Biological activition of hydrogen

Happe, Randolph P.; Roseboom, Winfried; Pierik, Antonio J.; Albracht, S.P.J.; Bagley, Kimberly A.

doi:10.1038/385126a0

Cited by 441 publications

(381 citation statements)

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“…One possibility would be that the redox chemistry takes place at another redox component. In view of the knowledge that the active site is composed of a dinuclear cluster of iron and nickel [27,28,31, 321 it is conceivable that the iron undergoes most of the redox changes, as is suggested by the frequency shift of the v(CN) and v(C0) stretch vibrations [31]. Via spin-spin coupling this could make the unpaired spin of the nickel either EPR detectable if the iron ion is diamagnetic, or undetectable if the iron ion is paramagnetic (in the S = 1/2 state).…”

Section: Discussionmentioning

confidence: 99%

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Changes in the Electronic Structure Around Ni in Oxidized and Reduced Selenium‐Containing Hydrogenases from Methanococcus Voltae

Sorgenfrei

Duin

Klein

et al. 1997

European Journal of Biochemistry

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The selenium-containing F420-reducing hydrogenase from Methanococcus voltae was anaerobically purified to a specific hydrogen-uptake activity of 350 U/mg protein as determined with the natural electron acceptor. The concentrated enzyme was used for EPR-spectroscopic investigations. As isolated, the enzyme showed an EPR spectrum with gnyL values of 2.21, 2.15 and 2.01. Illumination of such samples at low temperatures led to an EPR spectrum with gxyz values of 2.05, 2.11 and 2.29. These spectra are typical for [NiFeIhydrogenases in the active state. Spectra of samples enriched in 77Se showed a hyperfine interaction between the unpaired spin of the nickel ion and the nuclear spin of one "Se atom before and after illumination. A 90" flip of the electronic z-axis is proposed to explain the hyperfine interaction in both states. This has been demonstrated previously only for the F420-non-reducing hydrogenase from M . voltue, where the selenium atom is present as a selenocysteine residue on an unusuallyThe results demonstrate that the three-dimensional structures of the active sites in the selenium-containing F420-reducing and F420-non-reducing hydrogenases from M. voltue are highly similar and hence are not influenced by the unusual subunit structure of the latter enzyme. Oxidized samples containing either natural selenium or 77Se were prepared from the F420-reducing and the selenium-containing F420-nonreducing hydrogenase. Both enzymes exhibited EPR spectra typical for [NiFeIhydrogenases in the inactive 'ready' state. In contrast to the reduced form, no splitting of the nickel-derived signal due to the nuclear spin of "Se was observed in the oxidized state, indicating that the electronic z-axis is perpendicular to the Ni-Se direction.Keywords: [NiFeIhydrogenase ; EPR ; purification ; selenium ; selenocysteine.The simplest biochemical redox reaction, namely the reversible, heterolytic cleavage of dihydrogen into two protons and two electrons is catalysed by enzymes called hydrogenases [I, 21. These are found in many organisms from all three domains, bacteria, eukarya and archaea. Different classes are defined according to the metal content of the enzymes. One class comprises hydrogenases containing no metal other than iron. These enzymes are called Fe-only hydrogenases or [Felhydrogenases [l]. The second class consists of hydrogenases that contain nickel in addition to iron. Accordingly these enzymes were named [NiFeIhydrogenases. Most of the characterized hydrogenases belong to this group. The EPR spectra of nickel respond to redox changes [4-71 and this M. voltae is an anaerobic archaeon that gains energy by oxidation of hydrogen via hydrogenases and concomitant reduction Correspondence to 0. Sorgenfrei,

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Section: Discussionmentioning

confidence: 99%

“…The Fe ion is low spin and has an octahedral coordination with 5-6 ligands: Two cysteine thiols and an oxygen atom [28, 321, bridg-ing between iron and nickel, plus two CN-and one CO molecules [31]. The nickel ion has five ligands in an octahedral coordination : three bridging ligands described above and two thiols [28,321.…”

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confidence: 99%

Changes in the Electronic Structure Around Ni in Oxidized and Reduced Selenium‐Containing Hydrogenases from Methanococcus Voltae

