Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, Cluj-Napoca, Romania.
Faculty of Chemistry and Chemical Engineering, Babes-Bolyai University, Cluj-Napoca, Romania.
Free Radic Biol Med. 2019 Jun;137:110-115. doi: 10.1016/j.freeradbiomed.2019.04.034. Epub 2019 Apr 26.
Hemoglobin in its ferryl form oxidizes hydrogen sulfide and is transformed to sulfhemoglobin, where the sulfur is inserted covalently at the heme edge. Shown here is evidence that-as previously proposed by others-this process involves oxidation of hydrogen sulfide to a sulfanyl radical detectable by spin-trapping in electron paramagnetic resonance (EPR) spectroscopy. The yields and rates of formation of sulfhemoglobin as well as of the sulfanyl radical are affected by the same factors that affect the reactivity of hemoglobin ferryl, in bovine hemoglobin and in phytoglobins as well. A freely-diffusing sulfanyl radical is thus proposed to be involved in sulfhemoglobin formation. Catalase is shown to accelerate this process due to a previously described hydrogen sulfide oxidase activity, within which EPR evidence for sulfanyl generation is shown here for the first time. The reaction of preformed ferryl with hydrogen sulfide-in absence of hydrogen peroxide-is studied by stopped-flow at several pH values and explained in light of reactivity and redox potential control.
亚铁血红蛋白氧化硫化氢，并转化为硫血红蛋白，其中硫通过共价键插入卟啉边缘。这里显示的证据表明——如其他人之前提出的那样——这个过程涉及到硫化氢被氧化成硫自由基，可通过电子顺磁共振（EPR）光谱中的自旋捕获检测到。硫血红蛋白以及硫自由基的产率和形成速率受到同样的因素影响，这些因素也会影响亚铁血红蛋白的反应活性，无论是在牛血红蛋白还是植物血球蛋白中都是如此。因此，我们提出一种自由扩散的硫自由基参与了硫血红蛋白的形成。过氧化氢酶由于先前描述的硫化氢氧化酶活性而加速了这个过程，这里首次展示了 EPR 证据表明该酶生成了硫自由基。在几种 pH 值下通过停流实验研究了预形成的亚铁与硫化氢的反应——在没有过氧化氢的情况下——并根据反应活性和氧化还原电位控制进行了解释。
