anti-Insulin, pAb

Insulin is a peptide hormone, produced by beta cells in the pancreas. It is composed of 51 amino acids in two peptide chains (A and B) linked by two disulfide bonds. It is however first synthesized as a single polypeptide called preproinsulin in pancreatic beta-cells. Preproinsulin contains a 24-residue signal peptide which directs the nascent polypeptide chain to the rough endoplasmic reticulum (RER). The signal peptide is cleaved as the polypeptide is translocated into lumen of the RER, forming proinsulin. Insulin is produced and stored in the body as a hexamer (a unit of six insulin molecules), while the active form is the monomer. The hexamer is an inactive form with long-term stability, which serves as a way to keep the highly reactive insulin protected.