Enzymatic elimination of hydrogen peroxide by a methemoglobin/L-tyrosine system

Tomoyasu Atoji, Hirotaka Yatami, Motonari Aihara, Shinji Takeoka*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


We studied the peroxidase activity of ferrylhemoglobin radical (Hb(Fe4+ = O*)) generated by the reaction of metHb (Hb(Fe3+)) with hydrogen peroxide (H2O2). To clarify the behaviors of ferrylHb radical, it was isolated from the reaction mixture of metHb and H2O2 by GPC at 4°C. The radical species underwent rapid autoreduction to metHb at 37°C accompanied with denaturation; however, it was stable for several minutes at 4°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°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 H2O2 in this system.

Original languageEnglish
Pages (from-to)555-567
Number of pages13
JournalArtificial Cells, Blood Substitutes, and Biotechnology
Issue number6
Publication statusPublished - 2007 Nov


  • Ferrylhemoglobin radical
  • Hemoglobin vesicle
  • Hydrogen peroxide
  • L-Tyrosine
  • Methemoglobin
  • Peroxidase activity

ASJC Scopus subject areas

  • Biotechnology
  • Biomedical Engineering


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