Wazawa T, Matsuoka A, Tajima G, Sugawara Y, Nakamura K, Shikama K
Biological Institute, Faculty of Science, Tohoku University, Sendai, Japan.
Biophys J. 1992 Aug;63(2):544-50. doi: 10.1016/S0006-3495(92)81608-9.
The stability properties of the iron(II)-dioxygen bond in myoglobin and hemoglobin are of particular importance, because both proteins are oxidized easily to the ferric met-form, which cannot be oxygenated and is therefore physiologically inactive. In this paper, we have formulated all the possible pathways leading to the oxidation of myoglobin to metmyoglobin with each required rate constant in 0.1 M buffer (pH 7.0) at 25 degrees C, and have set up six rate equations for the elementary processes going on in a simultaneous way. By using the Runge-Kutta method to solve these differential equations, the concentration progress curves were then displayed for all the reactive species involved. In this complex reaction, the primary event was the autoxidation of MbO2 to metMb with generation of the superoxide anion, this anion being converted immediately and almost completely into H2O2 by the spontaneous dismutation. Under air-saturated conditions (PO2 = 150 Torr), the H2O2 produced was decomposed mostly by the metMb resulting from the autoxidation of MbO2. At lower pressures of O2, however, H2O2 can act as the most potent oxidant of the deoxyMb, which increases with decreasing O2 pressures, so that there appeared a well defined maximum rate in the formation of metMb at approximately 5 Torr of oxygen. Such examinations with the aid of a computer provide us, for the first time, with a full picture of the oxidation reaction of myoglobin as a function of oxygen pressures. These results also seem to be of primary importance from a point of view of clinical biochemistry of the oxygen supply, as well as of pathophysiology of ischemia, in red muscles such as cardiac and skeletal muscle tissues.
肌红蛋白和血红蛋白中铁（II）-双氧键的稳定性尤为重要，因为这两种蛋白质都很容易被氧化成高铁形式，而高铁形式无法被氧合，因此生理上无活性。在本文中，我们已列出了在25℃、0.1M缓冲液（pH 7.0）中肌红蛋白氧化为高铁肌红蛋白的所有可能途径以及每个所需的速率常数，并为同时发生的基本过程建立了六个速率方程。通过使用龙格-库塔方法求解这些微分方程，然后显示了所有相关反应物种的浓度变化曲线。在这个复杂反应中，主要事件是MbO₂自氧化为高铁肌红蛋白并生成超氧阴离子，该阴离子通过自发歧化立即几乎完全转化为H₂O₂。在空气饱和条件下（PO₂ = 150 Torr），产生的H₂O₂大部分被MbO₂自氧化产生的高铁肌红蛋白分解。然而，在较低的氧气压力下，H₂O₂可作为脱氧肌红蛋白的最有效氧化剂，其随着氧气压力的降低而增加，因此在约5 Torr氧气下高铁肌红蛋白的形成出现了明确的最大速率。借助计算机进行的此类研究首次为我们提供了肌红蛋白氧化反应随氧气压力变化的全貌。从心脏和骨骼肌组织等红色肌肉中氧气供应的临床生物化学以及缺血病理生理学的角度来看，这些结果似乎也具有首要意义。
