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Peroxynitrite-mediated oxidation of ferrous carbonylated myoglobin is limited by carbon monoxide dissociation |
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| Authors: | Ascenzi Paolo Ciaccio Chiara Coletta Massimo |
| Institution: | a Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University ‘Roma Tre’, Viale Guglielmo Marconi 446, I-00146 Roma, Italy b National Institute for Infectious Diseases I.R.C.C.S. ‘Lazzaro Spallanzani’, Via Portuense 292, I-00149 Roma, Italy c Department of Experimental Medicine and Biochemical Sciences, University of Roma ‘Tor Vergata’, Via Montpellier 1, I-00133 Roma, Italy d Interuniversity Consortium for the Research on the Chemistry of Metals in Biological Systems (CIRCMSB), Piazza Umberto I 1, I-87100 Bari, Italy |
| Abstract: | Peroxynitrite-mediated oxidation of ferrous nitrosylated myoglobin (Mb(II)-NO) involves the transient ferric nitrosylated species (Mb(III)-NO), followed by  NO dissociation and formation of ferric myoglobin (Mb(III)). In contrast, peroxynitrite-mediated oxidation of ferrous oxygenated myoglobin (Mb(II)-O2) involves the transient ferrous deoxygenated and ferryl derivatives (Mb(II) and Mb(IV) O, respectively), followed by Mb(III) formation. Here, kinetics of peroxynitrite-mediated oxidation of ferrous carbonylated horse heart myoglobin (Mb(II)-CO) is reported. Values of the first-order rate constant for peroxynitrite-mediated oxidation of Mb(II)-CO (i.e., for Mb(III) formation) and of the first-order rate constant for CO dissociation from Mb(II)-CO (i.e., for Mb(II) formation) are h = (1.2 ± 0.2) × 10−2 s−1 and koff(CO) = (1.4 ± 0.2) × 10−2 s−1, respectively, at pH 7.2 and 20.0 °C. The coincidence of values of h and koff(CO) indicates that CO dissociation represents the rate limiting step of peroxynitrite-mediated oxidation of Mb(II)-CO. |
| Keywords: | Mb myoglobin |
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