Ferredoxin hydrogenase

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Ferredoxin hydrogenase.png
A cartoon depiction of the enzyme ferredoxin hydrogenase
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EC no. 1.12.7.2
CAS no. 9080-02-8
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In enzymology, ferredoxin hydrogenase (EC 1.12.7.2), also referred to as [Fe-Fe]hydrogenase, H2 oxidizing hydrogenase, H2 producing hydrogenase, bidirectional hydrogenase, hydrogenase (ferredoxin), hydrogenlyase, and uptake hydrogenase, is found in Clostridium pasteurianum, Clostridium acetobutylicum,Chlamydomonas reinhardtii, and other organisms. The systematic name of this enzyme is hydrogen:ferredoxin oxidoreductase [1] [2]

Contents

Ferredoxin hydrogenase belongs to the family of oxidoreductases, specifically those acting on hydrogen as donor with an iron-sulfur protein as acceptor. Ferredoxin hydrogenase has an active metallocluster site referred to as an "H-cluster" or "H domain" that is involved in the inter-conversion of protons and electrons with hydrogen gas.

Enzyme reaction and mechanism

Ferredoxin hydrogenase catalyzes the following reversible reaction:
H2 + 2 oxidized ferredoxin 2 reduced ferredoxin + 2 H+

The exact mechanism by which this reaction occurs is still not entirely known; however, several intermediates have been identified in steady-state conditions. [2] A proposed mechanism for the catalyzed reaction by ferredoxin hydrogenase is:

Ferredoxin hydrogenase mechanism.jpg

The two substrates of this enzyme are H2 and oxidized ferredoxin, whereas its two products are reduced ferredoxin and H+. During the hydrogen gas turnover, the H-cluster undergoes a series of redox transitions as protons are translocated. [2] The reaction rate is dependent on the environment pH and sees an activity increase in pH environments between 7–9. [3] Accessory clusters allow for the enzyme to retain full enzyme activity at potentials around and higher than the equilibrium potential. However, it is important to note that the accessory clusters are not as effective at extremely low potentials. [4]

Enzyme structure

The reaction occurs in the [2Fe] moiety of the active H cluster site, which also includes a [4Fe4S] cluster covalently bonded via a cysteinyl thiolate. An additional accessory site known as the F-domain, which contains four Fe-S clusters, is known as the main gate for electron transfer to and from the catalytic site. [4] The [2Fe] sub-site is coordinated by several CO and CN ligands and an azadithiolate bridge that allows for proton shuttling. [2] The oxidized state of the sub-site, abbreviated as Hox, includes a paramagnetic, mixed-valence [Fe(I)Fe(II)] moiety and a diamagnetic, oxidized [4Fe4S] 2+ cluster. [2] The single electron reduction of Hox yields two protomers that differ in the localization of the added electron and proton. [2] The addition of the second electron results in the [Fe(I)Fe(II)]-[4Fe4S]+ configuration and a protonated azadithiolate bridge.

Biological function

Hydrogenases are found in prokaryotes, lower eukaryotes, and archaea. This broad category of metalloenzymes can be divided into [NiFe], [FeFe], and [Fe] variants based on the transition metals found in their active sites. However, the hydrogen gas oxidation and proton reduction activities varies greatly among the variants and even within their own subcategories. [1] Ferredoxin hydrogenase participates in glyoxylate and dicarboxylate metabolism and methane metabolism. It has 3 cofactors: iron, Sulfur, and Nickel.

