<P> The post translational modification of proinsulin to mature insulin only occurs in the beta cells of the islets of Langerhans . When proinsulin is transported through the Golgi apparatus the C - peptide is cleaved . This cleavage occurs with the aid of two endoproteases . Type I endoproteases , PC1 and PC3 , disrupt the C peptide - B chain connection . PC2 , a type II endoprotease , cleaves the C peptide - A chain bond . The resulting molecule , now mature insulin , is stored as a hexamer in secretory vesicles and is stabilized with Z n 2 + ( \ displaystyle Zn ^ ( 2 + ) ) molecules until it is secreted . </P>
mention the chemical change that proinsulin undergo to be able to act as mature insulin
post translational modification