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Singh T, Atreya V, Jalwal S, Anand A, Chakraborty S. Advances in Group VI Metal-Catalyzed Homogeneous Hydrogenation and Dehydrogenation Reactions. Chem Asian J 2023; 18:e202300758. [PMID: 37815164 DOI: 10.1002/asia.202300758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/10/2023] [Accepted: 10/10/2023] [Indexed: 10/11/2023]
Abstract
Transition metal-catalyzed homogeneous hydrogenation and dehydrogenation reactions for attaining plethora of organic scaffolds have evolved as a key domain of research in academia and industry. These protocols are atom-economic, greener, in line with the goal of sustainability, eventually pave the way for numerous novel environmentally benign methodologies. Appealing progress has been achieved in the realm of homogeneous catalysis utilizing noble metals. Owing to their high cost, less abundance along with toxicity issues led the scientific community to search for sustainable alternatives. In this context, earth- abundant base metals have gained substantial attention culminating enormous progress in recent years, predominantly with pincer-type complexes of nickel, cobalt, iron, and manganese. In this regard, group VI chromium, molybdenum and tungsten complexes have been overlooked and remain underdeveloped despite their earth-abundance and bio-compatibility. This review delineates a comprehensive overview in the arena of homogeneously catalysed (de)hydrogenation reactions using group VI base metals chromium, molybdenum, and tungsten till date. Various reactions have been described; hydrogenation, transfer hydrogenation, dehydrogenation, acceptorless dehydrogenative coupling, hydrogen auto transfer, along with their scope and brief mechanistic insights.
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Affiliation(s)
- Tushar Singh
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Jodhpur, 342037, Rajasthan
| | - Vaishnavi Atreya
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Jodhpur, 342037, Rajasthan
| | - Sachin Jalwal
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Jodhpur, 342037, Rajasthan
| | - Aman Anand
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Jodhpur, 342037, Rajasthan
| | - Subrata Chakraborty
- Department of Chemistry, Indian Institute of Technology Jodhpur, Karwar, Jodhpur, 342037, Rajasthan
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Winiarska A, Ramírez-Amador F, Hege D, Gemmecker Y, Prinz S, Hochberg G, Heider J, Szaleniec M, Schuller JM. A bacterial tungsten-containing aldehyde oxidoreductase forms an enzymatic decorated protein nanowire. SCIENCE ADVANCES 2023; 9:eadg6689. [PMID: 37267359 PMCID: PMC10413684 DOI: 10.1126/sciadv.adg6689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/28/2023] [Indexed: 06/04/2023]
Abstract
Aldehyde oxidoreductases (AORs) are tungsten enzymes catalyzing the oxidation of many different aldehydes to the corresponding carboxylic acids. In contrast to other known AORs, the enzyme from the denitrifying betaproteobacterium Aromatoleum aromaticum (AORAa) consists of three different subunits (AorABC) and uses nicotinamide adenine dinucleotide (NAD) as an electron acceptor. Here, we reveal that the enzyme forms filaments of repeating AorAB protomers that are capped by a single NAD-binding AorC subunit, based on solving its structure via cryo-electron microscopy. The polyferredoxin-like subunit AorA oligomerizes to an electron-conducting nanowire that is decorated with enzymatically active and W-cofactor (W-co) containing AorB subunits. Our structure further reveals the binding mode of the native substrate benzoate in the AorB active site. This, together with quantum mechanics:molecular mechanics (QM:MM)-based modeling for the coordination of the W-co, enables formulation of a hypothetical catalytic mechanism that paves the way to further engineering for applications in synthetic biology and biotechnology.
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Affiliation(s)
- Agnieszka Winiarska
- Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Kraków, Poland
| | - Fidel Ramírez-Amador
- SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg, Germany
| | - Dominik Hege
- Faculty of Biology, Philipps-University of Marburg, Marburg, Germany
| | - Yvonne Gemmecker
- Faculty of Biology, Philipps-University of Marburg, Marburg, Germany
| | - Simone Prinz
- Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Georg Hochberg
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Johann Heider
- SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg, Germany
- Faculty of Biology, Philipps-University of Marburg, Marburg, Germany
| | - Maciej Szaleniec
- Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Kraków, Poland
| | - Jan Michael Schuller
- SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg, Germany
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3
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Luo Z, Li Z, Sun J, Shi K, Lei M, Tie B, Du H. Multiple mechanisms collectively mediate tungsten homeostasis and resistance in Citrobacter sp. Lzp2. JOURNAL OF HAZARDOUS MATERIALS 2023; 448:130877. [PMID: 36731318 DOI: 10.1016/j.jhazmat.2023.130877] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 01/19/2023] [Accepted: 01/25/2023] [Indexed: 06/18/2023]
Abstract
Tungsten (W) is an emerging contaminant, and current knowledge on W resistance profiles of microorganisms remains scarce and fragmentary. This study aimed to explore the physiological responses of bacteria under W stress and to resolve genes and metabolic pathways involved in W resistance using a transcriptome expression profiling assay. The results showed that the bacterium Citrobacter sp. Lzp2, screened from W-contaminated soil, could tolerate hundreds of mM W(VI) with a 50% inhibiting concentration of ∼110 mM. To cope with W stress, Citrobacter sp. Lzp2 secreted large amounts of proteins through the type VI secretory system (T6SS) to chelate W oxoanions via carboxylic groups in extracellular polymeric substances (EPS), and could transport cytosolic W outside via the multidrug efflux pumps (mdtABC and acrD). Intracellular W is probably bound by chaperone proteins and metal-binding pterin (tungstopterin) through the sulfur relay system. We propose that tetrathionate respiration is a new metabolic pathway for cellular W detoxification likely producing thio-tungstate. We conclude that multiple mechanisms collectively mediate W homeostasis and resistance in Citrobacter sp. Lzp2. Our results have important implications not only for understanding the intricate regulatory network of W homeostasis in microbes but also for bio-recovery and bioremediation of W in contaminated environments.
