Hydrogen‐Activating Enzymes: Activity Does Not Correlate with Oxygen Sensitivity

Baffert, Carole; Demuez, Marie; Cournac, Laurent; Burlat, Bénédicte; Guigliarelli, Bruno; Bertrand, Patrick; Girbal, Laurence; Léger, Christophe

doi:10.1002/anie.200704313

Cited by 82 publications

(137 citation statements)

References 9 publications

(1 reference statement)

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“…Its apparent time constant of ϳ4 s is the upper limit, because it was largely based on HydA1 samples containing mostly substoichiometric O 2 concentrations. Slower inhibition of [FeFe]-H 2 ases at lower O 2 levels as well was observed in electrochemical studies (6,38). However, also for HydA1 in a nearly stoichiometric protein/O 2 mixture, surplus Fe-C,O bonds were detected already after the shortest O 2 exposure.…”

Section: Discussionsupporting

confidence: 62%

“…In electrochemical experiments, a time constant of ϳ10 s for O 2 -induced inactivation of HydA1 at 10°C was found (6), which is smaller than that of the 15-s phase. Two phases during O 2 inhibition, the slower one being irreversible, were also described for the [FeFe]-H 2 ase of C. acetobutylicum (38). Accordingly, the 15-s phase in HydA1 presumably is associated with the inactivation of H 2 conversion due to irreversible modifications at the [4Fe4S] cluster.…”

Section: Discussionmentioning

confidence: 81%

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O2 Reactions at the Six-iron Active Site (H-cluster) in [FeFe]-Hydrogenase

Lambertz

Leidel

Havelius

et al. 2011

Journal of Biological Chemistry

144

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[FeFe]-hydrogenase (H 2 ase) 4 proteins are the most active biological catalysts for the production of molecular hydrogen (H 2 ) from proton reduction, with reported turnover rates of up to 10 4 s Ϫ1 (1, 2). Therefore, these enzymes are of high interest for biotechnology, aiming at the generation of H 2 as a renewable fuel (1, 3-5). However, a severe limitation for such applications is the rapid inactivation of [FeFe]-H 2 ases by dioxygen (O 2 ) (6, 7). Understanding the mechanism of O 2 -induced inactivation may allow the improvement of enzyme features to yield increased O 2 tolerance (e.g. by genetic engineering, which has already been demonstrated for NiFe hydrogenases) (8 -10).[FeFe]-H 2 ases are found in certain bacteria and green algae (11, 12). All of these enzymes contain an active site that consists of an inorganic iron complex, which is denoted as the H-cluster (13-15). The [FeFe]-H 2 ase enzymes from anaerobic bacteria in addition bind several iron-sulfur (FeS) clusters, serving as a relay for electron transfer to and from the active site (13-15).[FeFe]-H 2 ases from green algae represent the minimal unit for biological H 2 production because they contain only the H-cluster, whereas accessory FeS clusters are absent (16). This feature renders these enzymes most suitable for spectroscopic investigations on O 2 -induced inactivation (17), focusing on the active site reactions. The general structure of the H-cluster has been unraveled by crystallography, x-ray absorption spectroscopy (XAS), EPR, and FTIR spectroscopy on H 2 ase protein from various organisms (18). The H-cluster structure in both bacteria and green algae appears to be similar overall (16,19,20). It features a [4Fe4S] cubane cluster, which is bound by four cysteine residues to the protein and is linked by one of them to a binuclear iron unit (2Fe H ) (Fig. 1). The latter carries two cyanide (CN Ϫ ) ligands and three carbon monoxide (CO) ligands (21, 22) and presumably an azadithiolate group (adt; (SCH 2 ) 2 NH) in the metal-bridging position (21,23,24). Both types of diatomic ligands are probably derived from a biosynthetic pathway starting with tyrosine (25-27). The nitrogen atom of the adt has been proposed to be involved in proton transfer at the active site (21, 28). The H-cluster structure is assembled in a complex reaction involving three maturation proteins (29 -34). H 2 formation has been proposed to involve the binding and reduction of a single proton, which transiently creates a hydride ligand, either located in a bridging position between the two iron ions or terminally bound at the distal iron ion of the 2Fe H moiety (Fig. 1). After a second protonation step, H 2 is released from the H-cluster (35)(36)(37) 4 The abbreviations used are: H 2 ase, hydrogenase; adt, azadithiolate; EXAFS, extended x-ray absorption fine structure; NaDT, sodium dithionite; ROS, reactive oxygen species; XANES, x-ray absorption near edge structure; XAS, x-ray absorption spectroscopy; FT, Fourier transform.

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Section: Discussionsupporting

confidence: 62%

Section: Discussionmentioning

confidence: 81%

O2 Reactions at the Six-iron Active Site (H-cluster) in [FeFe]-Hydrogenase

Lambertz

Leidel

Havelius

et al. 2011

Journal of Biological Chemistry

144

View full text Add to dashboard Cite

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“…The modification of an electrode by hydro- genase reduces the overpotential to a value close to zero and allows hydrogen production at a higher potential than on a platinum surface. This has been shown for a variety of hydrogenase enzymes including the [NiFe]-hydrogenases of Ralstonia species on a rotating disk graphite electrode (Goldet et al, 2008) and the [FeFe]-hydrogenases of Desulfovibrio desulfuricans (Vincent et al, 2005) and Clostridium acetobutylicum (Baffert et al, 2008). As an advantage, [FeFe]-hydrogenases have a higher hydrogen production activity (Adams, 1990;Peters et al, 1998;Nicolet et al, 1999) compared to [NiFe]-hydrogenases and suffer less of product inhibition (Léger et al, 2004).…”

Section: Introductionmentioning

confidence: 93%

Immobilization of the [FeFe]-hydrogenase CrHydA1 on a gold electrode: Design of a catalytic surface for the production of molecular hydrogen

Krassen

Stripp

Abendroth

et al. 2009

Journal of Biotechnology

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“…The enzyme may be inactivated under oxidative anaerobic or aerobic conditions, and provided inactivation is fast, this may actually protect the enzyme against further oxidative damage. Hydrogenases may be inhibited by oxygen, but depending on the enzyme and on its redox state, this inhibition can be fully irreversible (reduced FeFe hydrogenase from D. desulfuricans), 173 partly reversible (reduced FeFe hydrogenase from C. acetobutylicum), 370 fully reversible (enzymes from Ralstonia sp. ), 416 or irreversible under oxidizing conditions but reversed upon subsequent reduction in a process whose complex kinetics reveals the heterogeneity of the oxidized inactive state (typical NiFe hydrogenases).…”

Section: Redox-dependent Slow or Irreversible (In)activation Processesmentioning

confidence: 99%