Nickel hydrogenase

Canaguier S, Artero V, Fontecave M. Modelling NiFe hydrogenases nickel-based electrocatalysts for hydrogen production. Dalton Trans. 2008 (3) 315-25. 

This trace element is in combination with iron and selenium in the hydrogenase mentioned previously in the sections on iron and selenium, which is known to be active in oxidation-reduction reactions (giving or taking electrons), an important activity of a class of enzymes. Nickel also has a role in the regulation of hydrogenases. Nickel binds easily to amino acids and to proteins such as globulins (which can be turned into transporters of metals in the bloodstream). Nickel proteins may be used to stabilize certain molecules. 

Methanobacterium formicicum formate dehydrogenases, 663 Methanobacterium thermoautotrophicum hydrogenases nickel, 647... 

Frenking G, Cremer D (1990) The Chemistry of the Nobles Gas Elements Helium, Neon, and Argon - Experimental Facts and Theoretical Predictions. 73 17-96 Frey M (1998) Nickel-Iron Hydrogenases Structural and Functional Properties. 90 97-126 Fricke B (1975) Superheavy Elements. 21 89-144... 

NICKEL-IRON-SULFUR ACTIVE SITES HYDROGENASE AND CO DEHYDROGENASE... 

In contrast to the abundance of Fe-proteins, there are only six known nickel-containing enzymes hydrogenase, CO dehydrogenase (CODA), acetyl-CoA synthase (ACS), superoxide dismutase, urease, and S-methyl-CoM methylreductase. Among these enzymes, it exists in very diverse environments, including a dinickel site (urease), a Ni-Fe heterobinuclear site (hydrogenase), a Ni-Fe4S4 heterometallic... 

Maier, T. Bock, A. Nickel Incorporation into Hydrogenases VCH Publishers New York, 1996. 

The hydrogenases isolated can be broadly classified into two groups [Fe-S]-only, and nickel-[Fe-S]-containing hydrogenases. The first group, the [Fe-S]-only or [Fe] hydrogenases, is characterized by the absence of nickel on the active site, and are rare in sulfate reducing bacteria. They contain [4Fe-4S] clusters and, in addition, a catalytic... 

The [NiFe] hydrogenase from D. gigas has been used as a prototype of the [NiFe] hydrogenases. The enzyme is a heterodimer (62 and 26 kDa subunits) and contains four redox active centers one nickel site, one [3Fe-4S], and two [4Fe-4S] clusters, as proven by electron paramagnetic resonance (EPR) and Mosshauer spectroscopic studies (174). The enzyme has been isolated with different isotopic enrichments [6 Ni (I = I), = Ni (I = 0), Fe (I = 0), and Fe (I = )] and studied after reaction with H and D. Isotopic substitutions are valuable tools for spectroscopic assignments and catalytic studies (165, 166, 175). 

Most of the as-isolated [NiFe] hydrogenases are inactive, and the nickel center exhibits an intense rhombic EPR signal termed Ni-A (g = 2.31, 2.26, and 2.02) with variable amounts of a second nickel species, named Ni-B (g = 2.33, 2.16, and 2.02), with slightly different... 

Fe Q-band ENDOR study of the isotopically enriched Ni-C state of D. gigas and D. desulfuricans hydrogenases and Ni-B state of D. desulfuricans revealed a weak coupling between the Fe and the nickel atoms when the enzyme was in the Ni-A forms while no coupling was observed for the Ni-B form (186). A careful analysis of linewidth of Ni-A and Ni-B EPR signals detected in Fe enriched and nonenriched hydrogenase samples indicated that hyperfine interactions are lost in the spectral linewidth and, hence, nonde-tectable. 

De Luca G, P de Philip, Z Dermoun, M Rouseet, A Vermeglio (2001) Reduction of Technetium (VII) by Desulfovibrio fructosovorans is mediated by the nickel-iron hydrogenase. Appl Environ Microbiol 67 468-475. 

Wang C-P, R Franco, JJG Moura, 1 Moura, EP Day (1992) The nickel site in active Desulfovibrio baculatus [NiFeS] hydrogenase is diamagnetic. Multifield saturation magnetization measurement of the spin state of Ni(II). 7 Sio/ Chem 267 7378-7380. 

The first Ni Mossbauer spectrum of nickel in a bioinorganic compound with determinable EFG and isomer shift was reported for a nickel complex compound with planar [NiSJ core and considered as a model compound for hydrogenase. This Mossbauer spectrum from the formal Ni compound is presented in Fig. 7.16. The observed quadrupolar interaction can be understood in terms of ligand field theory. In this approach, the b g and levels (d y2 and d ) are not occupied which is expected to cause a large negative EFG contribution [32]. 

Fig. 7.16 Ni Mossbauer spectrum at 4.2 K of a nickel complex compound with planar [NiS4] core known as a model compound for hydrogenase (source Nio.gsCro.is (97% enriched) activated at Mainz Microtron) (from [32])...

Amara, P., Volbeda, A., Fontecilla-Camps, J. C., Field, M. J., 1999, A Hybrid Density Functional Theory/Mo-lecular Mechanics Study of Nickel-Iron Hydrogenase Investigation of the Active Site Redox States , J. Am. Chem. Soc., 121, 4468. 

Nickel is found in thiolate/sulflde environment in the [NiFe]-hydrogenases and in CODH/ACS.33 In addition, either a mononuclear Ni-thiolate site or a dinuclear cysteine-S bridged structure are assumed plausible for the new class of Ni-containing superoxide dismutases, NiSOD (A).34 [NiFe]-hydrogenase catalyzes the two-electron redox chemistry of dihydrogen. Several crystal structures of [NiFe]-hydrogenases have demonstrated that the active site of the enzyme consists of a heterodinuclear Ni—Fe unit bound to thiolate sulfurs of cysteine residues with a Ni—Fe distance below 3 A (4) 35-39 This heterodinuclear active site has been the target of extensive model studies, which are summarized in Section 6.3.4.12.5. 

Nickel-selenium coordination compounds have received attention in recent years, because a unique Ni-selenocysteine interaction was revealed in the active site of [FeNiSe]-hydrogenases.1083,1084 Of particular interest in this regard are mixed CO/selenolate complexes. Distorted square planar (393) was prepared from [CpNi(CO)]2, PhSeSePh, and [Fe(CO)3(SePh)3] and provides the first example of CO bound to a square planar Ni11 center in thiolate/selenolate environment.1085,1086 Upon addition of RSSR, species of the series [Ni(CO)(SR) (SePh)3 ] are formed. //(CO) ranges from 2,023 cm-1 to 2,043 cm-1 and is regarded as a spectroscopic reference for the CO binding site in [NiFeSe] hydrogenases. 

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