Kosaka H, Tyuma I
Department of Physicochemical Physiology, Medical School, Osaka University, Japan.
Environ Health Perspect. 1987 Aug;73:147-51. doi: 10.1289/ehp.8773147.
Oxidation of oxyhemoglobin by nitrite is characterized by the presence of a lag phase followed by autocatalysis. The stoichiometry of the overall reaction is described by the following equation: 4HbO2 + 4NO2- + 4H+ = 4Hb+ + 4NO3- + O2 + 2H2O (Hb denotes hemoglobin monomer). During the oxidation, we detected a free radical at g = 2.005, which is very similar to the methemoglobin free radical generated by the reaction with hydrogen peroxide. Nitrosylhemoglobin was not detected. The oxidation was delayed by the addition of KCN or catalase, but was not modified by superoxide dismutase in phosphate buffer. In bistris buffer, however, superoxide dimutase markedly prolonged the lag phase. The results suggest that during the oxidation, the methemoglobin peroxide compound is generated and converts nitrite into nitrogen dioxide by its peroxidatic activity. Nitrogen dioxide oxidizes oxyhemoglobin to methemoglobin and nitrite, yielding the autocatalytic phase.
亚硝酸盐对氧合血红蛋白的氧化作用具有一个滞后阶段，随后是自催化过程。整个反应的化学计量关系由以下方程式描述：4HbO₂ + 4NO₂⁻ + 4H⁺ = 4Hb⁺ + 4NO₃⁻ + O₂ + 2H₂O（Hb表示血红蛋白单体）。在氧化过程中，我们在g = 2.005处检测到一个自由基，它与过氧化氢反应生成的高铁血红蛋白自由基非常相似。未检测到亚硝酰血红蛋白。在磷酸盐缓冲液中，加入KCN或过氧化氢酶会延迟氧化，但超氧化物歧化酶对其无影响。然而，在双三羟甲基氨基甲烷缓冲液中，超氧化物歧化酶显著延长了滞后阶段。结果表明，在氧化过程中，会生成高铁血红蛋白过氧化物化合物，其过氧化物酶活性将亚硝酸盐转化为二氧化氮。二氧化氮将氧合血红蛋白氧化为高铁血红蛋白和亚硝酸盐，从而产生自催化阶段。
