Investigation on insulin tyrosine modification mediated by peroxynitrite

Peroxynitrite (ONOO), the product of superoxide (O₂ ^-) and nitric oxide (NO), has been implicated in diabetes and diabetic cardiovascular complications. Insulin, a mediator of these pathological processes, has an important role to maintain human blood glucose levels, and may be a potential target during accumulating ONOO^- is formed in β-cells. ONOO^- can inhibit the biological activity of insulin and affect its receptor binding capacities by modifying protein tyrosine residues. Herein, we analyzed the dose-dependent insulin tyrosine modification indicated by spectral changes. Also, the nitrated sites of insulin were identified by HPLC-MS analysis. The results show that an infusion of ONOO^- caused a maximum observed yield of 2.7 3-nitrotyrosine per insulin subunit and led to different nitrated species. Moreover, Try-B26 appeared to be the most susceptible residue concerning with ONOO mediated nitration.