[NiFe] and [FeFe] hydrogenases studied by advanced magnetic resonance techniques

Hydrogenase is a enzyme that can be found in many microorganisms such as bacteria and archae to eukarya as well as in specialized cellular compartments. It is classified into [NiFe], [FeFe] and [Fe]. The first two hydrogenases contains sulfur-bridge metallic centers, commonly with an open coordination site on one metal. The first hydrogenase are often more active in H2 oxidation while the second, in the production of molecular hydrogen. In 1987, [NiFe] was first crystallized and presently, structures from five [NiFe] hydrogenases from closely related sulfated-reducing bacteria are known such as Desulfovibrio (D.) gigas, D. vulgaris Miyazaki F, D. desulfuricans, D. fructosovorans and Desulfomicrobium (Dm.) baculatum. The different states of the enzymes and some mutant of D. fructosovorans, structures were obtained. In [FeFe] hydrogeanses, three enzymes have been characterized which are Megasphaera (M.) elsdenii, Desulfovibrio (D.) vulgaris Hildenborough and D. desulfuricans and all these contain 14 Fe atoms per protein molecule arranged in three Fe-S clusters that includes H-cluster. In identification and structural characterization of these enzymes, the electron paramagnetic resonance (EPR) plays an important role because [NiFe] and [FeFe] occur in these paramagnetic metal sites. Using the combination of spectroscopic and theoretical methods provides a fruitful hydrogenase research obtaining reliable structures of reaction intermediates.