Humanproinsulin, the single-chain peptide precursor of insulin, consists of the insulin A and B chains connected by the 31 amino acid C-peptide. Cleavage of proinsulin by proteolytic enzymes produces insulin and free C-peptide.
Proinsulin C-peptide (human) is a 31-amino acid peptide that links the Proinsulin A and B chains, ensuring their proper folding, biological activity, and regulation of cellular functions.