Formation of fluorescent heme degradation products during the oxidation of hemoglobin by hydrogen peroxide

Hemoglobin and methemoglobin oxidized by hydrogen peroxide generate ferrylhemoglobin and oxoferrylhemoglobin, respectively. Two fluorescent compounds were found to be produced during the reaction of oxyhemoglobin, but not methemoglobin, with H₂O₂. These two compounds had excitation wavelengths of 321 nm and 460 nm, respectively, with emission wavelengths of 465 nm and 525 nm, respectively. The formation of the same fluorescent products during the reaction of H₂O₂ with ferroprotoporphyrin-IX and ferriprotoporphyrin-IX demonstrate that these compounds originate from the heme moiety. The release of heme iron during the formation of these fluorescent compounds indicates that they are associated with heme degradation. The time course for the formation of fluorescent products show that the extent of heme degradation is dependent on H₂O₂ concentration. The results of this investigation indicate that the heme moiety of Fe(II) hemoglobin undergoes degradation in presence of H₂O₂. The ability to detect this process by fluorescence provides a sensitive marker in order to asses hemoglobin and RBC oxidative stress under pathological conditions.