Role of Fe-hydrogenase in biological hydrogen production

Fe-hydrogenase is a distinct class of hydrogen-producing metalloenzyme, present in a wide variety of pro. karyotes and eukaryotes. It functions either in the utilization of hydrogen as a growth substrate (H-2 uptake) or in the disposing of excess electrons by combining them with protons to form hydrogen (H2 evolution). The reversible conversion of molecular hydrogen (H-2) to protons (H+) and electrons is a central reaction in the biological energy cycle of all hydrogen-producing organisms. The active centre of the Fe-hydrogenases contains a unique bimetallic (Fe-Fe) centre with non-protein ligands (CO, CN). X-ray crystallography and spectroscopic studies reveal that Fe-hydrogenase is a simpler system than the Ni-Fe counterpart. The present work summarizes the role of Fe-hydrogenase in the microbial production of hydrogen. Classification, distribution and localization of Fe-hydrogenase enzymes and their structural diversity have also been highlighted.