Peroxynitrite scavenging by ferryl sperm whale myoglobin and human hemoglobin

Globins protect from the oxidative and nitrosative cell damage. Here, kinetics of peroxynitrite scavenging by ferryl sperm whale myoglobin (Mb{single bond}Fe(IV){double bond, long}O) and human hemoglobin (Hb{single bond}Fe(IV){double bond, long}O), between pH 5.8 and 8.3 at 20.0 °C, are reported. In the absence of CO2, values of the second-order rate constant for peroxynitrite scavenging by Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O (i.e., for Mb{single bond}Fe(III) and Hb{single bond}Fe(III) formation; kon) are 4.6 × 104 M-1 s-1 and 3.3 × 104 M-1 s-1, respectively, at pH 7.1. Values of kon increase on decreasing pH with pKa values of 6.9 and 6.7, this suggests that the ONOOH species reacts preferentially with Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O. In the presence of CO2 (=1.2 × 10-3 M), values of kon for peroxynitrite scavenging by Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O are essentially pH-independent, the average kon values are 7.1 × 104 M-1 s-1 and 1.2 × 105 M-1 s-1, respectively. As a whole, Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O, obtained by treatment with H2O2, undertake within the same cycle H2O2 and peroxynitrite detoxification. © 2009 Elsevier Inc. All rights reserved

Peroxynitrite scavenging by ferryl sperm whale myoglobin and human hemoglobin

Globins protect from the oxidative and nitrosative cell damage. Here, kinetics of peroxynitrite scavenging by ferryl sperm whale myoglobin (Mb{single bond}Fe(IV){double bond, long}O) and human hemoglobin (Hb{single bond}Fe(IV){double bond, long}O), between pH 5.8 and 8.3 at 20.0 °C, are reported. In the absence of CO2, values of the second-order rate constant for peroxynitrite scavenging by Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O (i.e., for Mb{single bond}Fe(III) and Hb{single bond}Fe(III) formation; kon) are 4.6 × 104 M-1 s-1 and 3.3 × 104 M-1 s-1, respectively, at pH 7.1. Values of kon increase on decreasing pH with pKa values of 6.9 and 6.7, this suggests that the ONOOH species reacts preferentially with Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O. In the presence of CO2 (=1.2 × 10-3 M), values of kon for peroxynitrite scavenging by Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O are essentially pH-independent, the average kon values are 7.1 × 104 M-1 s-1 and 1.2 × 105 M-1 s-1, respectively. As a whole, Mb{single bond}Fe(IV){double bond, long}O and Hb{single bond}Fe(IV){double bond, long}O, obtained by treatment with H2O2, undertake within the same cycle H2O2 and peroxynitrite detoxification. © 2009 Elsevier Inc. All rights reserved