Atoji Tomoyasu, Yatami Hirotaka, Aihara Motonari, Takeoka Shinji
Department of Applied Chemistry, Graduate School of Science and Engineering, Waseda University, Tokyo, Japan.
Artif Cells Blood Substit Immobil Biotechnol. 2007;35(6):555-67. doi: 10.1080/10731190701730180.
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.
我们研究了高铁血红蛋白（Hb(Fe(3+))）与过氧化氢（H₂O₂）反应生成的高铁血红蛋白自由基（Hb(Fe(4+)=O*)）的过氧化物酶活性。为了阐明高铁血红蛋白自由基的行为，在4℃下通过凝胶渗透色谱法（GPC）从高铁血红蛋白和H₂O₂的反应混合物中分离出该自由基。该自由基物种在37℃下伴随着变性迅速自动还原为高铁血红蛋白；然而，它在4℃下可稳定存在几分钟。在电子顺磁共振（ESR）测量中，高铁血红蛋白自由基的信号在L-酪氨酸（L-Tyr）存在下立即消失，同时，高铁血红素的信号增强。这表明即使在4℃下，高铁血红蛋白自由基也会立即被L-Tyr转化为高铁血红蛋白。此外，在反应混合物中检测到了二聚化的L-Tyr。这表明高铁血红蛋白自由基通过L-Tyr的电子供体作用被还原为高铁血红蛋白。在该系统中，以L-Tyr为底物的酶促反应导致H₂O₂的消除。
