title: Ferricyanide-mediated oxidation of ferrous nitrosylated sperm whale myoglobin involves the formation of the ferric nitrosylated intermediate.
abstract: Ferricyanide-mediated oxidation of ferrous oxygenated and carbonylated myoglobin (Mb(II)-O(2) and Mb(II)-CO, respectively) is limited by O(2) and CO dissociation, respectively, then the transient deoxygenated derivative (Mb(II)) is rapidly oxidized. Here, kinetics of ferricyanide-mediated oxidation of ferrous nitrosylated sperm whale myoblobin (Mb(II)-NO) is reported. Unlike for Mb(II)-O(2) and Mb(II)-CO, ferricyanide reacts with Mb(II)-NO forming first a transient ferric nitrosylated species (Mb(III)-NO), followed by the ()NO dissociation from Mb(III)-NO. Values of the second-order rate constant for ferricyanide-mediated oxidation of Mb(II)-NO (i.e., for the formation of the transient Mb(III)-NO species) and of the first-order rate constant for ()NO dissociation from Mb(III)-NO (i.e., for Mb(III) formation) are (1.3+/-0.2)x10(6)M(-1)s(-1) and 7.6+/-1.3s(-1), respectively, at pH 8.3 and 20.0 degrees C. Since ()NO dissociation from Mb(II)-NO is very slow, and (unlike O(2) and CO) ()NO is a ligand for both Mb(II) and Mb(III), Mb(II)-NO can be oxidized without requiring ()NO dissociation.
authors.affiliation: Department of Biology and Interdepartmental Laboratory for Electron Microscopy, University Roma Tre, Viale Guglielmo Marconi 446, I-00146 Roma, Italy. ascenzi@bio.uniroma3.it
authors.forename: Paolo
authors.initials: P
authors.lastname: Ascenzi
authors.forename: Giovanni
authors.initials: G
authors.lastname: Petrella
authors.forename: Massimo
authors.initials: M
authors.lastname: Coletta
mesh_terms: D000818:Animals; D003198:Computer Simulation; D005292:Ferricyanides / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D009211:Myoglobin / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D050661:Sperm Whale / Q000378:metabolism*
chemical_list: D005292:Ferricyanides; D009211:Myoglobin; C007931:hexacyanoferrate III; D009569:Nitric Oxide