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Affiliation(s)
- Zipei Luo
- College of Resources and Environment, Hunan Agricultural University, 410127 Changsha, China
| | - Zhen Li
- College of Resources and Environmental Sciences, Nanjing Agricultural University, 210095 Nanjing, China
| | - Jing Sun
- State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 550081 Guiyang, China
| | - Kaixiang Shi
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, 430070 Wuhan, China
| | - Ming Lei
- College of Resources and Environment, Hunan Agricultural University, 410127 Changsha, China
| | - Boqing Tie
- College of Resources and Environment, Hunan Agricultural University, 410127 Changsha, China
| | - Huihui Du
- College of Resources and Environment, Hunan Agricultural University, 410127 Changsha, China.
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Zhang W, Bushnell EA. A QM/MM investigation of the catalytic mechanism of acetylene hydratase: insights into engineering a more effective enzyme. CAN J CHEM 2021. [DOI: 10.1139/cjc-2020-0322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the present investigation, a QM/MM approach was used to better understand the effect of the second environmental shell of the active site on the catalytic conversion of acetylene to acetaldehyde by acetylene hydratase (AH). In addition, the effect of substituting W-coordinating sulfur atoms with selenium atoms was done to provide insight into the influence of the W-coordinating atoms on the catalytic reaction. From the results, it found that the presence of the second shell environment had a significant effect on the reaction. Specifically, in the absence of the MM second shell environment (i.e., QM-cluster model), the rate-determining step is defined by the first proton transfer step. In contrast, for the QM/MM model, the rate-determining step is defined by the water attacking step. Moreover, with the presence of the MM second shell environment, a key intermediate found in the DFT-cluster investigation does not exist in the QM/MM investigation. Rather, what was a two-step process in the DFT-cluster study was calculated to occur in a single step for the QM/MM study. Regarding the sulfur to selenium substitutions, it was found that Gibbs energy for the acetylene binding phase was significantly affected. Notably, the trans-position selenium made the binding of acetylene 65.6 kJ mol−1 less endergonic. Moreover, the overall reaction became 38.2 kJ mol−1 less endergonic compared with the wild type (WT) AH model. Thus, the substitution of key W-coordinating sulfur atoms with selenium atoms may offer a means to enhance the catalytic mechanism of AH considerably.
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Affiliation(s)
- Wenyuan Zhang
- Department of Chemistry, Brandon University, 270-18th Street, Brandon, MB R7A 6A9, Canada
- Department of Chemistry, Brandon University, 270-18th Street, Brandon, MB R7A 6A9, Canada
| | - Eric A.C. Bushnell
- Department of Chemistry, Brandon University, 270-18th Street, Brandon, MB R7A 6A9, Canada
- Department of Chemistry, Brandon University, 270-18th Street, Brandon, MB R7A 6A9, Canada
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Berasaluce I, Cseh K, Roller A, Hejl M, Heffeter P, Berger W, Jakupec MA, Kandioller W, Malarek MS, Keppler BK. The First Anticancer Tris(pyrazolyl)borate Molybdenum(IV) Complexes: Tested in Vitro and in Vivo-A Comparison of O,O-, S,O-, and N,N-Chelate Effects. Chemistry 2020; 26:2211-2221. [PMID: 31560142 PMCID: PMC7064950 DOI: 10.1002/chem.201903605] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/19/2019] [Indexed: 12/22/2022]
Abstract
The synthesis, characterization and biological activity of molybdenum(IV) complexes containing Trofimenko's scorpionato ligand, hydrotris(3-isopropylpyrazolyl)borate (TpiPr ), in addition to varying biologically active as well as other conventional ligands is described. Ligands employed include (O,O-) (S,O-) (N,N-) donors that have been successfully coordinated to the molybdenum center by means of oxygen-atom transfer (OAT) reactions from the known MoVI starting material, TpiPr MoO2 Cl. The synthesized complexes were characterized by standard analytical methods and where possible by X-ray diffraction analysis. The aqueous stability of the compounds was studied by means of UV/Vis spectroscopy and the impact of the attached ligand scaffolds on the oxidation potentials (MoIV to MoV ) was studied by cyclic voltammetry. Utilizing polyvinylpyrrolidone (PVP) as a solubilizing agent, adequate aqueous solubility for biological tests was obtained. Anticancer activity tests and preliminary mode of action studies have been performed in vitro and in vivo.
