The roles of chalcogenides in O<sub>2</sub> protection of H<sub>2</sub>ase active sites

Yang, Xuemei; Darensbourg, Marcetta Y.

doi:10.1039/d0sc02584d

Cited by 8 publications

(8 citation statements)

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“…A similar behavior was observed when the experiment was performed in the presence of HBF 4 (Figure S14). The reactivity of [FeFe] hydrogenases with O 2 has been extensively studied. − In the case of [FeFe] hydrogenase mimics, recent work points to a relationship between the reactivity with molecular oxygen and the structure of the [FeFe] bridge, the azadithiolate (adt) derivatives being very reactive whereas the propanedithiolate (pdt) derivatives exhibit reduced reactivity . The results in Figure show that 9 , having a benzenedithiolate (bdt) bridge, is also reactive toward O 2 .…”

Section: Resultsmentioning

confidence: 99%

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics

et al. 2021

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TTF-and exTTF-containing [(μ-S 2 )Fe 2 (CO) 6 ] complexes have been prepared by the photochemical reaction of TTF or exTTF and [(μ-S 2 )Fe 2 (CO) 6 ]. These complexes are able to interact with PAHs. In the absence of air and in acid media an electrocatalytic dihydrogen evolution reaction (HER) occurs, similarly to analogous [(μ-S 2 )Fe 2 (CO) 6 ] complexes. However, in the presence of air, the TTF and exTTF organic moieties strongly influence the electrochemistry of these systems. The reported data may be valuable in the design of [FeFe] hydrogenase mimics able to combine the HER properties of the [FeFe] cores with the unique TTF properties.

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Section: Resultsmentioning

confidence: 99%

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics

et al. 2021

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“…2) The advantage of having a Se at position 576 may relate directly to its position cis to that occupied by the hydride intermediate and (by extension) molecular H 2 and O 2 . This stereochemical preference suggests two options: 1) The Se atom, due to its larger size or unknown influence over the side-chain conformation, hinders the initial binding of an O 2 molecule; or 2) the greater nucleophilicity of Se promotes its attack on an electron-deficient reactive oxygen intermediate, producing a selenoxide moiety (Se-O) that is more easily reduced (compared with S-O) to release H 2 O, that is, the Se atom serves as a decoy (51).…”

Section: Discussionmentioning

confidence: 99%

Selective cysteine-to-selenocysteine changes in a [NiFe]-hydrogenase confirm a special position for catalysis and oxygen tolerance

Evans

Krahn

Murphy

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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In [NiFe]-hydrogenases, the active-site Ni is coordinated by four cysteine-S ligands (Cys; C), two of which are bridging to the Fe(CO)(CN)2 fragment. Substitution of a single Cys residue by selenocysteine (Sec; U) occurs occasionally in nature. Using a recent method for site-specific Sec incorporation into proteins, each of the four Ni-coordinating cysteine residues in the oxygen-tolerant Escherichia coli [NiFe]-hydrogenase-1 (Hyd-1) has been replaced by U to identify its importance for enzyme function. Steady-state solution activity of each Sec-substituted enzyme (on a per-milligram basis) is lowered, although this may reflect the unquantified presence of recalcitrant inactive/immature/misfolded forms. Protein film electrochemistry, however, reveals detailed kinetic data that are independent of absolute activities. Like native Hyd-1, the variants have low apparent KMH2 values, do not produce H2 at pH 6, and display the same onset overpotential for H2 oxidation. Mechanistically important differences were identified for the C576U variant bearing the equivalent replacement found in native [NiFeSe]-hydrogenases, its extreme O2 tolerance (apparent KMH2 and Vmax [solution] values relative to native Hyd-1 of 0.13 and 0.04, respectively) implying the importance of a selenium atom in the position cis to the site where exogenous ligands (H−, H2, O2) bind. Observation of the same unusual electrocatalytic signature seen earlier for the proton transfer-defective E28Q variant highlights the direct role of the chalcogen atom (S/Se) at position 576 close to E28, with the caveat that Se is less effective than S in facilitating proton transfer away from the Ni during H2 oxidation by this enzyme.

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“…In all states of standard hydrogenases, the nickel atom has a vacant or labile coordination site and, therefore, Ni represents the primary hydrogen binding site. The H 2 molecule can be accessed by the buried [NiFe] active site through hydrophobic tunnels leading to the Ni atom [ 128 , 129 , 130 , 131 ].…”

Section: Hydrogenasesmentioning

confidence: 99%

Selenium—More than Just a Fortuitous Sulfur Substitute in Redox Biology

Maia,

Maiti,

Moura

et al. 2023

Molecules

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Living organisms use selenium mainly in the form of selenocysteine in the active site of oxidoreductases. Here, selenium’s unique chemistry is believed to modulate the reaction mechanism and enhance the catalytic efficiency of specific enzymes in ways not achievable with a sulfur-containing cysteine. However, despite the fact that selenium/sulfur have different physicochemical properties, several selenoproteins have fully functional cysteine-containing homologues and some organisms do not use selenocysteine at all. In this review, selected selenocysteine-containing proteins will be discussed to showcase both situations: (i) selenium as an obligatory element for the protein’s physiological function, and (ii) selenium presenting no clear advantage over sulfur (functional proteins with either selenium or sulfur). Selenium’s physiological roles in antioxidant defence (to maintain cellular redox status/hinder oxidative stress), hormone metabolism, DNA synthesis, and repair (maintain genetic stability) will be also highlighted, as well as selenium’s role in human health. Formate dehydrogenases, hydrogenases, glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases will be herein featured.

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The roles of chalcogenides in O₂ protection of H₂ase active sites

Abstract: At some point, all HER (Hydrogen Evolution Reaction) catalysts, important in sustainable H2O splitting technology, will encounter O2 and O2-damage. The [NiFeSe]-H2ases and some of the [NiFeS]-H2ases, biocatalysts for reversible...

Cited by 8 publications

References 62 publications

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics

Selective cysteine-to-selenocysteine changes in a [NiFe]-hydrogenase confirm a special position for catalysis and oxygen tolerance

Selenium—More than Just a Fortuitous Sulfur Substitute in Redox Biology

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The roles of chalcogenides in O2 protection of H2ase active sites

Abstract: At some point, all HER (Hydrogen Evolution Reaction) catalysts, important in sustainable H2O splitting technology, will encounter O2 and O2-damage. The [NiFeSe]-H2ases and some of the [NiFeS]-H2ases, biocatalysts for reversible...

Cited by 8 publications

References 62 publications

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics

Electrocatalytic Behavior of Tetrathiafulvalene (TTF) and Extended Tetrathiafulvalene (exTTF) [FeFe] Hydrogenase Mimics

Selective cysteine-to-selenocysteine changes in a [NiFe]-hydrogenase confirm a special position for catalysis and oxygen tolerance

Selenium—More than Just a Fortuitous Sulfur Substitute in Redox Biology

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The roles of chalcogenides in O₂ protection of H₂ase active sites