Document Detail


Excited-State Charge Separation in the Photochemical Mechanism of the Light-Driven Enzyme Protochlorophyllide Oxidoreductase.
MedLine Citation:
PMID:  25488797     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
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.
Authors:
Derren J Heyes; Samantha J O Hardman; Tobias M Hedison; Robin Hoeven; Greg M Greetham; Michael Towrie; Nigel S Scrutton
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-12-8
Journal Detail:
Title:  Angewandte Chemie (International ed. in English)     Volume:  -     ISSN:  1521-3773     ISO Abbreviation:  Angew. Chem. Int. Ed. Engl.     Publication Date:  2014 Dec 
Date Detail:
Created Date:  2014-12-9     Completed Date:  -     Revised Date:  2014-12-10    
Medline Journal Info:
Nlm Unique ID:  0370543     Medline TA:  Angew Chem Int Ed Engl     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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