Sunlight-Dependent Hydrogen Production by Photosensitizer/Hydrogenase Systems

We report a sustainable in vitro system for enzyme-based photohydrogen production. The [FeFe]-hydrogenase HydA1 from Chlamydomonas reinhardtii was tested for photohydrogen production as a proton-reducing catalyst in combination with eight different photosensitizers. Using the organic dye 5-car-boxyeosin as a photosensitizer and plant-type ferredoxin PetF as an electron mediator, HydA1 achieves the highest light-driven turnover number (TONHydA1) yet reported for an enzyme-based in vitro system (2.9 x 10(6) mol(H-2) mol(cat)(-1)) and a maximum turnover frequency (TOFHydA1) of 550 mol(H-2) mol(HydA1)(-1) s(-1). The system is fueled very effectively by ambient daylight and can be further simplified by using 5-carboxyeosin and HydA1 as a two-component photosensitizer/ biocatalyst system without an additional redox mediator.