Question

$C-$ peptide of human insulin is

• A. A part of mature insulin molecule
• B. Responsible for formation of disulphide bridges
• C. Removed during maturation of proinsulin to insulin
• D. Responsible for its biological activity.

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 synthesised 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.
Thus, the correct option is option "C" , i.e., $C-$ peptide of human insulin is removed during maturation of proinsulin to insulin