Time evolution of the intermediates formed in the reaction of oxygen with mixed-valence cytochrome c oxidase
Time evolution of the intermediates formed in the reaction of oxygen with mixed-valence cytochrome c oxidase
复制标题
氧与混合价细胞色素c氧化酶反应形成中间体的时间演化
DOI：
10.1021/ja00182a001
复制
发表时间：
1990
影响因子：
15
通讯作者：
D. Rousseau
中科院分区：
文献类型：
--
作者：
Sanghwa Han;Y. Ching;D. Rousseau
通过监测共振拉曼和光学吸收光谱与流动闪光探针技术的混合价态细胞色素c氧化酶的氧反应中形成的中间体作为时间的函数。在早期（50 ms），光学吸收光谱证实了初级中间体（Im）的存在。该中间体在共振拉曼光谱中在568 cm-1处具有Fe-02伸缩模式，其用作其布居的标记。通过跟踪该模式的强度变化，测得Im衰减的一级速率常数为4.5 × 103 s-1。下一个中间体（IIm）的形成与607-nm的光吸收差光谱中的峰的酶进行了监测，其光吸收光谱，并显示其形成的一级速率常数，这是相同的衰减Im的速率常数。Im和IIm的共振拉曼光谱几乎相同，表明这两种中间体的细胞色素a 3中卟啉大环的tr-电子耗尽是相同的。通过将氧与CO结合的混合价细胞色素c氧化酶混合并允许O2自发地替代CO而形成的中间体的吸收光谱和共振拉曼光谱与光解实验中形成的IIm的吸收光谱和共振拉曼光谱相同。以这种方式形成的11 m双相衰变为酶的静息形式。
The intermediates formed in the reaction of oxygen with mixed-valence cytochrome c oxidase were followed as a function of time by monitoring the resonance Raman and optical absorption spectra with a flow-flash-probe technique. At early times (50 ms), the optical absorption spectra confirm the presence of the primary intermediate (Im). This intermediate has an Fe-02 stretching mode in the resonance Raman spectrum at 568 cm" 1 that was used as a marker for its population. By following the change in intensity of this mode, the first-order rate constant for the decay of Im was measured to be 4.5 X 103 s'1. The formationof the next intermediate (IIm) of the enzyme with a 607-nm peak in the optical absorption difference spectrum was monitored by its optical absorption spectrum and displays a first-order rate constant for its formation, which is the same as the rate constant for the decay Im. The resonance Raman spectrum of Im and IIm are nearly identical, indicating that the tr-electron depletion of the porphyrin macrocycle in cytochrome a3 is the same for these two intermediates. The absorption spectrum and the resonance Raman spectrum of an intermediate formed by mixing oxygen with CO-bound mixed-valence cytochrome c oxidase and allowing 02 to spontaneously replace CO are the same as those of IIm formed in the photolysis experiments. llm, formed in this way, decays biphasically to the resting form of the enzyme.