Kinetics and mechanism of oxidation of cachalot oxymyoglobin catalyzed by potassium ferrocyanide

The mechanism of the oxidation of cachalot oxymyoglobin (MbO(2)) catalyzed by small amounts (1-20% of the protein content) of potassium ferri- and fer rocyanides was studied. It was shown that the mechanism of the catalysis in volves a specific binding of the ferrocyanide anion with protein. The effec ts on the reaction rate of the pH and ionic strength of the medium, the [Fe (CN)(6)](4-) concentration, and the formation of myoglobin (Mb) complexes w ith redox-inert zinc ions [which form (at the equimolar concentration) stab le complexes with His 119(GH1) on the protein molecule surface] were examin ed. The kinetic scheme of the reaction was analyzed and its equilibrium and kinetic parameters were determined. It was shown for the first time that p otassium ferricyanide, a strong oxidant, can catalyze the oxidation of oxym yoglobin and react with protein via two mechanisms simultaneously: via a si mple extraspheric interaction with the hemic group and through the formatio n of a specific [Fe(CN)(6)](4-) protein complex.