Ferredoxin hydrogenase found in the green algae Chlamydomonas reinhardtii use supplied electrons from photosystem I to reduce protons into hydrogen gas. This electron supply transfer is possible through photosystem I interactions with photosynthetic electron transfer ferredoxin (PetF). [5] [6] The inter-conversion of protons and electrons with hydrogen gas allow organisms to modulate energy input and output, adjust organelle redox potential, and transduce chemical signals. [7]

Industrial significance

Hydrogen gas is a potential candidate for the partial replacement of fossil fuels as a clean energy carrier in fuel cells. However, because of the gas's weight, it often escapes the Earth's atmosphere into space, making it a scarce resource on Earth. [8]

The hydrogen photo-production in green algae, catalyzed by ferredoxin hydrogenase, is a potential source of hydrogen gas. Unfortunately, the inefficiency of the reaction and enzyme as whole to produce hydrogen places a barrier on the viability of this reaction on an industrial scale. [9] In addition, ferredoxin hydrogenase is sensitive to oxygen; the typical half life for the enzyme under aerobic conditions is on the scale of seconds, rendering it difficult to cultivate and manage commercially. [9]

Related Research Articles

<i>Chlamydomonas reinhardtii</i> Species of alga

Chlamydomonas reinhardtii is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an eyespot that senses light.

<span class="mw-page-title-main">Nitrogenase</span> Class of enzymes

Nitrogenases are enzymes (EC 1.18.6.1EC 1.19.6.1) that are produced by certain bacteria, such as cyanobacteria (blue-green bacteria) and rhizobacteria. These enzymes are responsible for the reduction of nitrogen (N2) to ammonia (NH3). Nitrogenases are the only family of enzymes known to catalyze this reaction, which is a step in the process of nitrogen fixation. Nitrogen fixation is required for all forms of life, with nitrogen being essential for the biosynthesis of molecules (nucleotides, amino acids) that create plants, animals and other organisms. They are encoded by the Nif genes or homologs. They are related to protochlorophyllide reductase.

<span class="mw-page-title-main">Photosystem I</span> Second protein complex in photosynthetic light reactions

Photosystem I is one of two photosystems in the photosynthetic light reactions of algae, plants, and cyanobacteria. Photosystem I is an integral membrane protein complex that uses light energy to catalyze the transfer of electrons across the thylakoid membrane from plastocyanin to ferredoxin. Ultimately, the electrons that are transferred by Photosystem I are used to produce the moderate-energy hydrogen carrier NADPH. The photon energy absorbed by Photosystem I also produces a proton-motive force that is used to generate ATP. PSI is composed of more than 110 cofactors, significantly more than Photosystem II.

Ferredoxins are iron–sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C. Wharton of the DuPont Co. and applied to the "iron protein" first purified in 1962 by Mortenson, Valentine, and Carnahan from the anaerobic bacterium Clostridium pasteurianum.

<span class="mw-page-title-main">Photophosphorylation</span> Biochemical process in photosynthesis

In the process of photosynthesis, the phosphorylation of ADP to form ATP using the energy of sunlight is called photophosphorylation. Cyclic photophosphorylation occurs in both aerobic and anaerobic conditions, driven by the main primary source of energy available to living organisms, which is sunlight. All organisms produce a phosphate compound, ATP, which is the universal energy currency of life. In photophosphorylation, light energy is used to pump protons across a biological membrane, mediated by flow of electrons through an electron transport chain. This stores energy in a proton gradient. As the protons flow back through an enzyme called ATP synthase, ATP is generated from ADP and inorganic phosphate. ATP is essential in the Calvin cycle to assist in the synthesis of carbohydrates from carbon dioxide and NADPH.

Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis to convert sunlight, water, and carbon dioxide into carbohydrates and oxygen. The term artificial photosynthesis is commonly used to refer to any scheme for capturing and storing the energy from sunlight in the chemical bonds of a fuel. Photocatalytic water splitting converts water into hydrogen and oxygen and is a major research topic of artificial photosynthesis. Light-driven carbon dioxide reduction is another process studied that replicates natural carbon fixation.

Iron–sulfur proteins are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states. Iron–sulfur clusters are found in a variety of metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase, hydrogenases, coenzyme Q – cytochrome c reductase, succinate – coenzyme Q reductase and nitrogenase. Iron–sulfur clusters are best known for their role in the oxidation-reduction reactions of electron transport in mitochondria and chloroplasts. Both Complex I and Complex II of oxidative phosphorylation have multiple Fe–S clusters. They have many other functions including catalysis as illustrated by aconitase, generation of radicals as illustrated by SAM-dependent enzymes, and as sulfur donors in the biosynthesis of lipoic acid and biotin. Additionally, some Fe–S proteins regulate gene expression. Fe–S proteins are vulnerable to attack by biogenic nitric oxide, forming dinitrosyl iron complexes. In most Fe–S proteins, the terminal ligands on Fe are thiolate, but exceptions exist.

