How algae produce hydrogen—news from the photosynthetic hydrogenase

Green algae are the only known eukaryotes capable of oxygenic photosynthesis which are equipped with a hydrogen metabolism. Hydrogen production is light-dependent, since the [FeFe] hydrogenases are coupled to the photosynthetic electron transport chain via ferredoxin. Algal [FeFe] hydrogenases are one of the most active biocatalysts for the evolution of hydrogen. Therefore, special interest exists in the biophysical characterization and biotechnological usage of these [Fe-S] enzymes. This review traces the discovery of this interesting class of proteins. Recent findings allow insight into the electronic structure and configuration of the [FeFe] hydrogenase active site (H-cluster). Emphasis is placed on novel discoveries of the hydrogenase interaction with its natural electron donor ferredoxin and the mechanism of enzyme inactivation through oxygen.