On the molecular mechanism of metmyoglobin-catalyzed reduction of hydrogen peroxide by ascorbate.
Hydrogen peroxide induces rapid oxidation of metmyoglobin with an apparent second order rate constant, k1 = 3.4 x 10(4) M-1 min-1. The product of this interaction is ferrylmyoglobin with an unstable free radical on the globin moiety. This activated form of myoglobin is able: (a) to initiate the peroxidation of erythrocyte membranes and (b) to form intra- and intermolecular covalent crosslinkings. The presence of ascorbic acid in amounts stoichiometric to H2O2 efficiently prevents all the above processes. Moreover, in the presence of ascorbic acid a cyclic process is taking place leading to H2O2 reduction, ascorbic acid oxidation, and unmodified metmyoglobin formation (reaction 1).
Galaris
D
D
Laboratory of Biological Chemistry, University of Ioannina Medical School, Greece.
Korantzopoulos
P
P
D000107:Acetylation; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D005609:Free Radicals / Q000378:metabolism; D006736:Horses; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008786:Metmyoglobin / Q000187:drug effects / Q000378:metabolism*; D009132:Muscles / Q000293:injuries / Q000378:metabolism; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D005609:Free Radicals; D017382:Reactive Oxygen Species; C028048:ferrylmyoglobin; D008786:Metmyoglobin; D014443:Tyrosine; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid