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Chemical Reviews May 2023The Fischer-Tropsch (FT) process converts a mixture of CO and H into liquid hydrocarbons as a major component of the gas-to-liquid technology for the production of... (Review)
Review
The Fischer-Tropsch (FT) process converts a mixture of CO and H into liquid hydrocarbons as a major component of the gas-to-liquid technology for the production of synthetic fuels. Contrary to the energy-demanding chemical FT process, the enzymatic FT-type reactions catalyzed by nitrogenase enzymes, their metalloclusters, and synthetic mimics utilize H and e as the reducing equivalents to reduce CO, CO, and CN into hydrocarbons under ambient conditions. The C chemistry exemplified by these FT-type reactions is underscored by the structural and electronic properties of the nitrogenase-associated metallocenters, and recent studies have pointed to the potential relevance of this reactivity to nitrogenase mechanism, prebiotic chemistry, and biotechnological applications. This review will provide an overview of the features of nitrogenase enzymes and associated metalloclusters, followed by a detailed discussion of the activities of various nitrogenase-derived FT systems and plausible mechanisms of the enzymatic FT reactions, highlighting the versatility of this unique reactivity while providing perspectives onto its mechanistic, evolutionary, and biotechnological implications.
Topics: Nitrogenase; Hydrocarbons; Biotechnology
PubMed: 36542730
DOI: 10.1021/acs.chemrev.2c00612 -
Journal of Biological Inorganic... Mar 2015Nitrogenase catalyzes biological nitrogen fixation, a key step in the global nitrogen cycle. Three homologous nitrogenases have been identified to date, along with... (Review)
Review
Nitrogenase catalyzes biological nitrogen fixation, a key step in the global nitrogen cycle. Three homologous nitrogenases have been identified to date, along with several structural and/or functional homologs of this enzyme that are involved in nitrogenase assembly, bacteriochlorophyll biosynthesis and methanogenic process, respectively. In this article, we provide an overview of the structures and functions of nitrogenase and its homologs, which highlights the similarity and disparity of this uniquely versatile group of enzymes.
Topics: Azotobacter vinelandii; Bacteriochlorophylls; Catalysis; Molybdenum; Nitrogen; Nitrogen Fixation; Nitrogenase; Structure-Activity Relationship
PubMed: 25491285
DOI: 10.1007/s00775-014-1225-3 -
Chemical Reviews Jun 2020Nitrogenase is the only enzyme capable of reducing N to NH. This challenging reaction requires the coordinated transfer of multiple electrons from the reductase,... (Review)
Review
Nitrogenase is the only enzyme capable of reducing N to NH. This challenging reaction requires the coordinated transfer of multiple electrons from the reductase, Fe-protein, to the catalytic component, MoFe-protein, in an ATP-dependent fashion. In the last two decades, there have been significant advances in our understanding of how nitrogenase orchestrates electron transfer (ET) from the Fe-protein to the catalytic site of MoFe-protein and how energy from ATP hydrolysis transduces the ET processes. In this review, we summarize these advances, with focus on the structural and thermodynamic redox properties of nitrogenase component proteins and their complexes, as well as on new insights regarding the mechanism of ET reactions during catalysis and how they are coupled to ATP hydrolysis. We also discuss recently developed chemical, photochemical, and electrochemical methods for uncoupling substrate reduction from ATP hydrolysis, which may provide new avenues for studying the catalytic mechanism of nitrogenase.
Topics: Adenosine Triphosphate; Biocatalysis; Electrochemical Techniques; Electron Transport; Hydrolysis; Models, Molecular; Nitrogenase; Photochemical Processes
PubMed: 31999100
DOI: 10.1021/acs.chemrev.9b00663 -
Chemical Reviews Jun 2020Nitrogenases are responsible for biological nitrogen fixation, a crucial step in the biogeochemical nitrogen cycle. These enzymes utilize a two-component protein system... (Review)
Review
Nitrogenases are responsible for biological nitrogen fixation, a crucial step in the biogeochemical nitrogen cycle. These enzymes utilize a two-component protein system and a series of iron-sulfur clusters to perform this reaction, culminating at the FeMco active site (M = Mo, V, Fe), which is capable of binding and reducing N to 2NH. In this review, we summarize how different spectroscopic approaches have shed light on various aspects of these enzymes, including their structure, mechanism, alternative reactivity, and maturation. Synthetic model chemistry and theory have also played significant roles in developing our present understanding of these systems and are discussed in the context of their contributions to interpreting the nature of nitrogenases. Despite years of significant progress, there is still much to be learned from these enzymes through spectroscopic means, and we highlight where further spectroscopic investigations are needed.
