Although insulin was recognized to be a protein shortly after its discovery, the elucidation of its primary structure came many years alter with the development by Sanger and coworkers of methods to determine primary sequence of protein.
The primary structure of a protein is its amino acid sequence. It is a protein with an isoelectric point of 5.3. Its molecular weight depends on the degree of aggregation of the basic sub-unit of molecular weight 5734.
Known insulins are composed of two polypeptide chains that are linked to one another by disulfide bonds.
It is synthesized as a pro-hormone, pre-pro-insulin, which is split to yield pro-insulin. Pro-insulin is proteolytically split further into insulin and the connecting peptide (C-peptide); both are secreted from the beta-cells in equimolar amounts.
Though relatively stable to heat, organic solvents and low pH, insulin is extremely vulnerable to digestive enzymes like pepsin and chymotrypsin.
Chemical properties of insulin
