Proton pumping by cytochrome oxidase: progress, problems and postulates.
Proton pumping by cytochrome oxidase: progress, problems and postulates.
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DOI：
10.1016/s0005-2728(00)00066-9
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发表时间：
2000-05
期刊：
影响因子：
--
通讯作者：
D. Zaslavsky;R. Gennis
中科院分区：
文献类型：
--
作者：
D. Zaslavsky;R. Gennis
讨论了细胞色素氧化酶质子泵机制的研究现状。细菌氧化酶质子传导途径的定点突变研究取得了重大进展。似乎有两个通道，以促进质子易位的酶，他们是重要的催化循环的不同部分。使用过氧化氢作为替代底物提供了一个非常有用的实验工具，探索该系统的酶学，并从这种方法获得的见解进行了描述。质子转移耦合到，并出现调节周转过程中的电子转移步骤的速率。有人提出，在反应的初始步骤涉及质子转移到活性位点，这是重要的金属连接的氢氧化物转化为水，它可以更迅速地从金属解离，并允许与分子氧的反应，我们建议，可以绑定的单电子还原血红素铜中心。质子和电子在酶内短距离和长距离的协调运动似乎在催化循环的不同部分都很重要。在最初的还原过程中的分子氧，直接氢转移形成酪氨酰基自由基的活性位点似乎是可能的。随后的步骤可以通过蛋白质表面残基的突变来有效地阻断，显然阻止了质子的进入。
The current status of our knowledge about the mechanism of proton pumping by cytochrome oxidase is discussed. Significant progress has resulted from the study of site-directed mutants within the proton-conducting pathways of the bacterial oxidases. There appear to be two channels to facilitate proton translocation within the enzyme and they are important at different parts of the catalytic cycle. The use of hydrogen peroxide as an alternative substrate provides a very useful experimental tool to explore the enzymology of this system, and insights gained from this approach are described. Proton transfer is coupled to and appears to regulate the rate of electron transfer steps during turnover. It is proposed that the initial step in the reaction involves a proton transfer to the active site that is important to convert metal-ligated hydroxide to water, which can more rapidly dissociate from the metals and allow the reaction with dioxygen which, we propose, can bind the one-electron reduced heme-copper center. Coordinated movement of protons and electrons over both short and long distances within the enzyme appear to be important at different parts of the catalytic cycle. During the initial reduction of dioxygen, direct hydrogen transfer to form a tyrosyl radical at the active site seems likely. Subsequent steps can be effectively blocked by mutation of a residue at the surface of the protein, apparently preventing the entry of protons.