Xu F, DeFilippi L J, Ballou D P, Hultquist D E
Department of Biological Chemistry, University of Michigan, Ann Arbor 48109-0606.
Arch Biochem Biophys. 1993 Feb 15;301(1):184-9. doi: 10.1006/abbi.1993.1131.
The ferric and ferrous forms of bovine erythrocyte green hemeprotein react with hydroperoxides to form higher oxidation state intermediates with absorbance maxima in the Soret region at 426 and 422 nm, respectively. In the absence of an appropriate reductant, these intermediates undergo rapid bleaching reactions. 2,2'-Azinobis(3-ethylbenzthiazoline-6-sulfonic acid) rapidly reduces the intermediate formed by reaction of ferric green hemeprotein with hydrogen peroxide, thereby preventing bleaching and allowing the rate of the intermediate formation to be calculated from the coupled dye oxidation. This rate constant of 70 M-1 s-1 at 23 degrees C is similar to those determined by bleaching and by direct photometric detection of the intermediate. Dihydroriboflavin rapidly reduces the intermediate formed by reaction of ferrous green hemeprotein with hydrogen peroxide, thereby preventing bleaching and allowing the rate of the intermediate formation to be calculated from the coupled dihydroriboflavin oxidation; the rate constant of 2 x 10(4) M-1 s-1 at 23 degrees C is similar to the value calculated by direct detection of the intermediate. The results demonstrate that, in contrast to the reductase activity of its heme-free form, the green heme form of the protein reacts with hydroperoxides to generate highly unstable peroxide complexes.
牛红细胞绿色血红素蛋白的三价铁和二价铁形式与氢过氧化物反应，形成更高氧化态的中间体，其在索雷特区域的吸收最大值分别在426和422 nm处。在没有合适的还原剂的情况下，这些中间体发生快速的褪色反应。2,2'-联氮双(3-乙基苯并噻唑啉-6-磺酸)能快速还原三价铁绿色血红素蛋白与过氧化氢反应形成的中间体，从而防止褪色，并能根据偶联的染料氧化反应计算中间体的形成速率。在23℃下，该反应的速率常数为70 M-1 s-1，与通过褪色和直接光度检测中间体所确定的速率常数相似。二氢核黄素能快速还原二价铁绿色血红素蛋白与过氧化氢反应形成的中间体，从而防止褪色，并能根据偶联的二氢核黄素氧化反应计算中间体的形成速率；在23℃下，其速率常数为2×10(4) M-1 s-1，与直接检测中间体所计算的值相似。结果表明，与其无血红素形式的还原酶活性相反，该蛋白的绿色血红素形式与氢过氧化物反应生成高度不稳定的过氧化物复合物。
