The number of disulphide linkage present in insulin are 

 . Integral to insulin's structure are its three disulfide bonds — one intra-chain (Cys^A6-Cys^A11) and two inter-chain (Cys^A7-Cys^B7 and Cys^A20-Cys^B19) (Fig. 1a). Formation of these disulfide linkages ensures both the correct folding of the insulin precursor polypeptide and the structural stability of the mature hormone