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Maia LB. Bringing Nitric Oxide to the Molybdenum World-A Personal Perspective. Molecules 2023; 28:5819. [PMID: 37570788 PMCID: PMC10420851 DOI: 10.3390/molecules28155819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 07/29/2023] [Accepted: 07/30/2023] [Indexed: 08/13/2023] Open
Abstract
Molybdenum-containing enzymes of the xanthine oxidase (XO) family are well known to catalyse oxygen atom transfer reactions, with the great majority of the characterised enzymes catalysing the insertion of an oxygen atom into the substrate. Although some family members are known to catalyse the "reverse" reaction, the capability to abstract an oxygen atom from the substrate molecule is not generally recognised for these enzymes. Hence, it was with surprise and scepticism that the "molybdenum community" noticed the reports on the mammalian XO capability to catalyse the oxygen atom abstraction of nitrite to form nitric oxide (NO). The lack of precedent for a molybdenum- (or tungsten) containing nitrite reductase on the nitrogen biogeochemical cycle contributed also to the scepticism. It took several kinetic, spectroscopic and mechanistic studies on enzymes of the XO family and also of sulfite oxidase and DMSO reductase families to finally have wide recognition of the molybdoenzymes' ability to form NO from nitrite. Herein, integrated in a collection of "personal views" edited by Professor Ralf Mendel, is an overview of my personal journey on the XO and aldehyde oxidase-catalysed nitrite reduction to NO. The main research findings and the path followed to establish XO and AO as competent nitrite reductases are reviewed. The evidence suggesting that these enzymes are probable players of the mammalian NO metabolism is also discussed.
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Affiliation(s)
- Luisa B Maia
- LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology (FCT NOVA), 2829-516 Caparica, Portugal
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2
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Kirk ML, Hille R. Spectroscopic Studies of Mononuclear Molybdenum Enzyme Centers. Molecules 2022; 27:molecules27154802. [PMID: 35956757 PMCID: PMC9370002 DOI: 10.3390/molecules27154802] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 06/26/2022] [Accepted: 06/29/2022] [Indexed: 02/06/2023] Open
Abstract
A concise review is provided of the contributions that various spectroscopic methods have made to our understanding of the physical and electronic structures of mononuclear molybdenum enzymes. Contributions to our understanding of the structure and function of each of the major families of these enzymes is considered, providing a perspective on how spectroscopy has impacted the field.
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Affiliation(s)
- Martin L. Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA
- Correspondence: (M.L.K.); (R.H.)
| | - Russ Hille
- Department of Biochemistry, Boyce Hall 1463, University of California, Riverside, CA 82521, USA
- Correspondence: (M.L.K.); (R.H.)
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3
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Maiti M, Thakurta S, Pilet G, Bauzá A, Frontera A. Two new hydrogen-bonded supramolecular dioxo-molybdenum(VI) complexes based on acetyl-hydrazone ligands: Synthesis, crystal structure and DFT studies. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2020.129346] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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4
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Ehweiner MA, Wiedemaier F, Belaj F, Mösch-Zanetti NC. Oxygen Atom Transfer Reactivity of Molybdenum(VI) Complexes Employing Pyrimidine- and Pyridine-2-thiolate Ligands. Inorg Chem 2020; 59:14577-14593. [PMID: 32951421 DOI: 10.1021/acs.inorgchem.0c02412] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Four dioxidomolybdenum(VI) complexes of the general structure [MoO2L2] employing the S,N-bidentate ligands pyrimidine-2-thiolate (PymS, 1), pyridine-2-thiolate (PyS, 2), 4-methylpyridine-2-thiolate (4-MePyS, 3) and 6-methylpyridine-2-thiolate (6-MePyS, 4) were synthesized and characterized by spectroscopic means and single-crystal X-ray diffraction analysis (2-4). Complexes 1-4 were reacted with PPh3 and PMe3, respectively, to investigate their oxygen atom transfer (OAT) reactivity and catalytic applicability. Reduction with PPh3 leads to symmetric molybdenum(V) dimers of the general structure [Mo2O3L4] (6-9). Kinetic studies showed that the OAT from [MoO2L2] to PPh3 is 5 times faster for the PymS system than for the PyS and 4-MePyS systems. The reaction of complexes 1-3 with PMe3 gives stable molybdenum(IV) complexes of the structure [MoOL2(PMe3)2] (10-12), while reduction of [MoO2(6-MePyS)2] (4) yields [MoO(6-MePyS)2(PMe3)] (13) with only one PMe3 coordinated to the metal center. The activity of complexes 1-4 in catalytic OAT reactions involving Me2SO and Ph2SO as oxygen donors and PPh3 as an oxygen acceptor has been investigated to assess the influence of the varied ligand frameworks on the OAT reaction rates. It was found that [MoO2(PymS)2] (1) and [MoO2(6-MePyS)2] (4) are similarly efficient catalysts, while complexes 2 and 3 are only moderately active. In the catalytic oxidation of PMe3 with Me2SO, complex 4 is the only efficient catalyst. Complexes 1-4 were also found to catalytically reduce NO3- with PPh3, although their reactivity is inhibited by further reduced species such as NO, as exemplified by the formation of the nitrosyl complex [Mo(NO)(PymS)3] (14), which was identified by single-crystal X-ray diffraction analysis. Computed ΔG⧧ values for the very first step of the OAT were found to be lower for complexes 1 and 4 than for 2 and 3, explaining the difference in catalytic reactivity between the two pairs and revealing the requirement for an electron-deficient ligand system.
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Affiliation(s)
- Madeleine A Ehweiner
- Institute of Chemistry, Inorganic Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
| | - Fabian Wiedemaier
- Institute of Chemistry, Physical and Theoretical Chemistry, University of Graz, Heinrichstrasse 28, 8010 Graz, Austria
| | - Ferdinand Belaj
- Institute of Chemistry, Inorganic Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
| | - Nadia C Mösch-Zanetti
- Institute of Chemistry, Inorganic Chemistry, University of Graz, Schubertstrasse 1, 8010 Graz, Austria
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5
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Microbial nanowires - Electron transport and the role of synthetic analogues. Acta Biomater 2018; 69:1-30. [PMID: 29357319 DOI: 10.1016/j.actbio.2018.01.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 01/07/2018] [Accepted: 01/09/2018] [Indexed: 02/07/2023]
Abstract
Electron transfer is central to cellular life, from photosynthesis to respiration. In the case of anaerobic respiration, some microbes have extracellular appendages that can be utilised to transport electrons over great distances. Two model organisms heavily studied in this arena are Shewanella oneidensis and Geobacter sulfurreducens. There is some debate over how, in particular, the Geobacter sulfurreducens nanowires (formed from pilin nanofilaments) are capable of achieving the impressive feats of natural conductivity that they display. In this article, we outline the mechanisms of electron transfer through delocalised electron transport, quantum tunnelling, and hopping as they pertain to biomaterials. These are described along with existing examples of the different types of conductivity observed in natural systems such as DNA and proteins in order to provide context for understanding the complexities involved in studying the electron transport properties of these unique nanowires. We then introduce some synthetic analogues, made using peptides, which may assist in resolving this debate. Microbial nanowires and the synthetic analogues thereof are of particular interest, not just for biogeochemistry, but also for the exciting potential bioelectronic and clinical applications as covered in the final section of the review. STATEMENT OF SIGNIFICANCE Some microbes have extracellular appendages that transport electrons over vast distances in order to respire, such as the dissimilatory metal-reducing bacteria Geobacter sulfurreducens. There is significant debate over how G. sulfurreducens nanowires are capable of achieving the impressive feats of natural conductivity that they display: This mechanism is a fundamental scientific challenge, with important environmental and technological implications. Through outlining the techniques and outcomes of investigations into the mechanisms of such protein-based nanofibrils, we provide a platform for the general study of the electronic properties of biomaterials. The implications are broad-reaching, with fundamental investigations into electron transfer processes in natural and biomimetic materials underway. From these studies, applications in the medical, energy, and IT industries can be developed utilising bioelectronics.
