Stepwise Hydride Transfer in a Biological System: Insights into the Reaction Mechanism of the Light-Dependent Protochlorophyllide Oxidoreductase
Stepwise Hydride Transfer in a Biological System: Insights into the Reaction Mechanism of the Light-Dependent Protochlorophyllide Oxidoreductase
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生物系统中的逐步氢化物转移：深入了解光依赖性原叶绿素内酯氧化还原酶的反应机制
DOI：
10.1002/ange.201712729
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发表时间：
2018
影响因子：
--
通讯作者：
Archipowa N
中科院分区：
文献类型：
--
作者：
Archipowa N
氢化物转移在许多生物系统中起着至关重要的作用。然而，其行动方式（协调一致或逐步）仍在争论中。光依赖性NADPH：原叶绿内酯氧化还原酶（POR）催化氢化物阴离子和质子在原叶绿内酯C17 - c18双键上的立体特异性反式加成。采用时间分辨吸收光谱和发射光谱研究了POR中氢化物的转移机理。除了原叶绿内酯的激发态外，还分解了三个离散的中间产物，与NADPH初始电子转移的逐步机制一致。随后的质子耦合电子转移和质子转移对野生型和C226S变体产生了截然不同的中间体，即初始氢化物附着在c17或C18上，但最终以相同的叶绿素内酯立体异构体结束。这项工作提供了生物系统中逐步氢化物转移的第一个证据。
Hydride transfer plays a crucial role in a wide range of biological systems. However, its mode of action (concerted or stepwise) is still under debate. Light‐dependent NADPH: protochlorophyllide oxidoreductase (POR) catalyzes the stereospecific trans addition of a hydride anion and a proton across the C17−C18double bond of protochlorophyllide. Time‐resolved absorption and emission spectroscopy were used to investigate the hydride transfer mechanism in POR. Apart from excited states of protochlorophyllide, three discrete intermediates were resolved, consistent with a stepwise mechanism that involves an initial electron transfer from NADPH. A subsequent proton‐coupled electron transfer followed by a proton transfer yield distinct different intermediates for wild type and the C226S variant, that is, initial hydride attaches to either C17or C18, but ends in the same chlorophyllide stereoisomer. This work provides the first evidence of a stepwise hydride transfer in a biological system.