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Affiliation(s)
- Iker Berasaluce
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
| | - Klaudia Cseh
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
| | - Alexander Roller
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
| | - Michaela Hejl
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
| | - Petra Heffeter
- Research Cluster ‘Translational Cancer Therapy Research“University of ViennaWaehringer Straße 421090ViennaAustria
- Institute of Cancer Research and Comprehensive Cancer CenterMedical University of ViennaBorschkegasse 8a1090ViennaAustria
| | - Walter Berger
- Research Cluster ‘Translational Cancer Therapy Research“University of ViennaWaehringer Straße 421090ViennaAustria
- Institute of Cancer Research and Comprehensive Cancer CenterMedical University of ViennaBorschkegasse 8a1090ViennaAustria
| | - Michael A. Jakupec
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
- Research Cluster ‘Translational Cancer Therapy Research“University of ViennaWaehringer Straße 421090ViennaAustria
| | - Wolfgang Kandioller
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
- Research Cluster ‘Translational Cancer Therapy Research“University of ViennaWaehringer Straße 421090ViennaAustria
| | - Michael S. Malarek
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
| | - Bernhard K. Keppler
- Institute of Inorganic ChemistryFaculty of ChemistryUniversity of ViennaWaehringer Straße 421090ViennaAustria
- Research Cluster ‘Translational Cancer Therapy Research“University of ViennaWaehringer Straße 421090ViennaAustria
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Preiner J, Wienkoop S, Weckwerth W, Oburger E. Molecular Mechanisms of Tungsten Toxicity Differ for Glycine max Depending on Nitrogen Regime. FRONTIERS IN PLANT SCIENCE 2019; 10:367. [PMID: 31001297 PMCID: PMC6454624 DOI: 10.3389/fpls.2019.00367] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 03/08/2019] [Indexed: 05/06/2023]
Abstract
Tungsten (W) finds increasing application in military, aviation and household appliance industry, opening new paths into the environment. Since W shares certain chemical properties with the essential plant micronutrient molybdenum (Mo), it is proposed to inhibit enzymatic activity of molybdoenzymes [e.g., nitrate reductase (NR)] by replacing the Mo-ion bound to the co-factor. Recent studies suggest that W, much like other heavy metals, also exerts toxicity on its own. To create a comprehensive picture of tungsten stress, this study investigated the effects of W on growth and metabolism of soybean (Glycine max), depending on plant nitrogen regime [nitrate fed (N fed) vs. symbiotic N2 fixation (N fix)] by combining plant physiological data (biomass production, starch and nutrient content, N2 fixation, nitrate reductase activity) with root and nodule proteome data. Irrespective of N regime, NR activity and total N decreased with increasing W concentrations. Nodulation and therefore also N2 fixation strongly declined at high W concentrations, particularly in N fix plants. However, N2 fixation rate (g N fixed g-1 nodule dwt) remained unaffected by increasing W concentrations. Proteomic analysis revealed a strong decline in leghemoglobin and nitrogenase precursor levels (NifD), as well as an increase in abundance of proteins involved in secondary metabolism in N fix nodules. Taken together this indicates that, in contrast to the reported direct inhibition of NR, N2 fixation appears to be indirectly inhibited by a decrease in nitrogenase synthesis due to W induced changes in nodule oxygen levels of N fix plants. Besides N metabolism, plants exhibited a strong reduction of shoot (both N regimes) and root (N fed only) biomass, an imbalance in nutrient levels and a failure of carbon metabolic pathways accompanied by an accumulation of starch at high tungsten concentrations, independent of N-regime. Proteomic data (available via ProteomeXchange with identifier PXD010877) demonstrated that the response to high W concentrations was independent of nodule functionality and dominated by several peroxidases and other general stress related proteins. Based on an evaluation of several W responsive proteotypic peptides, we identified a set of protein markers of W stress and possible targets for improved stress tolerance.
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Affiliation(s)
- Julian Preiner
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
- Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences Vienna, Tulln, Austria
| | - Stefanie Wienkoop
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
| | - Wolfram Weckwerth
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
| | - Eva Oburger
- Department of Forest and Soil Sciences, Institute of Soil Research, University of Natural Resources and Life Sciences Vienna, Tulln, Austria
- Division of Terrestrial Ecosystem Research, Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria
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7
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Shah Idil A, Donaldson N. The use of tungsten as a chronically implanted material. J Neural Eng 2018; 15:021006. [DOI: 10.1088/1741-2552/aaa502] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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8
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Gohr S, Hrobárik P, Kaupp M. Four-Component Relativistic Density Functional Calculations of EPR Parameters for Model Complexes of Tungstoenzymes. J Phys Chem A 2017; 121:9106-9117. [DOI: 10.1021/acs.jpca.7b08768] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sebastian Gohr
- Institut
für Chemie, Theoretische Chemie/Quantenchemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany
| | - Peter Hrobárik
- Institut
für Chemie, Theoretische Chemie/Quantenchemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany
- Department
of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2, Ilkovičova 6, SK-84215 Bratislava, Slovakia
| | - Martin Kaupp
- Institut
für Chemie, Theoretische Chemie/Quantenchemie, Technische Universität Berlin, Sekr. C7, Straße des 17. Juni 135, 10623 Berlin, Germany
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9
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Theoretical exploration of the mechanism of formylmethanofuran dehydrogenase: the first reductive step in CO2 fixation by methanogens. J Biol Inorg Chem 2016; 21:703-13. [DOI: 10.1007/s00775-016-1377-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/19/2016] [Indexed: 10/21/2022]
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10
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Maurya MR, Dhaka S, Avecilla F. Synthesis, characterization, reactivity and catalytic activity of dioxidomolybdenum(VI) complexes derived from tribasic ONS donor ligands. Polyhedron 2014. [DOI: 10.1016/j.poly.2014.05.068] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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11
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Characterization and Expression Patterns of Nitrate Reductase from Dunaliella bardawil under Osmotic Stress and Dilution Shock. Appl Biochem Biotechnol 2014; 173:1274-92. [DOI: 10.1007/s12010-014-0915-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 04/09/2014] [Indexed: 11/25/2022]
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12
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Studies on a New Binuclear Tungsten(IV)-pterin Complex Showing Reactivity Towards Trimethylamine N-oxide. TRANSIT METAL CHEM 2014. [DOI: 10.1007/s11243-005-5635-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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14
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Wang D. Redox chemistry of molybdenum in natural waters and its involvement in biological evolution. Front Microbiol 2012; 3:427. [PMID: 23267355 PMCID: PMC3528336 DOI: 10.3389/fmicb.2012.00427] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2012] [Accepted: 12/03/2012] [Indexed: 11/13/2022] Open
Abstract
The transition element molybdenum (Mo) possesses diverse valances (+II to +VI), and is involved in forming cofactors in more than 60 enzymes in biology. Redox switching of the element in these enzymes catalyzes a series of metabolic reactions in both prokaryotes and eukaryotes, and the element therefore plays a fundamental role in the global carbon, nitrogen, and sulfur cycling. In the present oxygenated waters, oxidized Mo(VI) predominates thermodynamically, whilst reduced Mo species are mainly confined within specific niches including cytoplasm. Only recently has the reduced Mo(V) been separated from Mo(VI) in sulfidic mats and even in some reducing waters. Given the presence of reduced Mo(V) in contemporary anaerobic habitats, it seems that reduced Mo species were present in the ancient reducing ocean (probably under both ferruginous and sulfidic conditions), prompting the involvement of Mo in enzymes including nitrogenase and nitrate reductase. During the global transition to oxic conditions, reduced Mo species were constrained to specific anaerobic habitats, and efficient uptake systems of oxidized Mo(VI) became a selective advantage for current prokaryotic and eukaryotic cells. Some prokaryotes are still able to directly utilize reduced Mo if any exists in ambient environments. In total, this mini-review describes the redox chemistry and biogeochemistry of Mo over the Earth’s history.