Sorgenfrei

Duin

Klein

et al. 1997

European Journal of Biochemistry

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“…However, intricate molecular constructions with exogeneous redox active centres attached to the diiron unit that mimic the structure of the full H-cluster suffer from instability and low activity 8 . Full catalytic activity for proton reduction approaching the efficiency of the enzyme has only been achieved in hybrid constructs where the synthetic model (m-(SCH 2 ) 2 NH)[Fe(CO) 2 (CN)] 2 2 À has been inserted into the apo-[FeFe]-H 2 ase protein 9,10 . If the substantive goal of creating robust electrocatalysts in simple to assemble, earth-abundant materials is to be realized, we posit that a broader search for metal/ligand frameworks is needed.…”

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Redox active iron nitrosyl units in proton reduction electrocatalysis

et al. 2014

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Base metal, molecular catalysts for the fundamental process of conversion of protons and electrons to dihydrogen, remain a substantial synthetic goal related to a sustainable energy future. Here we report a diiron complex with bridging thiolates in the butterfly shape of the 2Fe2S core of the [FeFe]-hydrogenase active site but with nitrosyl rather than carbonyl or cyanide ligands. This binuclear [(NO)Fe(N 2 S 2 )Fe(NO) 2 ] þ complex maintains structural integrity in two redox levels; it consists of a (N 2 S 2 )Fe(NO) complex (N 2 S 2 ¼ N,N 0 -bis(2-mercaptoethyl)-1,4-diazacycloheptane) that serves as redox active metallodithiolato bidentate ligand to a redox active dinitrosyl iron unit, Fe(NO) 2 . Experimental and theoretical methods demonstrate the accommodation of redox levels in both components of the complex, each involving electronically versatile nitrosyl ligands. An interplay of orbital mixing between the Fe(NO) and Fe(NO) 2 sites and within the iron nitrosyl bonds in each moiety is revealed, accounting for the interactions that facilitate electron uptake, storage and proton reduction.

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“…The bimetallic NiFe center is deeply buried in the large subunit; it is coordinated to the protein by four cysteines. Further studies using infrared spectroscopy revealed the presence of three non-protein ligands, 1 CO and 2 CN -, bound to the Fe atom (Volbeda et al, 1996;Happe et al, 1997). The small subunit contains up to three Fe-S clusters which conduct electrons between the H 2 -activating center and the physiological electron acceptor (or donor) of H 2 ase.…”

Section: The [Nife]-h 2 Asesmentioning

confidence: 99%

“…In the aerobically isolated inactive form of the enzyme, there is an additional µ-oxo or hydroxo (Garcin et al, 1999;Volbeda et al, 2002) or sulfi do group (Higuchi et al, 1997;Matias et al, 2001) bridging the Ni and Fe atoms. In addition, as demonstrated by crystallography and spectroscopy, the iron atom is bound to non-protein diatomic ligands, normally poisonous molecules, two CN -and one CO (Volbeda et al, 1996;Happe et al, 1997;Pierik et al, 1999), or SO, CO and CN -in D. vulgaris (Higuchi et al, 1997(Higuchi et al, , 2000. The FTIR and EPR properties of the metallocenter of the cytoplasmic NAD-reducing H 2 ase of R. eutropha (SH) suggested the presence of two additional CN -ligands, so that SH may have a Ni(CN)Fe(CN) 3 (CO) at its active site (Happe R.P.…”

Section: Active Sites and Model Compoundsmentioning

confidence: 99%

Molecular Biology of Microbial Hydrogenases

2004

Current Issues in Molecular Biology

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Biological activition of hydrogen

Cited by 441 publications

References 9 publications

Changes in the Electronic Structure Around Ni in Oxidized and Reduced Selenium‐Containing Hydrogenases from Methanococcus Voltae

Changes in the Electronic Structure Around Ni in Oxidized and Reduced Selenium‐Containing Hydrogenases from Methanococcus Voltae

Redox active iron nitrosyl units in proton reduction electrocatalysis

Molecular Biology of Microbial Hydrogenases

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