Excited state dynamics and catalytic mechanism of the light-driven enzyme protochlorophyllide oxidoreductase
Excited state dynamics and catalytic mechanism of the light-driven enzyme protochlorophyllide oxidoreductase
复制标题
DOI：
10.1039/c2cp23789j
复制
发表时间：
2012-01-01
影响因子：
3.3
通讯作者：
Heyes, Derren J.
中科院分区：
文献类型：
--
作者：
Scrutton, Nigel S.;Groot, Marie Louise;Heyes, Derren J.
原叶绿素内酯 (Pchlide) 在原叶绿素内酯氧化还原酶 (POR) 的催化下还原为叶绿素内酯，是叶绿素生物合成途径的倒数第二步，也是关键的光驱动反应，可引发植物发育的深刻转变。由于 POR 是光激活的，因此它可以提供有关如何利用光能为酶反应提供动力的新信息。因此，POR 提供了一个独特的机会来研究低温和超快时间尺度的催化作用，而这对于大多数酶来说通常是无法实现的。我们对 POR 催化机制理解的最新进展说明了为什么它是研究酶催化和反应动力学的重要模型。该反应涉及一种氢化物和一种质子的加成，并且通过 Pchlide 底物吸收光来引发催化作用。由于反应涉及 Pchlide 激发态，各种超快光谱测量表明反应的重要部分发生在皮秒时间尺度上。一些激发态 Pchlide 物种，包括分子内电荷转移络合物和氢键中间体，被认为是随后发生在微秒时间尺度上的氢化物和质子转移所必需的。在此，我们回顾了光谱研究，特别关注用于研究 POR 激发态动力学和催化机制的时间分辨瞬态吸收和荧光实验。
The reduction of protochlorophyllide (Pchlide) to chlorophyllide, catalysed by the enzyme protochlorophyllide oxidoreductase (POR), is the penultimate step in the chlorophyll biosynthetic pathway and is a key light-driven reaction that triggers a profound transformation in plant development. As POR is light-activated it can provide new information on the way in which light energy can be harnessed to power enzyme reactions. Consequently, POR presents a unique opportunity to study catalysis at low temperatures and on ultrafast timescales, which are not usually accessible for the majority of enzymes. Recent advances in our understanding of the catalytic mechanism of POR illustrate why it is an important model for studying enzyme catalysis and reaction dynamics. The reaction involves the addition of one hydride and one proton, and catalysis is initiated by the absorption of light by the Pchlide substrate. As the reaction involves the Pchlide excited state, a variety of ultrafast spectroscopic measurements have shown that significant parts of the reaction occur on the picosecond timescale. A number of excited state Pchlide species, including an intramolecular charge transfer complex and a hydrogen bonded intermediate, are proposed to be required for the subsequent hydride and proton transfers, which occur on the microsecond timescale. Herein, we review spectroscopic investigations, with a particular focus on time-resolved transient absorption and fluorescence experiments that have been used to study the excited state dynamics and catalytic mechanism of POR.