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6
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Hasenaka Y, Okamura TA, Onitsuka K. Modeling of the hydrophobic microenvironment of water-soluble molybdoenzymes in an aqueous micellar solution. Dalton Trans 2016; 44:12618-22. [PMID: 26076318 DOI: 10.1039/c5dt01112d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A toluene-soluble molybdenum(vi) complex containing a bulky hydrophobic substituent, (Et4N)2[Mo(VI)O2{1,2-S2-3,6-(RCONH)2C6H2}2] (R = (4-(t)BuC6H4)3C), was dissolved in the hydrophobic core of a micelle in an aqueous medium and catalyzed the biomimetic reduction of an amine N-oxide by an NADH analog. The kinetic isotope effect of solvent water clearly indicates that water molecules are essential for catalysis and are involved in the rate-determining step.
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Affiliation(s)
- Yuki Hasenaka
- Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
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7
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Heinze K. Bioinspired functional analogs of the active site of molybdenum enzymes: Intermediates and mechanisms. Coord Chem Rev 2015. [DOI: 10.1016/j.ccr.2015.04.010] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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8
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Nitrite reduction by molybdoenzymes: a new class of nitric oxide-forming nitrite reductases. J Biol Inorg Chem 2015; 20:403-33. [DOI: 10.1007/s00775-014-1234-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/14/2014] [Indexed: 02/07/2023]
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9
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Sparacino-Watkins C, Stolz JF, Basu P. Nitrate and periplasmic nitrate reductases. Chem Soc Rev 2014; 43:676-706. [PMID: 24141308 DOI: 10.1039/c3cs60249d] [Citation(s) in RCA: 186] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types--periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed.
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10
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - James Hall
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
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11
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Seo J, Williard PG, Kim E. Deoxygenation of mono-oxo bis(dithiolene) Mo and W complexes by protonation. Inorg Chem 2013; 52:8706-12. [PMID: 23865493 DOI: 10.1021/ic4008747] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Protonation-assisted deoxygenation of a mono-oxo molybdenum center has been observed in many oxotransferases when the enzyme removes an oxo group to regenerate a substrate binding site. Such a reaction is reported here with discrete synthetic mono-oxo bis(dithiolene) molybdenum and tungsten complexes, the chemistry of which had been rarely studied because of the instability of the resulting deoxygenated products. An addition of tosylic acid to an acetonitrile solution of [Mo(IV)O(S2C2Ph2)2](2-) (1) and [W(IV)O(S2C2Ph2)2](2-) (2) results in the loss of oxide with a concomitant formation of novel deoxygenated complexes, [M(MeCN)2(S2C2Ph2)2] (M = Mo (3), W (4)), that have been isolated and characterized. Whereas protonation of 1 exclusively produces 3, two different reaction products can be generated from 2; an oxidized product, [WO(S2C2Ph2)2](-), is produced with 1 equiv of acid while a deoxygenated product, [W(MeCN)2(S2C2Ph2)2] (4), is generated with an excess amount of proton. Alternatively, complexes 3 and 4 can be obtained from photolysis of [Mo(CO)2(S2C2Ph2)2] (5) and [W(CO)2(S2C2Ph2)2] (6) in acetonitrile. A di- and a monosubstituted adducts of 3, [Mo(CO)2(S2C2Ph2)2] (5) and [Mo(PPh3)(MeCN)(S2C2Ph2)2] (7) are also reported.
