Figure 2.

Biosynthetic process from preprocalcitonin to mature calcitonin. Within ProCT, CT exists in a nonaminated, immature 33-amino acid form, terminated with a glycine. ProCT’s posttranslational processing results in production of several additional free peptides, as well as immature CT. Further modifications of immature forms of CT end up in a protein molecule with aminated C-terminus and a disulfide bridge between its various chains. Much of the bioactivity of the mature hormone may be linked to the amination of its carboxyl end.