Description
Insulin and the IGFs are members of the insulin family of molecules. IGF-I and II are structurally homologous to proinsulin, and can be thought of as taking the shape of an exaggerated, inverted letter G. Intrachain disulfide bonds link sections of the G. The single chain insulin propeptide consists of a 30 amino acid B chain (aa 2554), a C-peptide (aa 5589), and a 21 aa A chain (aa 90110). Removal of the C-peptide by proteolysis enables the formation of mature Insulin, a disulfidelinked heterodimer of the A and B chains. Circulating C-peptide levels are elevated in hyperinsulinism, obesity, and type II diabetes