Effects of hypotaurine on carbonate radical anion and nitrogen dioxide radical generated by peroxidase activity of Cu,Zn-superoxide dismutase

Cysteine sulfinate (CSA) and hypotaurine are recognized as key intermediates in the metabolic pathway leading from cysteine to taurine. The oxidation of sulfinic group to the respective sulfonate is a crucial point for generation of taurine in mammalian tissues. The mechanism of sulfinic group oxidation could not be related to specific enzymatic activities. However, oxidizing agents, such as hydroxyl radical, photochemically generated singlet oxygen and peroxynitrite have been reported to accomplish such oxidation in good yield. Carbonate radical anion (CO3 radical) is receiving increasing attention as important mediator of biological processes and is a potent one-electron oxidant that is able to oxidize a variety of biotargets. Nitrogen dioxide radical (NO2) is well known as a reactive species capable to initiate both oxidation and nitration reactions. The pathogenic role of radical NO2 has been related mostly to the increased level of nitrated proteins detected under many diseases