A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H2), as shown below:

Cytochrome b<sub>6</sub>f complex Enzyme

The cytochrome b6f complex (plastoquinol/plastocyanin reductase or plastoquinol/plastocyanin oxidoreductase; EC 7.1.1.6) is an enzyme found in the thylakoid membrane in chloroplasts of plants, cyanobacteria, and green algae, that catalyzes the transfer of electrons from plastoquinol to plastocyanin:

<span class="mw-page-title-main">Photosynthetic reaction centre</span> Molecular unit responsible for absorbing light in photosynthesis

A photosynthetic reaction center is a complex of several proteins, pigments and other co-factors that together execute the primary energy conversion reactions of photosynthesis. Molecular excitations, either originating directly from sunlight or transferred as excitation energy via light-harvesting antenna systems, give rise to electron transfer reactions along the path of a series of protein-bound co-factors. These co-factors are light-absorbing molecules (also named chromophores or pigments) such as chlorophyll and pheophytin, as well as quinones. The energy of the photon is used to excite an electron of a pigment. The free energy created is then used, via a chain of nearby electron acceptors, for a transfer of hydrogen atoms (as protons and electrons) from H2O or hydrogen sulfide towards carbon dioxide, eventually producing glucose. These electron transfer steps ultimately result in the conversion of the energy of photons to chemical energy.

<span class="mw-page-title-main">Biohydrogen</span>

Biohydrogen is H2 that is produced biologically. Interest is high in this technology because H2 is a clean fuel and can be readily produced from certain kinds of biomass, including biological waste. Furthermore some photosynthetic microorganisms are capable to produce H2 directly from water splitting using light as energy source.

<i>Cupriavidus necator</i> Species of bacterium

Cupriavidus necator is a Gram-negative soil bacterium of the class Betaproteobacteria.

Hydrogen-oxidizing bacteria are a group of facultative autotrophs that can use hydrogen as an electron donor. They can be divided into aerobes and anaerobes. The former use hydrogen as an electron donor and oxygen as an acceptor while the latter use sulphate or nitrogen dioxide as electron acceptors. Species of both types have been isolated from a variety of environments, including fresh waters, sediments, soils, activated sludge, hot springs, hydrothermal vents and percolating water.

A hydrogenase mimic or bio-mimetic is an enzyme mimic of hydrogenases.

In enzymology, carbon monoxide dehydrogenase (CODH) (EC 1.2.7.4) is an enzyme that catalyzes the chemical reaction

<span class="mw-page-title-main">High potential iron–sulfur protein</span>

High potential iron-sulfur proteins (HIPIP) are a class of iron-sulfur proteins. They are ferredoxins that participate in electron transfer in photosynthetic bacteria as well as in Paracoccus denitrificans.

An enzymatic biofuel cell is a specific type of fuel cell that uses enzymes as a catalyst to oxidize its fuel, rather than precious metals. Enzymatic biofuel cells, while currently confined to research facilities, are widely prized for the promise they hold in terms of their relatively inexpensive components and fuels, as well as a potential power source for bionic implants.

[NiFe] hydrogenase is a type of hydrogenase, which is an oxidative enzyme that reversibly converts molecular hydrogen in prokaryotes including Bacteria and Archaea. The catalytic site on the enzyme provides simple hydrogen-metabolizing microorganisms a redox mechanism by which to store and utilize energy via the reaction

Hydrogenase (NAD+, ferredoxin) (EC 1.12.1.4, bifurcating [FeFe] hydrogenase) is an enzyme with systematic name hydrogen:NAD+, ferredoxin oxidoreductase. This enzyme catalyses the following chemical reaction

The H+-translocating F420H2 Dehydrogenase (F420H2DH) Family(TC# 3.D.9) is a member of the Na+ transporting Mrp superfamily. A single F420H2 dehydrogenase (also referred to as F420H2:quinol oxidoreductase) from the methanogenic archaeon, Methanosarcina mazei Gö1, has been shown to be a redox driven proton pump. The F420H2DH of M. mazei has a molecular size of about 120 kDa and contains Fe-S clusters and FAD. A similar five-subunit enzyme has been isolated from Methanolobus tindarius. The sulfate-reducing Archaeoglobus fulgidus (and several other archaea) also have this enzyme.

