[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 protonation of nearby His113 and His116 residiues (especially of the latter) plays a very important role in the catalysis, promoting the fast oxidation of bound [Fe(CN)6]4- by dissolved oxygen. Only the presence of these both necessary conditions in MbO2 structure provides its effective oxydation catalyzed by ferrocyanide.
Shekhovtsova
E A
EA
Goraev
E V
EV
Sivozhelezov
V S
VS
Postnikova
G B
GB
D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D002384:Catalysis; D005295:Ferrocyanides / Q000737:chemistry*; D008786:Metmyoglobin / Q000737:chemistry* / Q000235:genetics; D009211:Myoglobin / Q000737:chemistry* / Q000235:genetics; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D017354:Point Mutation; D014907:Whales / Q000235:genetics
D005295:Ferrocyanides; D009211:Myoglobin; C017595:oxymyoglobin; D008786:Metmyoglobin; C020354:hexacyanoferrate II; D010100:Oxygen