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Affiliation(s)
- Deli Wang
- State Key Laboratory of Marine Environmental Science, Xiamen University Xiamen, China
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15
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Witthoff S, Eggeling L, Bott M, Polen T. Corynebacterium glutamicum harbours a molybdenum cofactor-dependent formate dehydrogenase which alleviates growth inhibition in the presence of formate. Microbiology (Reading) 2012; 158:2428-2439. [DOI: 10.1099/mic.0.059196-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Sabrina Witthoff
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Lothar Eggeling
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Michael Bott
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Tino Polen
- Institut für Bio- und Geowissenschaften, IBG-1: Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
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16
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Ali SA, Soliman AA, Marei AH, Nassar DH. Synthesis and characterization of new chromium, molybdenum and tungsten complexes of 2-[2-(methylaminoethyl)] pyridine. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2012; 94:164-168. [PMID: 22513171 DOI: 10.1016/j.saa.2012.03.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/03/2012] [Accepted: 03/09/2012] [Indexed: 05/31/2023]
Abstract
A green chemistry route of synthesis using direct sunlight irradiation for the reactions of [M(CO)(6)] M=Cr, Mo or W with 2-[2-(methylaminoethyl)] pyridine (maepy) in THF. The reactions resulted in the formation of the oxo complex [Cr(2)(O)(4)(maepy)(2)] (1) and the tetracarbonyl complexes [Mo(CO)(4)(maepy)] (2) and [W(CO)(4)(maepy)] (3). The prepared complexes were characterized by elemental analysis, IR, NMR, mass spectrometry and magnetic measurement. The complexes (1-3) were further investigated by thermogravimetric technique (TG). The biological activity of maepy and complexes as antibacterial and antifungal reagents have been investigated.
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Affiliation(s)
- Saadia A Ali
- Chemistry Department, University College for Girls, Ain Shams University, Cairo, Egypt
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17
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Soliman AA, Ali SA, Marei AH, Nassar DH. Synthesis, characterization and biological activities of some new chromium molybdenum and tungsten complexes with 2,6-diaminopyridine. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2012; 89:329-332. [PMID: 22286054 DOI: 10.1016/j.saa.2011.12.061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 12/11/2011] [Accepted: 12/21/2011] [Indexed: 05/31/2023]
Abstract
The reactions of [M(CO)6], M=Cr, Mo, W with 2,6-diaminopyridine (dap) in ethanol was carried out under sun light and microwave irradiation routes of synthesis and compared with the traditional thermal reflux method. All routes resulted in the formation of the binuclear oxo complexes with the general formulas [M2(O)4(dap)2]. The prepared complexes were characterized using elemental analysis, IR, 1HNMR, mass spectrometry and magnetic measurement. The biological activity of dap and its complexes as antibacterial and antifungal reagents have been screened.
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Affiliation(s)
- Ahmed A Soliman
- Department of Chemistry, Faculty of Science, Cairo University, 12613 Giza, Egypt.
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18
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Charged dioxomolybdenum(VI) complexes with pyridoxal thiosemicarbazone ligands as molybdenum(V) precursors in oxygen atom transfer process and epoxidation (pre)catalysts. Polyhedron 2012. [DOI: 10.1016/j.poly.2011.12.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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19
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Liao RZ, Yu JG, Himo F. Tungsten-dependent formaldehyde ferredoxin oxidoreductase: Reaction mechanism from quantum chemical calculations. J Inorg Biochem 2011; 105:927-36. [DOI: 10.1016/j.jinorgbio.2011.03.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 03/25/2011] [Accepted: 03/28/2011] [Indexed: 11/30/2022]
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20
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Antony S, Bayse CA. Theoretical Studies of Models of the Active Site of the Tungstoenzyme Acetylene Hydratase. Organometallics 2009. [DOI: 10.1021/om900230x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sonia Antony
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529
| | - Craig A. Bayse
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529
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21
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Bayse CA. Density-functional theory models of xanthine oxidoreductase activity: comparison of substrate tautomerization and protonation. Dalton Trans 2009:2306-14. [DOI: 10.1039/b821878a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Jormakka M, Yokoyama K, Yano T, Tamakoshi M, Akimoto S, Shimamura T, Curmi P, Iwata S. Molecular mechanism of energy conservation in polysulfide respiration. Nat Struct Mol Biol 2008; 15:730-7. [PMID: 18536726 DOI: 10.1038/nsmb.1434] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2008] [Accepted: 04/23/2008] [Indexed: 11/09/2022]
Abstract
Bacterial polysulfide reductase (PsrABC) is an integral membrane protein complex responsible for quinone-coupled reduction of polysulfide, a process important in extreme environments such as deep-sea vents and hot springs. We determined the structure of polysulfide reductase from Thermus thermophilus at 2.4-A resolution, revealing how the PsrA subunit recognizes and reduces its unique polyanionic substrate. The integral membrane subunit PsrC was characterized using the natural substrate menaquinone-7 and inhibitors, providing a comprehensive representation of a quinone binding site and revealing the presence of a water-filled cavity connecting the quinone binding site on the periplasmic side to the cytoplasm. These results suggest that polysulfide reductase could be a key energy-conserving enzyme of the T. thermophilus respiratory chain, using polysulfide as the terminal electron acceptor and pumping protons across the membrane via a previously unknown mechanism.