References

  1. 1 2 Artz JH, Zadvornyy OA, Mulder DW, Keable SM, Cohen AE, Ratzloff MW, et al. (January 2020). "Tuning Catalytic Bias of Hydrogen Gas Producing Hydrogenases". Journal of the American Chemical Society. 142 (3): 1227–1235. doi:10.1021/jacs.9b08756. PMC   8653774 . PMID   31816235.
  2. 1 2 3 4 5 6 Lorent C, Katz S, Duan J, Kulka CJ, Caserta G, Teutloff C, et al. (March 2020). "Shedding light on proton and electron dynamics in [FeFe] hydrogenases". Journal of the American Chemical Society. 142 (12): 5493–5497. doi:10.1021/jacs.9b13075. PMID   32125830. S2CID   212407474.
  3. ↑ Diakonova AN, Khrushchev SS, Kovalenko IB, Riznichenko GY, Rubin AB (October 2016). "Influence of pH and ionic strength on electrostatic properties of ferredoxin, FNR, and hydrogenase and the rate constants of their interaction". Physical Biology. 13 (5): 056004. Bibcode:2016PhBio..13e6004D. doi:10.1088/1478-3975/13/5/056004. PMID   27716644. S2CID   30914628.
  4. 1 2 Gauquelin C, Baffert C, Richaud P, Kamionka E, Etienne E, Guieysse D, et al. (February 2018). "Roles of the F-domain in [FeFe] hydrogenase". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1859 (2): 69–77. doi: 10.1016/j.bbabio.2017.08.010 . PMID   28842179.
  5. ↑ Long H, King PW, Ghirardi ML, Kim K (April 2009). "Hydrogenase/ferredoxin charge-transfer complexes: effect of hydrogenase mutations on the complex association". The Journal of Physical Chemistry A. 113 (16): 4060–7. doi:10.1021/jp810409z. PMID   19317477.
  6. ↑ Rumpel S, Siebel JF, Diallo M, Farès C, Reijerse EJ, Lubitz W (July 2015). "Structural Insight into the Complex of Ferredoxin and [FeFe] Hydrogenase from Chlamydomonas reinhardtii". ChemBioChem. 16 (11): 1663–9. doi:10.1002/cbic.201500130. PMID   26010059. S2CID   205559427.
  7. ↑ Sickerman NS, Hu Y (2019). "Hydrogenases". In Hu Y (ed.). Metalloproteins. pp. 65–88. doi:10.1007/978-1-4939-8864-8_5. ISBN   978-1-4939-8864-8. PMID   30317475. S2CID   240028791.{{cite book}}: |work= ignored (help)
  8. ↑ Catling DC, Zahnle KJ, McKay C (August 2001). "Biogenic methane, hydrogen escape, and the irreversible oxidation of early Earth". Science. 293 (5531): 839–43. Bibcode:2001Sci...293..839C. doi:10.1126/science.1061976. PMID   11486082. S2CID   37386726.
  9. 1 2 Eilenberg H, Weiner I, Ben-Zvi O, Pundak C, Marmari A, Liran O, et al. (2016-08-30). "The dual effect of a ferredoxin-hydrogenase fusion protein in vivo: successful divergence of the photosynthetic electron flux towards hydrogen production and elevated oxygen tolerance". Biotechnology for Biofuels. 9 (1): 182. doi: 10.1186/s13068-016-0601-3 . PMC   5006448 . PMID   27582874.
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