Dityrosine is a fluorescent biomolecule and it is a specific biomarker for oxidative stress. Though dityrosine cross link provides structural rigidity to proteins, increased level of dityrosine crosslink is associated with numerous diseased states. It is important to find out whether the local environment of Tyr has any role in determining the rate of formation of dityrosine. A detailed study has been done with substrates as C-terminal Tyr-containing dipeptides of all possible combinations. In the HRP-catalyzed oxidation of L-Tyr-containing dipeptides with H2O2, the rate of dimerization is higher for all dipeptides compared to that of free L-Tyr. When the neighbouring amino acid residue is a positively charged amino acid residue like Lys or Arg, the enhancement in rate of formation of corresponding dityrosine has been observed. With the negatively charged amino acid residues like Glu or Asp as neighbouring amino acid residues, the decrease in rate has been observed. However, no dityrosine formation has been observed with Cys-Tyr. Instead, the formation of disulfide (Tyr-Cys-Cys-Tyr) has been observed. The enhancement in rate has been observed with externally added L-Arg. The oxidation trend is likely to follow the pKa of neighbouring amino acid residue. As the pKa of L-Arg and L-Lys are higher, the rate of dityrosine formation is higher for dipeptides Arg-Tyr and Lys-Tyr. The decrease in rate of dityrosine formation of peptides Asp-Tyr and Glu-Tyr are attributed to the lower pKa of Asp and Glu, respectively. However, the appreciably higher rate of dityrosine formation of Phe-Tyr is attributed to the presence of strong hydrophobic environment around the active site of HRP