51-amino acid peptide hormone consisting of two disulfide-linked chains, produced by pancreatic beta cells and central to glucose metabolism research.
Why is Insulin important in peptide research?
Insulin is a fundamental concept in compound as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.