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Affiliation(s)
- Mika Jormakka
- Department of Biophysics, University of New South Wales, Barker Street, Sydney, New South Wales 2052, Australia.
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23
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Andreesen JR, Makdessi K. Tungsten, the surprisingly positively acting heavy metal element for prokaryotes. Ann N Y Acad Sci 2007; 1125:215-29. [PMID: 18096847 DOI: 10.1196/annals.1419.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The history and changing function of tungsten as the heaviest element in biological systems is given. It starts from an inhibitory element/anion, especially for the iron molybdenum-cofactor (FeMoCo)-containing enzyme nitrogenase involved in dinitrogen fixation, as well as for the many "metal binding pterin" (MPT)-, also known as tricyclic pyranopterin- containing classic molybdoenzymes, such as the sulfite oxidase and the xanthine dehydrogenase family of enzymes. They are generally involved in the transformation of a variety of carbon-, nitrogen- and sulfur-containing compounds. But tungstate can serve as a potential positively acting element for some enzymes of the dimethyl sulfoxide (DMSO) reductase family, especially for CO(2)-reducing formate dehydrogenases (FDHs), formylmethanofuran dehydrogenases and acetylene hydratase (catalyzing only an addition of water, but no redox reaction). Tungsten even becomes an essential element for nearly all enzymes of the aldehyde oxidoreductase (AOR) family. Due to the close chemical and physical similarities between molybdate and tungstate, the latter was thought to be only unselectively cotransported or cometabolized with other tetrahedral anions, such as molybdate and also sulfate. However, it has now become clear that it can also be very selectively transported compared to molybdate into some prokaryotic cells by two very selective ABC-type of transporters that contain a binding protein TupA or WtpA. Both proteins exhibit an extremely high affinity for tungstate (K(D) < 1 nM) and can even discriminate between tungstate and molybdate. By that process, tungsten finally becomes selectively incorporated into the few enzymes noted above.
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Affiliation(s)
- Jan R Andreesen
- Institute of Biology/Microbiology, Martin-Luther-University Halle-Wittenberg, Halle, Germany.
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24
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Wallace D, Gibson LT, Reglinski J, Spicer MD. [Mo(TmMe)(O)2Cl]: An Alternative Functional Model of Sulfite Oxidase. Inorg Chem 2007; 46:3804-6. [PMID: 17419621 DOI: 10.1021/ic700468m] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The hydrotris(methimazolyl)borate anion (TmMe) has been used to synthesize an alternative functional model ([Mo(TmMe)(O)2Cl]) of the metalloenzyme sulfite oxidase. It has been shown that the complex undergoes oxygen atom transfer chemistry and that it performs the primary function of the enzyme, sulfite oxidation. A method using ion chromatography has been developed to definitively prove that sulfite is oxidized to sulfate. Employment of a soft tripodal ligand has allowed us to tune the redox potentials of our complex so that they are significantly closer to those reported for sulfite oxidase.
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Affiliation(s)
- Dawn Wallace
- Department of Pure & Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, UK.
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25
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McNaughton RL, Mondal S, Nemykin VN, Basu P, Kirk ML. Oxomolybdenum tetrathiolates with sterically encumbering ligands: modeling the effect of a protein matrix on electronic structure and reduction potentials. Inorg Chem 2006; 44:8216-22. [PMID: 16270958 DOI: 10.1021/ic0482281] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The effect of sterically encumbering ligands on the electronic structure of oxomolybdenum tetrathiolate complexes was determined using a combination of electronic absorption and magnetic circular dichroism spectroscopies, complimented by DFT bonding calculations, to understand geometric and electronic structure contributions to reduction potentials. These complexes are rudimentary models for a redox-active metalloenzyme active site in a protein matrix and allow for detailed spectroscopic probing of specific oxomolybdenum-thiolate interactions that are directly relevant to Mo-S(cysteine) bonding in pyranopterin molybdenum enzymes. Data are presented for three para-substituted oxomolybdenum tetrathiolate complexes ([PPh4][MoO(p-SPhCONHCH3)4], [PPh4][MoO(p-SPhCONHC(CH2O(CH2)2CN)3)4], and [PPh4][MoO(p-SPhCONHC(CH2O(CH2)2COOCH2CH3)3)4]). The Mo(V/IV) reduction potentials of the complexes in DMF are -1213, -1251, and -1247 mV, respectively. The remarkably similar electronic absorption and magnetic circular dichroism spectra of these complexes establish that the observed reduction potential differences are not a result of significant changes in the electronic structure of the [MoOS4]- cores as a function of the larger ligand size. We provide evidence that these reduction potential differences result from the driving force for a substantial reorganization of the O-Mo-S-C dihedral angle upon reduction, which decreases electron donation from the thiolate sulfurs to the reduced molybdenum center. The energy barrier to favorable O-Mo-S-C geometries results in a reorganizational energy increase, relative to [MoO(SPh)4](-/2-), that correlates with ligand size. The inherent flexible nature of oxomolybdenum-thiolate bonds indicate that thiolate ligand geometry, which controls Mo-S covalency, could affect the redox processes of monooxomolybdenum centers in pyranopterin molybdenum enzymes.
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Affiliation(s)
- Rebecca L McNaughton
- Department of Chemistry, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, USA
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26
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Abstract
Unlike monooxygenases, molybdenum-containing hydroxylases catalyze the hydroxylation of carbon centers using oxygen derived ultimately from water, rather than O(2), as the source of the oxygen atom incorporated into the product, and do not require an external source of reducing equivalents. The mechanism by which this interesting chemistry takes place has been the subject of investigation for some time, and in the last several years the chemical course of the reaction has become increasingly well understood. The present minireview summarizes recent mechanistic and structure/function studies of members of this large and growing family of enzymes.
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Affiliation(s)
- Russ Hille
- Department of Molecular and Cellular Biochemistry, The Ohio State University, 333 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA.