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Affiliation(s)
- Junhyeok Seo
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
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12
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TAKJOO REZA, HASHEMZADEH ALIREZA, RUDBARI HADIAMIRI, NICOLÒ FRANCESCO. Copper(II) and molybdenum(VI) complexes with 5-bromosalicylaldehyde S-allylisothiosemicarbazone: Syntheses, characterizations and crystal structures. J COORD CHEM 2013. [DOI: 10.1080/00958972.2012.748191] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- REZA TAKJOO
- a Department of Chemistry , School of Sciences, Ferdowsi University of Mashhad , Mashhad , Iran
| | - ALIREZA HASHEMZADEH
- a Department of Chemistry , School of Sciences, Ferdowsi University of Mashhad , Mashhad , Iran
| | - HADI AMIRI RUDBARI
- b Dipartimento di Chimica Inorganica , Chimica Analitica e Chimica Fisica Università di Messina , Contrada Papardo , Messina , Italy
| | - FRANCESCO NICOLÒ
- b Dipartimento di Chimica Inorganica , Chimica Analitica e Chimica Fisica Università di Messina , Contrada Papardo , Messina , Italy
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13
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Basu P, Kail BW, Adams AK, Nemykin VN. Quantitation of the ligand effect in oxo-transfer reactions of dioxo-Mo(VI) trispyrazolyl borate complexes. Dalton Trans 2012; 42:3071-81. [PMID: 23212540 DOI: 10.1039/c2dt32349d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The oxygen atom transfer reactivity (OAT) of dioxo-Mo(VI) complexes of hydrotrispyrazolyl borate (hydrotris(3,5-dimethylpyrazolyl)borate, Tp(Me2); hydrotris(3-isopropylpyrazol-1-yl)borate, Tp(iPr)) with tertiary phosphines (PMe(3), PMe(2)Ph, PEt(3), PEt(2)Ph, PBu(n)(3), PMePh(2), or PEtPh(2)) has been investigated. In acetonitrile, these reactions proceed via the formation of a phosphoryl intermediate complex that undergoes a solvolysis reaction. We report the synthesis and characterization of several phosphoryl complexes. The rates of formation of phosphoryl complexes and their solvation were determined by spectrophotometry. The rates of the reactions and the properties of the phosphoryl species were investigated using the Quantitative Analysis of Ligand Effect (QALE) methodology. The results show that, at least in this system, the first step of the reaction is controlled primarily by the steric factor, and in the second step, both electronic and steric factors are important. We also analyzed the effect of ligands on the reaction rate i.e., Tp(Me2)vs. Tp(iPr).
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Affiliation(s)
- Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, PA 15228, USA.
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14
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Takjoo R, Ahmadi M, Akbari A, Rudbari HA, Nicolò F. Complexes with cis-MoO2 unit of new isothiosemicarbazone. J COORD CHEM 2012. [DOI: 10.1080/00958972.2012.709935] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Reza Takjoo
- a Department of Chemistry, School of Sciences , Ferdowsi University of Mashhad , 91775-1436 Mashhad , Iran
| | - Mehdi Ahmadi
- b Department of Chemistry , Payame Noor University (PNU) , 19395-4697 Tehran , Iran
| | - Alireza Akbari
- b Department of Chemistry , Payame Noor University (PNU) , 19395-4697 Tehran , Iran
| | - Hadi Amiri Rudbari
- c Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica , Università di Messina , Salita Sperone, 31 Contrada Papardo, 98166 Messina , Italy
| | - Francesco Nicolò
- c Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica , Università di Messina , Salita Sperone, 31 Contrada Papardo, 98166 Messina , Italy
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15
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Nitrite reduction by xanthine oxidase family enzymes: a new class of nitrite reductases. J Biol Inorg Chem 2010; 16:443-60. [DOI: 10.1007/s00775-010-0741-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 11/19/2010] [Indexed: 02/04/2023]
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16
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Active transition metal oxo and hydroxo moieties in nature's redox, enzymes and their synthetic models: Structure and reactivity relationships. Coord Chem Rev 2010. [DOI: 10.1016/j.ccr.2010.01.016] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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17
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Hernandez-Marin E, Ziegler T. A kinetic study of dimethyl sulfoxide reductase based on density functional theory. CAN J CHEM 2010. [DOI: 10.1139/v09-136] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We present a density functional theory study on the oxygen atom transfer (OAT) reaction of dimethyl sulfoxide (DMSO) with model complexes resembling a functional synthetic analogue of the molybdoenzyme DMSO reductase. The good agreement between our calculated Gibbs free energy profile and data derived from experimental kinetic parameters supports the reaction mechanisms of the oxygen atom transfer proposed in this study. When the mechanism involves the formation of a DMSO-bound intermediate, the calculations on the free energy surface provide valuable information that explains the origin of the apparent contradiction between the experimental findings and previous theoretical calculations with respect to the rate-limiting step of the reaction mechanism. The enzymatic mechanism of the OAT reaction is more complex than the mechanism of any synthetic analogue, mainly due to the formation of an enzyme-substrate adduct prior to the appearance of the substrate-bound intermediate. This study also presents a possible mechanism for the formation of such an adduct and the subsequent oxygen atom transfer. The mechanism involves a proton transfer to and from the substrate.
