A Minimal Light‐Driven System to Study the Enzymatic CO 2 Reduction of Formate Dehydrogenase

A minimal light‐driven approach was established for studying enzymatic CO 2 conversion spectroscopically. The system consists of a photosensitizer Eosin Y, EDTA as a sacrificial electron donor and substrate source, and formate dehydrogenase from Rhodobacter capsulatus ( Rc FDH) as a biocatalyst. This simplified three‐component system provides a photo‐triggered control for in situ characterization of the entire catalytic reaction. Direct reduction of Rc FDH by the photosensitizer without additional electron carriers was confirmed via UV‐Vis spectroscopy, while GC‐MS and IR spectroscopy were used to follow photoinduced CO 2 generation from EDTA and its subsequent enzymatic reduction, yielding the product formate. Photo‐driven and in vitro , dye‐based CO 2 reduction was inhibited by azide under a mixed (competitive‐non‐competitive) inhibition mode. IR spectroscopy reveals displacement of the competitively‐bound azide by CO 2 , reflecting an interaction of both with the active site cofactor. This work comprises a proof‐of‐concept for a new approach to employ light for regulating the reaction of formate dehydrogenases and other CO 2 reductases.