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NiFe Hydrogenase
() hydrogenase is a type of hydrogenase, which is an oxidative enzyme that reversibly activates molecular hydrogen in prokaryotes and some eukaryotes. The catalytic site on the enzyme provides simple hydrogen-metabolizing microorganisms a redox mechanism by which to store and utilize energy via the reaction shown in Figure 1. This is particularly essential for the anaerobic, sulfate-reducing bacteria of the genus ''Desulfovibrio''. The practical application of this enzyme is a renewable, more environmentally friendly energy source.
==Structure==
The structure of () hydrogenase was obtained from x-ray crystallography studies of five different sulfate-reducing bacteria: ''D. vulgaris'' Miyazaki F, ''D. gigas'', ''D. frutosovorans'', ''D. desulfuricans'' and ''Desulfomicrobium baculatum''. The () hydrogenase isolated from ''D. vulgaris'' Miyazaki F is shown in Figure 2. The larger subunit is in blue, has a molecular mass of 62.5 kDa, and houses the Ni-Fe active site. The smaller subunit is in magenta, has a molecular mass of 28.8 kDa, and contains the Fe-S clusters (see Iron-sulfur cluster).
From the infrared spectra and X-ray crystallography studies, the () hydrogenase active site was found to be (S-Cys)4Ni(μ-X)Fe(CO)(CN)2, in which the generic ligand X is either an oxide, sulfur, hydroperoxide, or a hydroxide found in an oxidized state only (Figure 3). While the nickel atom participates in redox reactions, the iron atom is consistently in a Fe(II) coordination state.〔 The exact geometry of the three non-protein ligands (denoted as L) coordinating to the Fe metal ion is not known; however, they were identified as one carbon monoxide (C≡O) molecule and two cyanide (−C≡N) molecules.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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