[Skip to Content]
[Skip to Content Landing]
December 1980

Insulin Biosynthesis and C-peptidePractical Applications From Basic Research

Am J Dis Child. 1980;134(12):1119-1121. doi:10.1001/archpedi.1980.02130240003001

The insulin molecule released into the circulation by the β cells of Langerhans' islets consists of two separate, straight polypeptide chains linked by disulfide bridges between and within the chains (Figure).1,2 These two chains are not separately manufactured; instead, the parent molecule synthesized on the ribosome consists of a larger precursor, proinsulin, a single coiled chain in which the amide terminus of the A-chain is linked to the carboxyl terminus of the B-chain by a connecting or C-peptide (Figure).1,2 Actually, an even larger precursor, pre-proinsulin, containing an additional peptide chain on the amino terminus of the A-chain is initially synthesized. This additional piece acts in a manner analogous to the leader in a film reel and is rapidly excised during synthesis.1,2 Further processing of proinsulin cleaves the C-peptide consisting of 31 amino acids from the insulin molecule at the sites indicated in the figure. As might be

First Page Preview View Large
First page PDF preview
First page PDF preview