Analysis of ferrylHb radical reduction by L-tyrosine and its application to hemoglobin vesicles

We found that a mixed solution of methemoglobin (metHb) and L-tyrosine (L-Tyr) showed an effective H₂O₂ elimination ability by utilizing the peroxidase activity of metHb using L-Tyr as a substrate. The rapid radical disappearance and the appearance of metHb signal by L-Tyr addition were confirmed in the ESR measurement. In the mechanism, ferrylHb radicals are reduced to metHb by the electron donation from L-Tyr. From these results, stable H₂O₂ elimination by metHb/L-Tyr mixed solution would be due to the combination of peroxidase and pseudo-catalase activity of ferrylHb radicals. Furthermore, in the application to the Hb vesicles co-encapsulating metHb/L-Tyr, the 50 % metHb conversion from oxyHb in the vesicles was prolonged to 44 hr from 14hr of the Hb vesicles without metHb/L-Tyr.