Structure-function relationships of nickel-iron sites in hydrogenase and a comparison with the active sites of other nickel-iron enzymes

Recent studies of [NiFe]-hydrogenases have provided a significant amount of new structural and kinetic data on the many states the active site displays upon enzyme inhibition, its activation and during catalysis. Other Ni-Fe containing active sites have been found in the bifunctional carbon monoxide dehydrogenase/acetyl coenzyme A synthase that is involved in anaerobic carbon fixation through the Wood-Ljungdahl pathway. Here, we discuss the influence of the protein environment on the reactivity of these three active sites and analyze the differences and similarities in their structural and chemical properties.