Vanadium nitrogenase

Last updated
Azotobacter sp. cells, stained with Heidenhain's iron hematoxylin, x1000. Vanadium Nitrogenases are found in members of the bacteria genus Azotobacter as well as the species R. palustris and A. variabilis Azotobacter cells.jpg
Azotobacter sp. cells, stained with Heidenhain's iron hematoxylin, ×1000. Vanadium Nitrogenases are found in members of the bacteria genus Azotobacter as well as the species R. palustris and A. variabilis

Vanadium nitrogenase is a key enzyme for nitrogen fixation found in nitrogen-fixing bacteria, and is used as an alternative to molybdenum nitrogenase when molybdenum is unavailable. [1] Vanadium nitrogenases are an important biological use of vanadium, which is uncommonly used by life. An important component of the nitrogen cycle, vanadium nitrogenase converts nitrogen gas to ammonia, thereby making otherwise inaccessible nitrogen available to plants. Unlike molybdenum nitrogenase, vanadium nitrogenase can also reduce carbon monoxide to ethylene, ethane and propane [3] but both enzymes can reduce protons to hydrogen gas and acetylene to ethylene.

Contents

Biological functions

Vanadium nitrogenases are found in members of the bacterial genus Azotobacter as well as the species Rhodopseudomonas palustris and Anabaena variabilis . [1] [2] Most of the functions of vanadium nitrogenase match those of the more common molybdenum nitrogenases and serve as an alternative pathway for nitrogen fixation in molybdenum deficient conditions. [4] Like molybdenum nitrogenase, dihydrogen functions as a competitive inhibitor and carbon monoxide functions as a non-competitive inhibitor of nitrogen fixation. [5] Vanadium nitrogenase has an α2β2Ύ2 subunit structure while molybdenum nitrogenase has an α2β2 structure. Though the structural genes encoding vanadium nitrogenase show only about 15% conservation with molybdenum nitrogenases, the two nitrogenases share the same type of iron-sulphur redox centers. At room temperature, vanadium nitrogenase is less efficient at fixing nitrogen than molybdenum nitrogenases because it converts more H+ to H2 as a side reaction. [4] However, at low temperatures vanadium nitrogenases have been found to be more active than the molybdenum type, and at temperatures as low as 5 °C its nitrogen-fixing activity is 10 times higher than that of molybdenum nitrogenase. [6] Like molybdenum nitrogenase, vanadium nitrogenase is easily oxidized and is thus only active under anaerobic conditions. Various bacteria employ complex protection mechanisms to avoid oxygen. [1]

The overall stoichiometry of nitrogen fixation catalyzed by vanadium nitrogenase can be summarized as follows: [1]

N2 + 12e− + 14H+ + 24MgATP → 2NH4+ + 3H2 + 24MgADP + 24HPO42−

The crystal structure of A. vinelandii vanadium nitrogenase was resolved in 2017 ( PDB: 5N6Y ​). Compared to Mo nitrogenase, V nitrogenase replaces one sulfide in the active site with a bridging ligand. [7]

Carbon monoxide reduction

Research at the University of California Irvine showed the ability of vanadium nitrogenase to convert carbon monoxide into trace amounts of propane, ethylene, and ethane in the absence of nitrogen [3] [8] through the reduction of carbon monoxide by dithionite and ATP hydrolysis . The process of forming these hydrocarbons is carried out through proton and electron transfer in which short carbon chains are formed [8] and may ultimately allow the production of hydrocarbon fuel from CO at an industrial scale. [9]

Related Research Articles

<span class="mw-page-title-main">Hydrocarbon</span> Organic compound consisting entirely of hydrogen and carbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases, liquids, low melting solids or polymers.

Nitrogen fixation is a chemical process by which molecular nitrogen (N
2), which has a strong triple covalent bond, is converted into ammonia (NH
3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).

<span class="mw-page-title-main">Ethane</span> Organic compound (H3C–CH3)

Ethane is an organic chemical compound with chemical formula C
2H
6. At standard temperature and pressure, ethane is a colorless, odorless gas. Like many hydrocarbons, ethane is isolated on an industrial scale from natural gas and as a petrochemical by-product of petroleum refining. Its chief use is as feedstock for ethylene production.

Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like odor.

Diazotrophs are bacteria and archaea that fix gaseous nitrogen in the atmosphere into a more usable form such as ammonia.

<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 key 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.

<i>Azotobacter</i> Genus of bacteria

Azotobacter is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes that play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is inaccessible to plants, and releasing it in the form of ammonium ions into the soil. In addition to being a model organism for studying diazotrophs, it is used by humans for the production of biofertilizers, food additives, and some biopolymers. The first representative of the genus, Azotobacter chroococcum, was discovered and described in 1901 by Dutch microbiologist and botanist Martinus Beijerinck. Azotobacter species are Gram-negative bacteria found in neutral and alkaline soils, in water, and in association with some plants.

Azotobacter vinelandii is Gram-negative diazotroph that can fix nitrogen while grown aerobically. These bacteria are easily cultured and grown.

<span class="mw-page-title-main">Hydrodesulfurization</span> Chemical process used to remove sulfur in natural gas and oil refining

Hydrodesulfurization (HDS), also called hydrotreatment or hydrotreating, is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products, such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils. The purpose of removing the sulfur, and creating products such as ultra-low-sulfur diesel, is to reduce the sulfur dioxide emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.

<i>Rhodospirillum rubrum</i> Species of bacterium

Rhodospirillum rubrum is a Gram-negative, pink-coloured bacterium, with a size of 800 to 1000 nanometers. It is a facultative anaerobe, thus capable of using oxygen for aerobic respiration under aerobic conditions, or an alternative terminal electron acceptor for anaerobic respiration under anaerobic conditions. Alternative terminal electron acceptors for R. rubrum include dimethyl sulfoxide or trimethylamine oxide.

Bioorganometallic chemistry is the study of biologically active molecules that contain carbon directly bonded to metals or metalloids. The importance of main-group and transition-metal centers has long been recognized as important to the function of enzymes and other biomolecules. However, only a small subset of naturally-occurring metal complexes and synthetically prepared pharmaceuticals are organometallic; that is, they feature a direct covalent bond between the metal(loid) and a carbon atom. The first, and for a long time, the only examples of naturally occurring bioorganometallic compounds were the cobalamin cofactors (vitamin B12) in its various forms. In the 21st century, discovery of new systems containing carbon-metal bonds in biology, bioorganometallic chemistry is rapidly emerging as a distinct subdiscipline of bioinorganic chemistry that straddles organometallic chemistry and biochemistry. Naturally occurring bioorganometallics include enzymes and sensor proteins. Also within this realm are synthetically prepared organometallic compounds that serve as new drugs and imaging agents (technetium-99m sestamibi) as well as the principles relevant to the toxicology of organometallic compounds (e.g., methylmercury). Consequently, bioorganometallic chemistry is increasingly relevant to medicine and pharmacology.

<span class="mw-page-title-main">Transition metal dinitrogen complex</span> Coordination compounds with N2

Transition metal dinitrogen complexes are coordination compounds that contain transition metals as ion centers the dinitrogen molecules (N2) as ligands.

<i>Rhodopseudomonas palustris</i> Species of bacterium

Rhodopseudomonas palustris is a rod-shaped, Gram-negative purple nonsulfur bacterium, notable for its ability to switch between four different modes of metabolism.

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

The Nif regulon is a set of seven operons used to regulate nitrogen fixation in the coliform bacterium Klebsiella pneumoniae under anaerobic and microaerophilic conditions. It includes 17 nif genes, and is situated between the his and the Shi-A operon of the bacterium.

<span class="mw-page-title-main">FeMoco</span> Cofactor of nitrogenase

FeMoco (FeMo cofactor) is the primary cofactor of nitrogenase. Nitrogenase is the enzyme that catalyzes the conversion of atmospheric nitrogen molecules N2 into ammonia (NH3) through the process known as nitrogen fixation. Studying FeMoco's role in the reaction mechanism for nitrogen fixation is a potential use case for quantum computers. Even limited quantum computers could enable better simulations of the reaction mechanism.

