The number of disulphide linkages present in insulin are

Options

A. 3
B. 4
C. 1
D. 2

Answer

D

Explanation

Human insulin (Mol.wt 5,734) contains 51 amino acids , arranged in two polypeptide chains . The chain A has 21 amino acids while B has 30 amino acids. Both are held together by two interchain disulphide bridges , connecting `A_(7)" to "B_(7)andA_(20) " to "B_(19)`. In addition there is an intra - chain disulphide linkage in case of proinsuline.