Ferryl haemoglobin

The findings here surest that, after an initial slow phase corresponding to the antioxidant capacity of the LDL, hydroperoxides can interact with haemoglobin in a similar manner to hydrogen peroxide, forming ferryl haemoglobin, which is then rapidly reduced to mixtures consisting mainly of oxy- and met- forms, possibly by the synproportionation reaction, as proposed in the studies... 

Giulivi, C. and Davies, K. (1990). A novel antioxidant role for haemoglobin. The comproportionation of ferryl haemoglobin with oxyhaemoglobin. J. Biol. Chem. 265, 19453-19460. 

The time-scale of this haem conversion is related to the antioxidant status of the LDL and that of the erythrocyte lysate. The incorporation of lipid-soluble antioxidants, such as tocopherol and butylated hydroxy-toluene (BHT) at specific time points during the LDL-erythrocyte interaction, prolongs the lag phase to oxidation, eliminates the oxy to ferryl conversion of the haemoglobin and delays the oxidative modification of the LDL. 

Although both haemoglobin [155,231] and myoglobin produce ferryl iron and free radicals upon addition of H2O2, the latter reaction has been studied more extensively. In contrast to most peroxidases, at least two myoglobin-bound free radicals have been detected immediately after peroxide addition, both by room-temperature [142] and low-temperature EPR[137]. These decay rapidly and independently of the decay of the ferryl iron, which is stable for at least an hour. It is not necessary to add exogenous reductants to reduce the radicals it is possible that some of the electrons come from elsewhere on the protein as different, more stable, free radicals can be detected one hour subsequent to peroxide treatment [137,236]. 

EPR spectroscopy has demonstrated that the oxidation of the globin occurs ultimately at a tyrosine residue, resulting in the formation of a tyrosine-phenoxyl radical this species is postulated to react subsequently with oxygen to give a tyrosine-peroxyl radical. Studies have shown that both of these species are accessible to components in bulk solution, i.e. they are located on the surface of the protein [47-49]. Ferryl haem protein radical from myoglobin and haemoglobin can react with membranes [33,45,50] and lipoproteins [51-... 

---