Question

During the processing of the prohormone, proinsulin converted into the mature insulin by,

• A. B–peptide is removed from proinsulin.
• B. C–peptide is added to proinsulin.
• C. C–peptide is removed from proinsulin.
• D. A–peptide is removed.

Answer 1

Answer: (C)

Mature insulin consists of two polypeptide chains (51 amino acids), A and B consisting of 21 and 30 amino acids respectively. In mammals, insulin is synthesized from a preprohormone called preproinsulin. This inactive form has 110 amino acids with the signal peptide and C peptide. Proinsulin is formed by removal of the signal peptide and mature insulin is formed by removal of C peptide. This is followed by the formation of disulfide bonds between A and B chains leading to the formation of active insulin consisting of 51 amino acids.