Topics: Metals, Heavy; Models, Molecular; Nitrogenase; Spectrum Analysis
PubMed: 32237739
DOI: 10.1021/acs.chemrev.9b00650 -
Biochimica Et Biophysica Acta 2013Nitrogenase contains two unique metalloclusters: the P-cluster and the M-cluster. The assembly processes of P- and M-clusters are arguably the most complicated processes... (Review)
Review
Nitrogenase contains two unique metalloclusters: the P-cluster and the M-cluster. The assembly processes of P- and M-clusters are arguably the most complicated processes in bioinorganic chemistry. There is considerable interest in decoding the biosynthetic mechanisms of the P- and M-clusters, because these clusters are not only biologically important, but also chemically unprecedented. Understanding the assembly mechanisms of these unique metalloclusters is crucial for understanding the structure-function relationship of nitrogenase. Here, we review the recent advances in this research area, with an emphasis on our work that provide important insights into the biosynthetic pathways of these high-nuclearity metal centers. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
Topics: Models, Molecular; Nitrogenase; Protein Conformation
PubMed: 23232096
DOI: 10.1016/j.bbabio.2012.12.001 -
Chembiochem : a European Journal of... Jun 2020The nitrogenase superfamily comprises homologous enzyme systems that carry out fundamentally important processes, including the reduction of N and CO, and the...
The nitrogenase superfamily comprises homologous enzyme systems that carry out fundamentally important processes, including the reduction of N and CO, and the biosynthesis of bacteriochlorophyll and coenzyme F430. This special issue provides a cross-disciplinary overview of the ongoing research in this highly diverse and unique research area of metalloprotein biochemistry.
Topics: Metalloproteins; Nitrogenase; Oxidation-Reduction
PubMed: 32426925
DOI: 10.1002/cbic.202000279 -
Chemical Reviews Jun 2020Nitrogenase is the enzyme that catalyzes biological N reduction to NH. This enzyme achieves an impressive rate enhancement over the uncatalyzed reaction. Given the high... (Review)
Review
Nitrogenase is the enzyme that catalyzes biological N reduction to NH. This enzyme achieves an impressive rate enhancement over the uncatalyzed reaction. Given the high demand for N fixation to support food and chemical production and the heavy reliance of the industrial Haber-Bosch nitrogen fixation reaction on fossil fuels, there is a strong need to elucidate how nitrogenase achieves this difficult reaction under benign conditions as a means of informing the design of next generation synthetic catalysts. This Review summarizes recent progress in addressing how nitrogenase catalyzes the reduction of an array of substrates. New insights into the mechanism of N and proton reduction are first considered. This is followed by a summary of recent gains in understanding the reduction of a number of other nitrogenous compounds not considered to be physiological substrates. Progress in understanding the reduction of a wide range of C-based substrates, including CO and CO, is also discussed, and remaining challenges in understanding nitrogenase substrate reduction are considered.
Topics: Biocatalysis; Carbon Dioxide; Carbon Monoxide; Isoenzymes; Models, Molecular; Nitrogen; Nitrogenase; Oxidation-Reduction; Substrate Specificity
PubMed: 32176472
DOI: 10.1021/acs.chemrev.9b00556 -
Chemical Reviews Jun 2020The reduction of dinitrogen to ammonia by nitrogenase reflects a complex choreography involving two component proteins, MgATP and reductant. At center stage of this... (Review)
Review
The reduction of dinitrogen to ammonia by nitrogenase reflects a complex choreography involving two component proteins, MgATP and reductant. At center stage of this process resides the active site cofactor, a complex metallocluster organized around a trigonal prismatic arrangement of iron sites surrounding an interstitial carbon. As a consequence of the choreography, electrons and protons are delivered to the active site for transfer to the bound N. While the detailed mechanism for the substrate reduction remains enigmatic, recent developments highlight the role of hydrides and the privileged role for two irons of the trigonal prism in the binding of exogenous ligands. Outstanding questions concern the precise nature of the intermediates between N and NH, and whether the cofactor undergoes significant rearrangement during turnover; resolution of these issues will require the convergence of biochemistry, structure, spectroscopy, computation, and model chemistry.
