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  • Title: Enzymatic elimination of hydrogen peroxide by a methemoglobin/L-Tyrosine system.
    Author: Atoji T, Yatami H, Aihara M, Takeoka S.
    Journal: Artif Cells Blood Substit Immobil Biotechnol; 2007; 35(6):555-67. PubMed ID: 18097784.
    Abstract:
    We studied the peroxidase activity of ferrylhemoglobin radical (Hb(Fe(4+) = O*)) generated by the reaction of metHb (Hb(Fe(3+))) with hydrogen peroxide (H(2)O(2)). To clarify the behaviors of ferrylHb radical, it was isolated from the reaction mixture of metHb and H(2)O(2) by GPC at 4 degrees C. The radical species underwent rapid autoreduction to metHb at 37 degrees C accompanied with denaturation; however, it was stable for several minutes at 4 degrees C. In ESR measurements, the signal of the ferrylHb radical immediately disappeared in the presence of L-Tyrosine (L-Tyr), and simultaneously, the signal of the ferric heme increased. This suggested that the ferrylHb radical immediately converted to metHb by L-Tyr even at 4 degrees C. Furthermore, dimerized L-Tyr was detected in the reaction mixture. This showed that the ferrylHb radical was reduced to metHb by electron donation from L-Tyr. The enzymatic reaction using L-Tyr as the substrate resulted in the elimination of H(2)O(2) in this system.
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