NiFeS enzymes

The structures of all three types of enzyme have been recently resolved 417-421 The first was the structure of the [NiFe] enzyme from Desulfovibrio gigas422 which revealed an active site containing a Ni center coordinated by 7-S of a cysteine (Cys 530) in an apical position and by three... 

The active site of the NiFe enzyme is 30 from the surface. Volbeda et al. proposed a proton transfer chain beginning at the NiFe cluster to His72 to His 536 through two water molecules finally to Glu46 at the surface. All of these residues are highly conserved among the NiFe hydrogenases. Two other histidine residues were also considered to have a possible role in proton transfer. 

Keywords Acet)d coenzyme A synthase Carbon monoxide dehydrogenase Geochemical theory of the origin of life Hydrogenase NiFeS-enzymes... 

The nickel of the [NiFe] enzyme has an EPR active, odd-electron oxidized Ni(III) form but can be reduced to an EPR inactive Ni(II) form, and then to a more reduced, odd-electron Ni(l) form an even more reduced even-electron form is also known. ... 

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