Topics: Ammonia; Crystallization; Metals, Heavy; Models, Molecular; Nitrogen; Nitrogenase; Protein Conformation
PubMed: 32538623
DOI: 10.1021/acs.chemrev.0c00067 -
MBio Jun 2022Engineering plants to synthesize nitrogenase and assimilate atmospheric N will reduce crop dependency on industrial N fertilizers. This technology can be achieved by...
Engineering plants to synthesize nitrogenase and assimilate atmospheric N will reduce crop dependency on industrial N fertilizers. This technology can be achieved by expressing prokaryotic nitrogen fixation gene products for the assembly of a functional nitrogenase in plants. NifB is a critical nitrogenase component since it catalyzes the first committed step in the biosynthesis of all types of nitrogenase active-site cofactors. Here, we used a library of 30 distinct sequences originating from different phyla and ecological niches to restore diazotrophic growth of an Azotobacter vinelandii mutant. Twenty of these variants rescued the mutant phenotype despite their phylogenetic distance to A. vinelandii. Because multiple protein interactions are required in the iron-molybdenum cofactor (FeMo-co) biosynthetic pathway, the maturation of nitrogenase in a heterologous host can be divided in independent modules containing interacting proteins that function together to produce a specific intermediate. Therefore, functional modules composed of a variant, together with the A. vinelandii NifS and NifU proteins (for biosynthesis of NifB [FeS] clusters) and the FdxN ferredoxin (for NifB function), were expressed in Nicotiana benthamiana chloroplasts and mitochondria. Three archaeal NifB proteins accumulated at high levels in soluble fractions of chloroplasts (Methanosarcina acetivorans and Methanocaldococcus infernus) or mitochondria ( and Methanothermobacter thermautotrophicus). These NifB proteins were shown to accept [FeS] clusters from NifU and were functional in FeMo-co synthesis . The accumulation of significant levels of soluble and functional NifB proteins in chloroplasts and mitochondria is critical to engineering biological nitrogen fixation in plants. Biological nitrogen fixation is the conversion of inert atmospheric dinitrogen gas into nitrogen-reactive ammonia, a reaction catalyzed by the nitrogenase enzyme of diazotrophic bacteria and archaea. Because plants cannot fix their own nitrogen, introducing functional nitrogenase in cereals and other crop plants would reduce our strong dependency on N fertilizers. NifB is required for the biosynthesis of the active site cofactors of all nitrogenases, which arguably makes it the most important protein in global nitrogen fixation. NifB functionality is therefore a requisite to engineer a plant nitrogenase. The expression of genes from a wide range of prokaryotes into the model diazotroph Azotobacter vinelandii shows a surprising level of genetic complementation suggestive of plasticity in the nitrogenase biosynthetic pathway. In addition, we obtained NifB proteins from both mitochondria and chloroplasts of tobacco that are functional after reconstitution by providing [FeS] clusters from NifU, paving the way to nitrogenase cofactor biosynthesis in plants.
Topics: Archaeal Proteins; Azotobacter vinelandii; Bacterial Proteins; Chloroplasts; Fertilizers; Iron Compounds; Mitochondria; Nitrogen; Nitrogen Fixation; Nitrogenase; Phylogeny; Nicotiana
PubMed: 35695456
DOI: 10.1128/mbio.00268-22 -
Biochimica Et Biophysica Acta 2013Nitrogenase is an enzyme found in many bacteria and archaea that catalyzes biological dinitrogen fixation, the reduction of N2 to NH3, accounting for the major input of... (Review)
Review
Nitrogenase is an enzyme found in many bacteria and archaea that catalyzes biological dinitrogen fixation, the reduction of N2 to NH3, accounting for the major input of fixed nitrogen into the biogeochemical N cycle. In addition to reducing N2 and protons, nitrogenase can reduce a number of small, non-physiological substrates. Among these alternative substrates are included a wide array of carbon-containing compounds. These compounds have provided unique insights into aspects of the nitrogenase mechanism. Recently, it was shown that carbon monoxide (CO) and carbon dioxide (CO2) can also be reduced by nitrogenase to yield hydrocarbons, opening new insights into the mechanism of small molecule activation and reduction by this complex enzyme as well as providing clues for the design of novel molecular catalysts. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
Topics: Carbon; Models, Molecular; Nitrogenase; Oxidation-Reduction
PubMed: 23597875
DOI: 10.1016/j.bbabio.2013.04.003