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27
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Schrader N, Fischer K, Theis K, Mendel RR, Schwarz G, Kisker C. The crystal structure of plant sulfite oxidase provides insights into sulfite oxidation in plants and animals. Structure 2004; 11:1251-63. [PMID: 14527393 DOI: 10.1016/j.str.2003.09.001] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The molybdenum cofactor (Moco) containing sulfite oxidase (SO) from Arabidopsis thaliana has recently been identified and biochemically characterized. The enzyme is found in peroxisomes and believed to detoxify excess sulfite that is produced during sulfur assimilation, or due to air pollution. Plant SO (PSO) is homodimeric and homologous to animal SO, but contains only a single Moco domain without an additional redox center. Here, we present the first crystal structure of a plant Moco enzyme, the apo-state of Arabidopsis SO at 2.6 A resolution. The overall fold and coordination of the Moco are similar to chicken SO (CSO). Comparisons of conserved surface residues and the charge distribution in PSO and CSO reveal major differences near the entrance to both active sites reflecting different electron acceptors. Arg374 has been identified as an important substrate binding residue due to its conformational change when compared to the sulfate bound structure of CSO.
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Affiliation(s)
- Nils Schrader
- Department of Pharmacological Sciences, Center for Structural Biology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA
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28
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Otero A, Fernández-Baeza J, Antiñolo A, Tejeda J, Lara-Sánchez A. Heteroscorpionate ligands based on bis(pyrazol-1-yl)methane: design and coordination chemistry. Dalton Trans 2004:1499-510. [PMID: 15252594 DOI: 10.1039/b401425a] [Citation(s) in RCA: 204] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Scorpionates represent one of the most versatile types of tridentate ligand that can coordinate to a wide variety of elements, e.g. from early to late transition metals, and the coordination chemistry of these systems has developed greatly in recent years. This Perspective gives an account of studies on the following aspects: (1) the preparative methods for a new class of heteroscorpionate [RR'C(pz)2] ligand derived from bis(pyrazol-1-yl)methane and (2) the description of metal complexes containing these ligands, examples of which incorporate a range of different metals from the Periodic Table.
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Affiliation(s)
- A Otero
- Departamento de Quimica Inorganica, Organica y Bioquimica, Universidad de Castilla-La Mancha, 13071-Ciudad Real, Spain.
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29
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Laska S, Lottspeich F, Kletzin A. Membrane-bound hydrogenase and sulfur reductase of the hyperthermophilic and acidophilic archaeon Acidianus ambivalens. MICROBIOLOGY (READING, ENGLAND) 2003; 149:2357-2371. [PMID: 12949162 DOI: 10.1099/mic.0.26455-0] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A sulfur reductase (SR) and a hydrogenase were purified from solubilized membrane fractions of anaerobically grown cells of the sulfur-dependent archaeon Acidianus ambivalens and the corresponding genes were sequenced. The SR reduced elemental sulfur with hydrogen as electron donor [45 U (mg protein)(-1)] in the presence of hydrogenase and either 2,3-dimethylnaphthoquinone (DMN) or cytochrome c in the enzyme assay. The SR could not be separated from the hydrogenase during purification without loss of activity, whereas the hydrogenase could be separated from the SR. The specific activity of the hydrogenase was 170 U (mg protein)(-1) with methyl viologen and 833 U (mg protein)(-1) with DMN as electron acceptors. Both holoenzymes showed molecular masses of 250 kDa. In SDS gels of active fractions, protein bands with apparent masses of 110 (SreA), 66 (HynL), 41 (HynS) and 29 kDa were present. Enriched hydrogenase fractions contained 14 micro mol Fe and 2 micromol Ni (g protein)(-1); in addition, 2.5 micromol Mo (g protein)(-1) was found in the membrane fraction. Two overlapping genomic cosmid clones were sequenced, encoding a five-gene SR cluster (sre) including the 110 kDa subunit gene (sreA), and a 12-gene hydrogenase cluster (hyn) including the large and small subunit genes and genes encoding proteins required for the maturation of NiFe hydrogenases. A phylogenetic analysis of the SR amino acid sequence revealed that the protein belonged to the DMSO reductase family of molybdoenzymes and that the family showed a novel clustering. A model of sulfur respiration in Acidianus developed from the biochemical results and the data of the amino acid sequence comparisons is discussed.
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Affiliation(s)
- Simone Laska
- Institute of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
| | - Friedrich Lottspeich
- Institute of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
| | - Arnulf Kletzin
- Institute of Microbiology and Genetics, Darmstadt University of Technology, Schnittspahnstrasse 10, 64287 Darmstadt, Germany
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30
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Veige AS, Slaughter LM, Lobkovsky EB, Wolczanski PT, Matsunaga N, Decker SA, Cundari TR. Symmetry and Geometry Considerations of Atom Transfer: Deoxygenation of (silox)3WNO and R3PO (R = Me, Ph, tBu) by (silox)3M (M = V, NbL (L = PMe3, 4-Picoline), Ta; silox = tBu3SiO). Inorg Chem 2003; 42:6204-24. [PMID: 14514296 DOI: 10.1021/ic0300114] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Deoxygenations of (silox)(3)WNO (12) and R(3)PO (R = Me, Ph, (t)Bu) by M(silox)(3) (1-M; M = V, NbL (L = PMe(3), 4-picoline), Ta; silox = (t)Bu(3)SiO) reflect the consequences of electronic effects enforced by a limiting steric environment. 1-Ta rapidly deoxygenated R(3)PO (23 degrees C; R = Me (DeltaG degrees (rxn)(calcd) = -47 kcal/mol), Ph) but not (t)Bu(3)PO (85 degrees, >2 days), and cyclometalation competed with deoxygenation of 12 to (silox)(3)WN (11) and (silox)(3)TaO (3-Ta; DeltaG degrees (rxn)(calcd) = -100 kcal/mol). 1-V deoxygenated 12 slowly and formed stable adducts (silox)(3)V-OPR(3) (3-OPR(3)) with OPR(3). 1-Nb(4-picoline) (S = 0) and 1-NbPMe(3) (S = 1) deoxygenated R(3)PO (23 degrees C; R = Me (DeltaG degrees (rxn)(calcd from 1-Nb) = -47 kcal/mol), Ph) rapidly and 12 slowly (DeltaG degrees (rxn)(calcd) = -100 kcal/mol), and failed to deoxygenate (t)Bu(3)PO. Access to a triplet state is critical for substrate (EO) binding, and the S --> T barrier of approximately 17 kcal/mol (calcd) hinders deoxygenations by 1-Ta, while 1-V (S = 1) and 1-Nb (S --> T barrier approximately 2 kcal/mol) are competent. Once binding occurs, significant mixing with an (1)A(1) excited state derived from population of a sigma-orbital is needed to ensure a low-energy intersystem crossing of the (3)A(2) (reactant) and (1)A(1) (product) states. Correlation of a reactant sigma-orbital with a product sigma-orbital is required, and the greater the degree of bending in the (silox)(3)M-O-E angle, the more mixing energetically lowers the intersystem crossing point. The inability of substrates EO = 12 and (t)Bu(3)PO to attain a bent 90 degree angle M-O-E due to sterics explains their slow or negligible deoxygenations. Syntheses of relevant compounds and ramifications of the results are discussed. X-ray structural details are provided for 3-OPMe(3) (90 degree angle V-O-P = 157.61(9) degrees), 3-OP(t)Bu(3) ( 90 degree angle V-O-P = 180 degrees ), 1-NbPMe(3), and (silox)(3)ClWO (9).