<i>Cyanothece</i> Genus of bacteria

Cyanothece is a genus of unicellular, diazotrophic, oxygenic photosynthesizing cyanobacteria.

<i>Azotobacter chroococcum</i> Species of bacterium

Azotobacter chroococcum is a bacterium that has the ability to fix atmospheric nitrogen. It was discovered by Martinus Beijerinck in 1901, and was the first aerobic, free-living nitrogen fixer discovered. A. chroococcum could be useful for nitrogen fixation in crops as a biofertilizer, fungicide, and nutrient indicator, and in bioremediation.

<span class="mw-page-title-main">Steam cracking</span> Petrochemical process to break down saturated hydrocarbons in smaller molecules

Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons. It is the principal industrial method for producing the lighter alkenes, including ethene and propene. Steam cracker units are facilities in which a feedstock such as naphtha, liquefied petroleum gas (LPG), ethane, propane or butane is thermally cracked through the use of steam in steam cracking furnaces to produce lighter hydrocarbons. The propane dehydrogenation process may be accomplished through different commercial technologies. The main differences between each of them concerns the catalyst employed, design of the reactor and strategies to achieve higher conversion rates.

<span class="mw-page-title-main">Vanadium cycle</span> Exchange of vanadium between continental crust and seawater

The global vanadium cycle is controlled by physical and chemical processes that drive the exchange of vanadium between its two main reservoirs: the upper continental crust and the ocean. Anthropogenic processes such as coal and petroleum production release vanadium to the atmosphere.

<span class="mw-page-title-main">Abiological nitrogen fixation using homogeneous catalysts</span> Chemical process that converts nitrogen to ammonia

Abiological nitrogen fixation describes chemical processes that fix (react with) N2, usually with the goal of generating ammonia. The dominant technology for abiological nitrogen fixation is the Haber process, which uses an iron-based heterogeneous catalysts and H2 to convert N2 to NH3. This article focuses on homogeneous (soluble) catalysts for the same or similar conversions.

References

  1. 1 2 3 4 5 Rehder D. (2000). "Vanadium Nitrogenase". Journal of Inorganic Biochemistry. 80 (1–2): 133–6. doi:10.1016/S0162-0134(00)00049-0. PMID   10885473.
  2. 1 2 Larimer; et al. (2004). "Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris". Nature Biotechnology. 22 (1): 55–61. doi: 10.1038/nbt923 . PMID   14704707.
  3. 1 2 Hadlington S. "Nitrogenase Found to be a Two-Trick Pony". Royal Society of Chemistry. Retrieved 2010-08-05.
  4. 1 2 Eady R. R. (1989). "The Vanadium Nitrogenase of Azotobacter". Polyhedron. 8 (13/14): 1695–1700. doi:10.1016/S0277-5387(00)80619-1.
  5. ↑ Janas Z.; Sobota P. (2005). "Aryloxo and thiolato vanadiumnext term complexes as chemical models of the active site of nitrogenase". Coordination Chemistry Reviews. 249 (21–22): 2144–2155. doi:10.1016/j.ccr.2005.04.007.
  6. ↑ Miller R. W.; Eady R. R. (1988). "Molybdenum and vanadium nitrogenases of Azotobacter chroococcum. Low temperature favours N2 reduction by vanadium nitrogenase". Biochemical Journal. 256 (2): 429–32. doi:10.1042/bj2560429. PMC   1135427 . PMID   3223922.
  7. ↑ Sippel, D; Einsle, O (September 2017). "The structure of vanadium nitrogenase reveals an unusual bridging ligand". Nature Chemical Biology. 13 (9): 956–960. doi:10.1038/nchembio.2428. PMC   5563456 . PMID   28692069.
  8. 1 2 Lee C. C.; Hu Y.; Ribbe M. (2010). "Vanadium Nitrogenase Reduces CO". Science. 329 (5992): 642. Bibcode:2010Sci...329..642L. doi:10.1126/science.1191455. PMC   3141295 . PMID   20689010.
  9. ↑ Bland E. "Gasoline from Thin Air?". Discovery News. Retrieved 2010-08-05.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.