On the role of the proinsulin C-peptide

Intracellular cleavage of protein and polypeptide precursors is now recognized as a widely occurring biosynthetic mechanism. As this field has developed, proinsulin and its cleavage patterns and secretory products have served as useful models for investigations of other systems. A particularly relevant aspect of the proprotein concept is the simple mechanism it provides for the coördinate synthesis and discharge of related peptides from endocrine or other secretory cells. This report reviews briefly the role of the proinsulin C-peptide, first in terms of its special biosynthetic functions, which are unique to the assembly of the two-chain insulin structure, and then with regard to its more general implications for other biosynthetic and secretory systems.