Kosaka H, Tyuma I, Imaizumi K
Biomed Biochim Acta. 1983;42(11-12):S144-8.
Oxidation of oxyhemoglobin by nitrite is characterized by the presence of a lag phase followed by the autocatalysis. In phosphate buffer, an asymmetric ESR signal is detected at g = 2.005 (hereafter referred to as the g = 2 radical) during the oxidation which is similar to that of the methemoglobin free radical generated from methemoglobin and H2O2. Catalase and KCN prolong the oxidation, indicating the involvement of H2O2 and methemoglobin in the reaction. Superoxide dismutase, on the other hand, does not modify the oxidation. The present results suggest a chain reaction mechanism for the oxidation in which the g = 2 radical catalyzes the formation of NO.2 from NO-2 by a peroxidase action and NO.2 oxidizes oxyhemoglobin. However, in N,M-bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane (bistris) buffer, superoxide dismutase markedly elongates the lag phase and accelerates the autocatalysis: bistris scavenges the g = 2 radical and a radical derived from bistris reduces O2 to O-2.
亚硝酸对氧合血红蛋白的氧化作用的特点是存在一个延迟期，随后是自催化作用。在磷酸盐缓冲液中，氧化过程中在g = 2.005处检测到一个不对称的电子自旋共振信号（以下称为g = 2自由基），这与由高铁血红蛋白和H2O2产生的高铁血红蛋白自由基的信号相似。过氧化氢酶和KCN会延长氧化时间，表明反应中涉及H2O2和高铁血红蛋白。另一方面，超氧化物歧化酶不会改变氧化过程。目前的结果表明氧化反应存在链式反应机制，其中g = 2自由基通过过氧化物酶作用催化从NO-2形成NO.2，并且NO.2氧化氧合血红蛋白。然而，在N，N-双（2-羟乙基）亚氨基三（羟甲基）甲烷（bistris）缓冲液中，超氧化物歧化酶显著延长延迟期并加速自催化作用：bistris清除g = 2自由基，并且来自bistris的一个自由基将O2还原为O-2。
