Unusual peroxidase activity of polynitroxylated pegylated hemoglobin: Elimination of H2O2 coupled with intramolecular oxidation of nitroxides

► Polynitroxylated hemoglobin (Hb) in oxidized and reduced forms exhibit peroxidase activity. ► In plasma, ascorbate reduces polynitroxylated Hb. ► Elimination of H2O2 by reduced polynitroxylated Hb is at the expense of its reduced nitroxides. ► Both forms of polynitroxylated Hb protect SH-SY5Y cells from H2O2 toxicity.