
%0 Journal Article
%A King, NK 
%A Winfield, ME 
%T Oxygen uptake and evolution by iron porphyrin enzymes
%J Australian Journal of Chemistry
%D 1959/03/01
%V 12
%N 1
%P 47-64
%K 
%R https://doi.org/10.1071/CH9590047
%U https://www.publish.csiro.au/paper/CH9590047 
%X Three detailed mechanisms are considered for the catalatic decomposition of H2O2. It is shown that the first of these, akin to the earlier hypotheses for catalase action, cannot satisfy the magnetic, titrimetric, and kinetic evidence. The second mechanism involves oxidation of the FeIII porphyrin to the equivalent of FeV. The electron deficiency is distributed over the ligands so that even in the most oxidized complex the iron is in the FeIV or possibly even the FeIII state. In the third scheme it is suggested that the reduction step (in which O2 is liberated) takes place at a carbon atom, while the site of the oxidation is the metal atom as commonly supposed.   The liberation of O2 from H2O2 can be catalysed by 6-coordinate ruthenium II complexes. In the catalytic cycle, the metal appears to be oxidized to Rdv, then reduced to RuII. Ethanol or ascorbic acid can substitute for H2O2 in the reduction. Evidence for H2O2 attack on the ligands is suggestive but not conclusive.   A brief comment is made on the bonding of oxygen to haemoglobin and myoglobin.   The accumulated evidence for the structures of catalase, peroxidase, and myoglobin complexes is utilized in a scheme for the uptake of oxygen by cytochrome oxidase. 