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Affiliation(s)
| | - Tom Ziegler
- Department of Chemistry, University of Calgary, 2500 University Drive, Calgary, AB T2N 1N4, Canada
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18
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Basu P, Kail BW, Young CG. Influence of the oxygen atom acceptor on the reaction coordinate and mechanism of oxygen atom transfer from the dioxo-Mo(VI) complex, Tp(iPr)MoO(2)(OPh), to tertiary phosphines. Inorg Chem 2010; 49:4895-900. [PMID: 20433155 PMCID: PMC2897133 DOI: 10.1021/ic902500h] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The oxygen atom transfer reactivity of the dioxo-Mo(VI) complex, Tp(iPr)MoO(2)(OPh) (Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate), with a range of tertiary phosphines (PMe(3), PMe(2)Ph, PEt(3), PBu(n)(3), PEt(2)Ph, PEtPh(2), and PMePh(2)) has been investigated. The first step in all the reactions follows a second-order rate law indicative of an associative transition state, consistent with nucleophilic attack by the phosphine on an oxo ligand, namely, Tp(iPr)MoO(2)(OPh) + PR(3) --> Tp(iPr)MoO(OPh)(OPR(3)). The calculated free energy of activation for the formation of the OPMe(3) intermediate (Chem. Eur. J. 2006, 12, 7501) is in excellent agreement with the experimental DeltaG() value reported here. The second step of the reaction, that is, the exchange of the coordinated phosphine oxide by acetonitrile, Tp(iPr)MoO(OPh)(OPR(3)) + MeCN --> Tp(iPr)MoO(OPh)(MeCN) + OPR(3), is first-order in starting complex in acetonitrile. The reaction occurs via a dissociative interchange (I(d)) or associative interchange (I(a)) mechanism, depending on the nature of the phosphine oxide. The activation parameters for the solvolysis of Tp(iPr)MoO(OPh)(OPMe(3)) (DeltaH(++) = 56.3 kJ mol(-1); DeltaS(++) = -125.9 J mol(-1) K(-1); DeltaG(++) = 93.8 kJ mol(-1)) and Tp(iPr)MoO(OPh)(OPEtPh(2)) (DeltaH(++) = 66.5 kJ mol(-1); DeltaS(++) = -67.6 J mol(-1) K(-1); DeltaG(++) = 86.7 kJ mol(-1)) by acetonitrile are indicative of I(a) mechanisms. In contrast, the corresponding parameters for the solvolysis reaction of Tp(iPr)MoO(OPh)(OPEt(3)) (DeltaH(++) = 95.8 kJ mol(-1); DeltaS(++) = 26.0 J mol(-1) K(-1); DeltaG(++) = 88.1 kJ mol(-1)) and the remaining complexes by the same solvent are indicative of an I(d) mechanism. The equilibrium constant for the solvolysis of the oxo-Mo(V) phosphoryl complex, [Tp(iPr)MoO(OPh)(OPMe(3))](+), by acetonitrile was calculated to be 1.9 x 10(-6). The oxo-Mo(V) phosphoryl complex is more stable than the acetonitrile analogue, whereas the oxo-Mo(IV) acetonitrile complex is more stable than the phosphoryl analogue. The higher stability of the Mo(V) phosphoryl complex may explain the phosphate inhibition of sulfite oxidase.