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Affiliation(s)
- Adam S Veige
- Department of Chemistry & Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853, USA
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31
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Abstract
Advances in bioinorganic chemistry since the 1970s have been driven by three factors: rapid determination of high-resolution structures of proteins and other biomolecules, utilization of powerful spectroscopic tools for studies of both structures and dynamics, and the widespread use of macromolecular engineering to create new biologically relevant structures. Today, very large molecules can be manipulated at will, with the result that certain proteins and nucleic acids themselves have become versatile model systems for elucidating biological function.
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Affiliation(s)
- Harry B Gray
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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32
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Abstract
Quite extraordinarily molybdenum is an essential element in life for the uptake of nitrogen from both nitrogen gas and nitrate, yet it is a relatively rare heavy trace element. It also functions in a few extremely important oxygen-atom transfer reactions at low redox potential. This review poses the question "Why does life depend upon molybdenum?" The answer has to be based upon the availability of the element and on chemical superiority in carrying out the essential tasks. We illustrate here the peculiarities of molybdenum chemistry and how they have become part of certain enzymes. The uptake and incorporation of molybdenum are dependent on its availability, selective pumps, and carriers (chaperones), but 4.5 x 10(9) years ago molybdenum was not available when both tungsten and vanadium or even iron were possibly used in its place. While these possibilities are explored, they leave many unanswered questions concerning the selection today of molybdenum.
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Affiliation(s)
- R J P Williams
- Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom.
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33
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Abstract
[reaction--see text] Nitric oxide (NO) is an important biological messenger molecule. Nitrates, including nitroglycerin (GTN), are clinically important vasodilators believed to be biotransformed in vivo to NO, a 3e(-) reduction. Molybdenum hydrotris-(3,5-dimethyl-1-pyrazolyl) borate complex (MoTPB) was shown to be an efficient catalyst of GTN degradation, with triphenylphosphine (Ph(3)P) acting as reducing cofactor, producing significant amounts of NO. MoTPB/Ph(3)P is an excellent enzyme model system, showing the feasibility of nitrate biotransformation mediated by a molybdoenzyme.
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Affiliation(s)
- J Murray
- Department of Chemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada
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34
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Gutzke G, Fischer B, Mendel RR, Schwarz G. Thiocarboxylation of molybdopterin synthase provides evidence for the mechanism of dithiolene formation in metal-binding pterins. J Biol Chem 2001; 276:36268-74. [PMID: 11459846 DOI: 10.1074/jbc.m105321200] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Molybdopterin (MPT) is a pyranopterin with a unique dithiolene group coordinating molybdenum (Mo) or tungsten (W) in all Mo- and W-enzymes except nitrogenase. In Escherichia coli, MPT is formed by incorporation of two sulfur atoms into precursor Z, which is catalyzed by MPT synthase. The recently solved crystal structure of MPT synthase (Rudolph, M. J., Wuebbens, M. M., Rajagopalan, K. V., and Schindelin, H. (2000) Nat. Struct. Biol. 8, 42-46) shows the heterotetrameric nature of the enzyme that is composed of two small (MoaD) and two large subunits (MoaE). According to sequence and structural similarities among MoaD, ubiquitin, and ThiS, a thiocarboxylation of the C terminus of MoaD is proposed that would serve as the source of sulfur that is transferred to precursor Z. Here, we describe the in vitro generation of carboxylated and thiocarboxylated MoaD. Both forms of MoaD are monomeric and are able to form a heterotetrameric complex after coincubation in equimolar ratios with MoaE. Only the thiocarboxylated MPT synthase complex was found to be able to convert precursor Z in vitro to MPT. Slight but significant differences between the carboxylated and the thiocarboxylated MPT synthase can be seen using size exclusion chromatography. A two-step reaction of MPT synthesis is proposed where the dithiolene is generated by two thiocarboxylates derived from a single tetrameric MPT synthase.
