Which Statement About Insulin Is Not True

Which statement about insulin is not true?

A) It is synthesized as a precursor.
B) It probably exists in a tightly folded conformation at physiological concentrations in plasma.
C) It is composed of two peptide chains linked by disulfide bonds. When separated, these two chains will readily recombine to form active insulin in high yield.
D) It promotes glucose and amino acid uptake by muscle.
E) It is stored in the secretory granules of the beta cell of pancreatic islets as Zn-insulin along with an equimolar amount of C-peptide.