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Affiliation(s)
- Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, USA.
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19
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Feng Y, Aponte J, Houseworth PJ, Boyle PD, Ison EA. Synthesis of Oxorhenium(V) Complexes with Diamido Amine Ancillary Ligands and Their Role in Oxygen Atom Transfer Catalysis. Inorg Chem 2009; 48:11058-66. [DOI: 10.1021/ic901434u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yuee Feng
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204
| | - Joel Aponte
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204
| | - Paul J. Houseworth
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204
| | - Paul D. Boyle
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204
| | - Elon A. Ison
- Department of Chemistry, North Carolina State University, 2620 Yarbrough Drive, Raleigh, North Carolina 27695-8204
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Richey C, Chovanec P, Hoeft SE, Oremland RS, Basu P, Stolz JF. Respiratory arsenate reductase as a bidirectional enzyme. Biochem Biophys Res Commun 2009; 382:298-302. [DOI: 10.1016/j.bbrc.2009.03.045] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2009] [Accepted: 03/04/2009] [Indexed: 11/30/2022]
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McNaughton RL, Lim BS, Knottenbelt SZ, Holm RH, Kirk ML. Spectroscopic and electronic structure studies of symmetrized models for reduced members of the dimethylsulfoxide reductase enzyme family. J Am Chem Soc 2008; 130:4628-36. [PMID: 18341333 DOI: 10.1021/ja074691b] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enzymes belonging to the dimethylsulfoxide reductase (DMSOR) family of pyranopterin Mo enzymes have a unique active-site geometry in the reduced form that lacks a terminal oxo ligand, unlike the reduced active sites of other pyranopterin Mo enzymes. Furthermore, the DMSOR family is characterized by the coordination of two pyranopterin-ene-1,2-dithiolate ligands in their active sites, which is distinctive among the other pyranopterin Mo enzymes but analogous to all of the currently known tungsten-containing enzymes. Electronic absorption, resonance Raman, and ground- and excited-state density functional calculations of symmetrized analogues of the reduced DMSOR active site ([NEt4][Mo(IV)(QAd)(S2C2Me2)2] where Ad = 2-adamantyl; Q = O, S, Se) have allowed for a detailed description of Mo-bisdithiolene electronic structure in the absence of a strong-field oxo ligand. The electronic absorption spectra are dominated by dithiolene S --> Mo charge-transfer transitions, and the totally symmetric Mo-S Raman stretch is observed at approximately 400 cm(-1) for all three complexes. These data indicate that the Mo-bisdithiolene bonding scheme in high-symmetry [Mo(QAd)(S2C2Me2)2]- complexes is not strongly perturbed by the apical QAd- ligands, but instead, the dithiolene ligands define the t(2g) ligand field splitting. The effects of conserved geometric distortions observed in DMSOR, relative to these high-symmetry models, were explored by spectroscopically calibrated bonding calculations, and the results are discussed within the context of electronic structure contributions to ground-state destabilization and transition-state stabilization. The specific electronic structure tuning of the endogenous amino acid ligation on the mechanism of DMSOR is also discussed.
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Affiliation(s)
- Rebecca L McNaughton
- Department of Chemistry, The University of New Mexico, MSC03 2060, Albuquerque, New Mexico 87131, USA
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22
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Boschi-Muller S, Gand A, Branlant G. The methionine sulfoxide reductases: Catalysis and substrate specificities. Arch Biochem Biophys 2008; 474:266-73. [PMID: 18302927 DOI: 10.1016/j.abb.2008.02.007] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 02/05/2008] [Accepted: 02/05/2008] [Indexed: 02/01/2023]
Abstract
Oxidation of Met residues in proteins leads to the formation of methionine sulfoxides (MetSO). Methionine sulfoxide reductases (Msr) are ubiquitous enzymes, which catalyze the reduction of the sulfoxide function of the oxidized methionine residues. In vivo, the role of Msrs is described as essential in protecting cells against oxidative damages and to play a role in infection of cells by pathogenic bacteria. There exist two structurally-unrelated classes of Msrs, called MsrA and MsrB, with opposite stereoselectivity towards the S and R isomers of the sulfoxide function, respectively. Both Msrs present a similar three-step catalytic mechanism. The first step, called the reductase step, leads to the formation of a sulfenic acid on the catalytic Cys with the concomitant release of Met. In recent years, significant efforts have been made to characterize structural and molecular factors involved in the catalysis, in particular of the reductase step, and in structural specificities.
