Enzymatic elimination of hydrogen peroxide by a methemoglobin/L-Tyrosine system.
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.
Atoji
Tomoyasu
T
Department of Applied Chemistry, Graduate School of Science and Engineering, Waseda University, Tokyo, Japan.
Yatami
Hirotaka
H
Aihara
Motonari
M
Takeoka
Shinji
S
D006454:Hemoglobins / Q000737:chemistry / Q000302:isolation & purification; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008706:Methemoglobin / Q000138:chemical synthesis / Q000378:metabolism*; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*; D013696:Temperature; D014443:Tyrosine / Q000378:metabolism*
D006454:Hemoglobins; C517773:ferrylhemoglobin; D014443:Tyrosine; D008706:Methemoglobin; D006861:Hydrogen Peroxide; D009195:Peroxidase