期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 54, 期 5, 页码 1512-1515出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201409881
关键词
charge transfer; enzyme catalysis; excited states; photochemistry; protochlorophyllide
资金
- UK Engineering and Physical Sciences Research Council [EP/J020192]
- Royal Society
- Engineering and Physical Sciences Research Council [EP/J020192/1] Funding Source: researchfish
- EPSRC [EP/J020192/1] Funding Source: UKRI
The unique light-driven enzyme protochlorophyllide oxidoreductase (POR) is an important model system for understanding how light energy can be harnessed to power enzyme reactions. The ultrafast photochemical processes, essential for capturing the excitation energy to drive the subsequent hydride-and proton-transfer chemistry, have so far proven difficult to detect. We have used a combination of time-resolved visible and IR spectroscopy, providing complete temporal resolution over the picosecond-microsecond time range, to propose a new mechanism for the photochemistry. Excited-state interactions between active site residues and a carboxyl group on the Pchlide molecule result in a polarized and highly reactive double bond. This so-called reactive intramolecular charge-transfer state creates an electron-deficient site across the double bond to trigger the subsequent nucleophilic attack of NADPH, by the negatively charged hydride from nicotinamide adenine dinucleotide phosphate. This work provides the crucial, missing link between excited-state processes and chemistry in POR. Moreover, it provides important insight into how light energy can be harnessed to drive enzyme catalysis with implications for the design of light-activated chemical and biological catalysts.
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