Ferrocyanide - a novel catalyst for oxymyoglobin oxidation by molecular oxygen.

A comparative study of the rates of ferrocyanide-catalyzed oxidation of several oxymyoglobins by molecular oxygen is reported. Oxidation of the native oxymyoglobins from sperm whale, horse and pig, as well as the chemically modified (MbO(2)) sperm whale oxymyoglobin, with all accessible His residues alkylated by sodium bromoacetate (CM-MbO(2)), and the mutant sperm whale oxymyoglobin [MbO(2)(His119-->Asp)], was studied. The effect of pH, ionic strength and the concentration of anionic catalyst ferrocyanide, [Fe(CN)(6)](4-), on the oxidation rate is investigated, as well as the effect of MbO(2) complexing with redox-inactive Zn(2+), which forms the stable chelate complex with functional groups of His119, Lys16 and Asp122, all located nearby.

[The mechanism of oxymyoglobin oxidation catalyzed by ferrocyanide ions: chemically modified and mutant sperm whale myoglobins].

A comparative study of the rate of ferrocyanide-catalyzed oxidation of native sperm whale MbO2, its chemically modified derivative in which all accessible His residues are alkylated by sodium bromoacetate, (CM-MbO2), and mutant sperm whale MbO2 with His119 replaced by Asp residiue, [MbO2(His119-->Asp)] was carried out. The influence of pH, ionic strength, and [Fe(CN)6]4- concentration on the oxidation rate was investigated, as well as the effect of complexing MbO2 with redox-inactive Zn2+ ion, which, at the equimolar Zn2+ concentration, forms a stable complex with His119(GH1) on the protein surface. It was shown that the mechanism of the catalysis involves specific binding of [Fe(CN)6]4- to the protein at the His119(GH1) region, which is in agreement with a large positive electrostatic potential and the presence at this site of Mb of a cavity large enough to accommodate [Fe(CN)6]4- anion.

[The oxidation of sperm whale, horse, and pig oxymyoglobins, catalyzed by ferrocyanide ions: kinetics and mechanism].

The influence of pH, ionic strength of the solution, and [Fe(CN)6]4- concentration on the rate of oxidation of sperm whale, horse, and pig oxymyoglobins, which is catalyzed by ferrocyanide ions, was studied. These myoglobins have homologous spatial structures and identical redox potentials but differ by the amount of His residues located on the protein surface. The effect of the MbO2 complexing with redox-inactive Zn2+ ion on the reaction rate was also examined.