Heyes Derren J, Hardman Samantha J O, Mansell David, Ní Cheallaigh Aisling, Gardiner John M, Johannissen Linus O, Greetham Gregory M, Towrie Michael, Scrutton Nigel S
Manchester Institute of Biotechnology and School of Chemistry, The University of Manchester , 131 Princess Street, Manchester M1 7DN, U.K.
Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council , Harwell Oxford, Didcot OX11 0QX, U.K.
J Phys Chem B. 2017 Feb 16;121(6):1312-1320. doi: 10.1021/acs.jpcb.7b00528. Epub 2017 Feb 7.
Protochlorophyllide (Pchlide), an intermediate in the biosynthesis of chlorophyll, is the substrate for the light-driven enzyme protochlorophyllide oxidoreductase. Pchlide has excited-state properties that allow it to initiate photochemistry in the enzyme active site, which involves reduction of Pchlide by sequential hydride and proton transfer. The basis of this photochemical behavior has been investigated here using a combination of time-resolved spectroscopies and density functional theory calculations of a number of Pchlide analogues with modifications to various substituent groups. A keto group on ring E is essential for excited-state charge separation in the molecule, which is the driving force for the photoreactivity of the pigment. Vibrational "fingerprints" of specific regions of the Pchlide chromophore have been assigned, allowing identification of the modes that are crucial for excited-state chemistry in the enzyme. This work provides an understanding of the structural determinants of Pchlide that are important for harnessing light energy.
原叶绿素酸酯（Pchlide）是叶绿素生物合成过程中的一种中间体，是光驱动酶原叶绿素酸酯氧化还原酶的底物。Pchlide具有激发态特性，使其能够在酶活性位点引发光化学反应，该反应涉及通过连续的氢化物和质子转移对Pchlide进行还原。本文结合时间分辨光谱学和对多个对不同取代基进行修饰的Pchlide类似物的密度泛函理论计算，对这种光化学行为的基础进行了研究。E环上的酮基对于分子中的激发态电荷分离至关重要，而电荷分离是该色素光反应性的驱动力。已确定了Pchlide发色团特定区域的振动“指纹”，从而能够识别对酶中激发态化学至关重要的模式。这项工作有助于理解Pchlide中对于利用光能很重要的结构决定因素。