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Affiliation(s)
- G Gutzke
- Botanical Institute, Technical University of Braunschweig, 38023 Braunschweig, Germany
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35
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Arias J, Newlands CR, Abu-Omar MM. Kinetics and mechanisms of catalytic oxygen atom transfer with oxorhenium(V) oxazoline complexes. Inorg Chem 2001; 40:2185-92. [PMID: 11304165 DOI: 10.1021/ic000917z] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The rhenium(V) monooxo complexes (hoz)2Re(O)Cl (1) and [(hoz)2Re(O)(OH2)][OTf] (2) have been synthesized and fully characterized (hoz = 2-(2'-hydroxyphenyl)-2-oxazoline). A single-crystal X-ray structure of 2 has been solved: space group = P1, a = 13.61(2) A, b = 14.76(2) A, c = 11.871(14) A, alpha = 93.69(4) degrees, beta = 99.43(4) degrees, gamma = 108.44(4) degrees, Z = 4; the structure was refined to final residuals R = 0.0455 and Rw = 0.1055. 1 and 2 catalyze oxygen atom transfer from aryl sulfoxides to alkyl sulfides and oxygen-scrambling between sulfoxides to yield sulfone and sulfide. Superior catalytic activity has been observed for 2 due to the availability of a coordination site on the rhenium. The active form of the catalyst is a dioxo rhenium(VII) intermediate, [Re(O)2(hoz)2]+ (3). In the presence of sulfide, 3 is rapidly reduced to [Re(O)(hoz)2]+ with sulfoxide as the sole organic product. The transition state is very sensitive to electronic influences. A Hammett correlation plot with para-substituted thioanisole derivatives gave a reaction constant rho of -4.6 +/- 0.4, in agreement with an electrophilic oxygen transfer from rhenium. The catalytic reaction features inhibition by sulfides at high concentrations. The equilibrium constants for sulfide binding to complex 2 (cause of inhibition), K2 (L x mol(-1)), were determined for a few sulfides: Me2S (22 +/- 3), Et2S (14 +/- 2), and tBu2S (8 +/- 2). Thermodynamic data, obtained from equilibrium measurements in solution, show that the S=O bond in alkyl sulfoxides is stronger than in aryl sulfoxides. The Re=O bond strength in 3 was estimated to be about 20 kcal x mol(-1). The high activity and oxygen electrophilicity of complex 3 are discussed and related to analogous molybdenum systems.
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Affiliation(s)
- J Arias
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, California 90095-1569, USA
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36
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Functional model of oxomolybdoenzymes: Synthesis and characterization of a molybdenum complex with sulphur and pterin ligands exhibiting saturation kinetics with pyridine N-oxide. J CHEM SCI 2001. [DOI: 10.1007/bf02704179] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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37
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Anderson LA, McNairn E, Lubke T, Pau RN, Boxer DH, Leubke T. ModE-dependent molybdate regulation of the molybdenum cofactor operon moa in Escherichia coli. J Bacteriol 2000; 182:7035-43. [PMID: 11092866 PMCID: PMC94831 DOI: 10.1128/jb.182.24.7035-7043.2000] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of the moa locus, which encodes enzymes required for molybdopterin biosynthesis, is enhanced under anaerobiosis but repressed when the bacterium is able to synthesize active molybdenum cofactor. In addition, moa expression exhibits a strong requirement for molybdate. The molybdate enhancement of moa transcription is fully dependent upon the molybdate-binding protein, ModE, which also mediates molybdate repression of the mod operon encoding the high-affinity molybdate uptake system. Due to the repression of moa in molybdenum cofactor-sufficient strains, the positive molybdate regulation of moa is revealed only in strains unable to make the active cofactor. Transcription of moa is controlled at two sigma-70-type promoters immediately upstream of the moaA gene. Deletion mutations covering the region upstream of moaA have allowed each of the promoters to be studied in isolation. The distal promoter is the site of the anaerobic enhancement which is Fnr-dependent. The molybdate induction of moa is exerted at the proximal promoter. Molybdate-ModE binds adjacent to the -35 region of this promoter, acting as a direct positive regulator of moa. The molybdenum cofactor repression also appears to act at the proximal transcriptional start site, but the mechanism remains to be established. Tungstate in the growth medium affects moa expression in two ways. Firstly, it can act as a functional molybdate analogue for the ModE-mediated regulation. Secondly, tungstate brings about the loss of the molybdenum cofactor repression of moa. It is proposed that the tungsten derivative of the molybdenum cofactor, which is known to be formed under such conditions, is ineffective in bringing about repression of moa. The complex control of moa is discussed in relation to the synthesis of molybdoenzymes in the bacterium.
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Affiliation(s)
- L A Anderson
- Department of Biochemistry, University of Dundee, Dundee DD1 5EH, Scotland
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38
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Thapper A, Lorber C, Fryxelius J, Behrens A, Nordlander E. Synthesis and reactivity studies of model complexes for molybdopterin-dependent enzymes. J Inorg Biochem 2000; 79:67-74. [PMID: 10830849 DOI: 10.1016/s0162-0134(00)00010-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The molybdenum cofactor (Moco)-containing enzymes are divided into three classes that are named after prototypical members of each family, viz. sulfite oxidase, DMSO reductase and xanthine oxidase. Functional or structural models have been prepared for these three prototypical enzymes: (i) The complex [MoO2(mnt)2]2- (mnt2- = 1,2-dicyanoethylenedithiolate) has been found to be able to oxidize hydrogen sulfite to HSO4- and is thus a functional model of sulfite oxidase. Kinetic and computational studies indicate that the reaction proceeds via attack of the substrate at one of the oxo ligands of the complex, rather than at the metal. (ii) The coordination geometries of the mono-oxo [Mo(VI)(O-Ser)(S2)2] entity (S2 = dithiolene moiety of molybdopterin) found in the crystal structure of R. sphaeroides DMSO reductase and the corresponding des-oxo Mo(IV) unit have been reproduced in the complexes [M(VI)O(OSiR3)(bdt)2] and [M(VI)O(OSiR3)(bdt)2] (M = Mo,W; bdt = benzene dithiolate). (iii) A facile route has been developed for the preparation of complexes containing a cis-Mo(VI)OS molybdenum oxo, sulfido moiety similar to that detected in the oxidized form of xanthine oxidase.
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Affiliation(s)
- A Thapper
- Chemical Center, Lund University, Sweden
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