Challenge of new biological energy resources

Hydrogenases are enzymes that can reversibly split molecular hydrogen. Study on the structure of the active site and the mechanism of catalysis has drawn great attention because the results may be useful for the design of cheap biomimetic hydrogen catalysts for fuel cells, or as model for the photoproduction of H₂. At one time the active site was generally considered to be composed of mononuclear nickel complex with ligands from the polypeptide. A breakthrough in the understanding of the structure of NiFe] Hases occurred with the resolution crystal structure ofD. gigas NiFe] Hases in 1995. The unexpected result challenged the previously reported spectroscopic studies and caused some academic arguments. Some methods and results used for insight into NiFe] Hases have to be reconsidered. Different viewpoints concerning the structure of active site of NiFe] Hases in different periods and some remaining questions will be presented.