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KINETIC TRAPPING OF OXYGEN IN CELL RESPIRATION

机译：氧在细胞呼吸中的运动学诱捕

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CELL respiration in eukaryotes is catalysed by the mitochondri`al enzyme cytochrome c oxidase. In bacteria there are many variants of this enzyme, all of which have a binuclear haem iron-copper centre at which O-2 reduction occurs, and a low-spin haem, which serves as the immediate electron donor to this centre(1). It is essential that the components of the cell respiratory system have a high affinity for oxygen because of the low concentrations of dissolved O-2 in the tissues; however, the binding of O-2 to the respiratory haem-copper oxidases is very weak(2,3). This paradox has been attributed to kinetic trapping during fast reactions of O-2 bound within the enzyme's binuclear haem iron-copper centre(2). Our earlier work(3) indicated that electron transfer from the low-spin haem to the oxygen-bound binuclear centre may be necessary for such kinetic oxygen trapping. Here we show that a specific decrease of this haem-haem electron transfer rate in the respiratory haem-copper oxidase from Escherichia coli leads to a corresponding decrease in the enzyme's operational steady-state affinity for O-2. This demonstrates directly that fast electron transfer between the haem groups is a key process in achieving the high affinity for oxygen in cell respiration. [References: 14]
机译：线粒体酶细胞色素c氧化酶催化真核细胞的呼吸作用。在细菌中，这种酶有许多变体，所有这些变体都有一个双核血红素铁-铜中心发生O-2还原，还有一个低自旋血红素，它是该中心的直接电子供体（1）。由于组织中溶解的O-2浓度低，细胞呼吸系统的组成部分对氧气具有高亲和力是至关重要的。然而，O-2与呼吸道血红铜氧化酶的结合非常弱（2,3）。这种悖论归因于在酶的双核血红素铁-铜中心结合的O-2的快速反应过程中的动力学捕获（2）。我们较早的工作（3）表明，从低自旋血红素到与氧结合的双核中心的电子转移对于这种动态氧捕获可能是必要的。在这里，我们显示出在来自大肠杆菌的呼吸血红素铜氧化酶中该血红素血红素电子转移速率的特定降低导致该酶对O-2的操作稳态亲和力相应降低。这直接表明，血红素基团之间的快速电子转移是实现细胞呼吸中对氧的高亲和力的关键过程。 [参考：14]

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