Peroxynitrite-mediated oxidation of ferrous carbonylated myoglobin is limited by carbon monoxide dissociation.
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)x10(-2)s(-1) and k(off(CO))=(1.4+/-0.2)x10(-2)s(-1), respectively, at pH 7.2 and 20.0 degrees C. The coincidence of values of h and k(off(CO)) indicates that CO dissociation represents the rate limiting step of peroxynitrite-mediated oxidation of Mb(II)-CO.
Ascenzi
Paolo
P
Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, Viale Guglielmo Marconi 446, I-00146 Roma, Italy. ascenzi@bio.uniroma3.it
Ciaccio
Chiara
C
Coletta
Massimo
M
D000818:Animals; D002248:Carbon Monoxide / Q000378:metabolism*; D006736:Horses; D007501:Iron / Q000378:metabolism*; D007700:Kinetics; D009211:Myoglobin / Q000378:metabolism*; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000378:metabolism*; D050050:Protein Carbonylation
D009211:Myoglobin; D030421:Peroxynitrous Acid; D002248:Carbon Monoxide; D007501:Iron