Stepwise Hydride Transfer in a Biological System: Insights into the Reaction Mechanism of the Light-Dependent Protochlorophyllide Oxidoreductase.

Nataliya Archipowa, Roger J Kutta, Derren J Heyes, Nigel S Scrutton

Angewandte Chemie (International ed. in English) 2018 Mar 01

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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 -C18 double 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 C17 or C18 , but ends in the same chlorophyllide stereoisomer. This work provides the first evidence of a stepwise hydride transfer in a biological system. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Citation

Nataliya Archipowa, Roger J Kutta, Derren J Heyes, Nigel S Scrutton. Stepwise Hydride Transfer in a Biological System: Insights into the Reaction Mechanism of the Light-Dependent Protochlorophyllide Oxidoreductase. Angewandte Chemie (International ed. in English). 2018 Mar 01;57(10):2682-2686