What structural changes occur during the activation of insulin from proinsulin?

• A. Proinsulin is phosphorylated to become active insulin.
• B. Proteolytic cleavage removes a portion of proinsulin, resulting in two polypeptide chains linked by disulfide bonds.
• C. Proinsulin is methylated to become active insulin.
• D. Proinsulin is acetylated to become active insulin.

Answer: (B)