Functioning of a key photoenzyme decrypted

The functioning of the FAP enzyme, useful for producing biofuels and green chemistry, has been deciphered. This result mobilized an international team of scientists, including many French researchers from CEA, CNRS, Inserm, École Polytechnique, the universities of Grenoble Alpes, Paris-Saclay and Aix-Marseille, as well as the European Synchrotron and the Synchrotron SOLEIL. This discovery is published in Science on 09/04/2021.
The functioning of the FAP enzyme, useful for producing biofuels and green chemistry, has been deciphered. This result mobilized an international team of scientists, including many French researchers from CEA, CNRS, Inserm, École Polytechnique, the universities of Grenoble Alpes, Paris-Saclay and Aix-Marseille, as well as the European Synchrotron and the Synchrotron SOLEIL. This discovery is published in Science on 09/04/2021.

Understanding the functioning of PAF is essential because this photoenzyme represents a new opportunity for the sustainable production of biofuels from fatty acids naturally produced by living organisms. PAF is also very promising for the production of high value-added compounds for fine chemicals, cosmetics or pharmaceuticals. Finally, due to the fact that their reaction is triggered by light, photoenzymes give access to ultra-fast phenomena taking place during enzymatic reactions. Thus, PAF also represented a unique opportunity to understand in detail a chemical reaction taking place in living organisms.
More precisely, in this work, the researchers show that when the PAF is illuminated and absorbs a photon, an electron is torn off in 300 picoseconds from the fatty acid produced by the algae. This fatty acid is then dissociated into hydrocarbon precursor and carbon dioxide (CO2). Most of the latter is then converted to bicarbonate (HCO3-) in 100 nanoseconds. This activity uses light, but does not prevent photosynthesis: the flavin molecule embedded in the PAF, which absorbs the photon, is bent. This conformation shifts the absorption spectrum of the molecule towards the red, so that it uses photons not exploited for the photosynthetic activity of the microalgae.

 

Plus précisément, dans ce travail, les chercheurs montrent que lorsque la FAP est éclairée et absorbe un photon, un électron est arraché en 300 picosecondes à l’acide gras produit par les algues. Cet acide gras est alors dissocié en précurseur d’hydrocarbure et en dioxyde de carbone (CO2). La majorité de ce dernier est ensuite transformée en bicarbonate (HCO3-) en 100 nanosecondes. Cette activité utilise de la lumière, mais n’empêche pas la photosynthèse : la molécule de flavine intégrée à la FAP, qui absorbe le photon, est courbée. Cette conformation déplace le spectre d’absorption de la molécule vers le rouge, de sorte qu’elle utilise des photons non exploités pour l’activité photosynthétique de la microalgue.

It is the combined interpretation of the results of various experimental and theoretical approaches by the international consortium that provides a detailed atomic-scale picture of the PAF at work. The multidisciplinary study combined work in bioengineering, optical and vibrational spectroscopy, static and kinetic crystallography performed with synchrotrons or an X-ray free electron laser, as well as quantum chemical calculations.

In France1, this study mobilized researchers from the Aix-Marseille Biosciences and Biotechnology Institute (CEA/CNRS/Aix-Marseille University), the Structural Biology Institute (CEA/CNRS/Grenoble Alpes University), the Optics and Biosciences Laboratory (CNRS/Paris Polytechnic Institute/Inserm) the Advanced Spectroscopy Laboratory for Interactions, Reactivity and the Environment (CNRS/University of Lille), the Institute for Integrative Cell Biology (CEA/CNRS/University of Paris-Saclay), the SOLEIL synchrotron, as well as the European Synchrotron (ESRF) and the Institut Laue Langevin (ILL), two large European instruments located in Grenoble. It was funded by the French National Research Agency.