Hemin-H2O2-NO2− induced protein oxidation and tyrosine nitration are different from those of SIN-1: A study on glutamate dehydrogenase nitrative/oxidative modification

Protein oxidation and tyrosine nitration are two major post-translational modifications of protein by reactive nitrogen oxide species, which are mainly produced by peroxynitrite and heme peroxidases (hemin)-H2O2-NO2− system. We report herein some novel phenomena between hemin-H2O2-NO2− and 3-morpholinosydnonimine hydrochloride (SIN-1)-mediated oxidation and nitration reactions of glutamate dehydrogenase (GDH). Hemin-H2O2 could effectively induce GDH protein oxidation and reduce its activity. Although the addition of low concentration of nitrite promoted protein oxidation, protein oxidation was weakened with the increase of nitrite concentration, meanwhile, tyrosine nitration was increased and the enzyme activity was partially restored. However, with the increase of SIN-1 concentration, protein oxidation and tyrosine nitration were increased, enzyme activity was decreased. The presence of desferrioxamine and/or catechin inhibit tyrosine nitration both in hemin-H2O2-NO2− and in SIN-1, but they promoted protein oxidation and reduced the enzyme activity in hemin-H2O2-NO2− system, while inhibited protein oxidation and recover the enzyme activity in SIN-1 system. These results reveal both hemin-H2O2-NO2− and SIN-1 can cause inactivation of GDH through protein oxidation and tyrosine nitration, but the impact of the effect of protein oxidation (not thiol oxidation) on enzyme activity is stronger than that of protein tyrosine nitration. Moreover, mass spectrometric analysis indicated that nitrated tyrosine residues by hemin-H2O2-NO2− were Tyr262 and Tyr471 while by SIN-1 were Tyr401 and Tyr493. It meant that protein oxidation and tyrosine nitration of GDH induced by hemin-H2O2-NO2− were different from those induced by SIN-1.