The Peroxynitrite-mediated Oxidation of OxyMb and OxyHb

Despite the presence of a large concentration of carbon dioxide in the blood (ca. 1 him), it has been reported that peroxynitrite can diffuse across the red-blood-cell membrane and react with oxyHb [24]. The anionic form (ONOO-) crosses the erythrocyte membrane by using the anion channel band 3 whereas peroxynitrous acid crosses the lipid membranes by rapid passive diffusion [24]. 

We have recently shown that the peroxynitrite-mediated oxidation of oxyMb and oxyHb proceeds via intermediate oxoiron(iv) (ferryl) complexes, which, in a second step, react further with peroxynitrite to yield metMb and metHb, respec- 

Additional evidence for the role of oxyMb and oxyHb as scavengers of peroxynitrite is the observation that they effectively protect against peroxynitrite-mediated nitration of free tyrosine. Reaction of 200 (j.m peroxynitrite with 100 tM tyrosine leads to the formation of approximately 15% nitrotyrosine (at pH 7.4 and 20 °C). When the same reaction is carried out in the presence of 50 tM oxyMb no nitrotyrosine can be detected. In addition, the same amount of metMb reduces the 

HPLC after acid hydrolysis, from the reaction 

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