Fabian M, Thörnström P E, Brzezinski P, Malmström B G
FEBS Lett. 1987 Mar 23;213(2):396-400. doi: 10.1016/0014-5793(87)81529-6.
The resting as well as the 420 nm and 428 nm forms of cytochrome oxidase have been studied in kinetic experiments with an excess of enzyme over reduced cytochrome c. No difference was found in the behavior of the two activated forms. With all three forms, a fraction of cytochrome a was reoxidized with a rate which was much lower than kcat. This suggests that intramolecular transfer to the dioxygen-reducing site occurs only if both cytochrome a and CuA are reduced. An initial rapid phase in the oxidation of cytochrome a in the pulsed and oxygenated enzymes is related to the presence of a three-electron-reduced dioxygen intermediate. The increased catalytic activity of pulsed and oxygenated oxidase can be explained on the basis of a shift in the redox equilibrium between cytochrome a and CuA.
在酶过量于还原型细胞色素c的动力学实验中，对细胞色素氧化酶的静止形式以及420纳米和428纳米形式进行了研究。未发现两种活化形式的行为有差异。对于所有三种形式，细胞色素a的一部分以远低于催化常数（kcat）的速率被再氧化。这表明只有当细胞色素a和铜A（CuA）都被还原时，才会发生向双加氧还原位点的分子内转移。脉冲式和充氧酶中细胞色素a氧化的初始快速阶段与三电子还原双加氧中间体的存在有关。脉冲式和充氧氧化酶催化活性的增加可以基于细胞色素a和铜A之间氧化还原平衡的变化来解释。