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Affiliation(s)
- Sandrine Boschi-Muller
- UMR 7567 CNRS-UHP--Maturation des ARN et Enzymologie Moléculaire, Nancy Université, BP 239, 54506 Vandoeuvre-lès-Nancy, France.
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23
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Parkin G. Terminal Chalcogenido Complexes of the Transition Metals. PROGRESS IN INORGANIC CHEMISTRY 2007. [DOI: 10.1002/9780470166482.ch1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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24
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Daigle DJ, Decuir TJ, Robertson JB, Darensbourg DJ. 1,3,5-Triaz-7-Phosphatricyclo[3.3.1.1 3,7
]Decane and Derivatives. INORGANIC SYNTHESES 2007. [DOI: 10.1002/9780470132630.ch6] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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25
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Millar AJ, Doonan CJ, Smith PD, Nemykin VN, Basu P, Young CG. Oxygen atom transfer in models for molybdenum enzymes: isolation and structural, spectroscopic, and computational studies of intermediates in oxygen atom transfer from molybdenum(VI) to phosphorus(III). Chemistry 2006; 11:3255-67. [PMID: 15786505 DOI: 10.1002/chem.200401101] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Intermediates in the oxygen atom transfer from Mo(VI) to P(III), [Tp(iPr)MoOX(OPR3)] (Tp(iPr) = hydrotris(3-isopropylpyrazol-1-yl)borate; X = Cl-, phenolates, thiolates), have been isolated from the reactions of [Tp(iPr)MoO2X] with phosphines (PEt3, PMePh2, PPh3). The green, diamagnetic oxomolybdenum(IV) complexes possess local C(1) symmetry (by NMR spectroscopy) and exhibit IR bands assigned to nu(Mo==O) (approximately 950 cm(-1)) and nu(P==O) (1140-1083 cm(-1)) vibrations. The X-ray crystal structures of [Tp(iPr)MoOX(OPEt3)] (X = OC6H4-2-sBu, SnBu), [Tp(iPr)MoO(OPh)(OPMePh2)], and [Tp(iPr)MoOCl(OPPh3)] have been determined. The monomeric complexes exhibit distorted octahedral geometries, with coordination spheres composed of tridentate fac-Tp(iPr) and mutually cis monodentate terminal oxo, phosphoryl (phosphine oxide), and monoanionic X ligands. The electronic structures and stabilities of the complexes have been probed by computational methods, with the three-dimensional energy surfaces confirming the existence of a low-energy steric pocket that restricts the conformational freedom of the phosphoryl ligand and inhibits complete oxygen atom transfer. The reactivity of the complexes is also briefly described.
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Affiliation(s)
- Andrew J Millar
- School of Chemistry, University of Melbourne, Victoria, 3010, Australia
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26
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Cobb N, Conrads T, Hille R. Mechanistic Studies of Rhodobacter sphaeroides Me2SO Reductase. J Biol Chem 2005; 280:11007-17. [PMID: 15649898 DOI: 10.1074/jbc.m412050200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Studies of the molybdenum-containing dimethyl sulfoxide reductase from Rhodobacter sphaeroides have yielded new insight into its catalytic mechanism. A series of reductive titrations, performed over the pH range 6-10, reveal that the absorption spectrum of reduced enzyme is highly sensitive to pH. The reaction of reduced enzyme with dimethyl sulfoxide is found to be clearly biphasic throughout the pH range 6-8 with a fast, initial substrate-binding phase and substrate-concentration independent catalytic phase. The intermediate formed at the completion of the fast phase has the characteristic absorption spectrum of the established dimethyl sulfoxide-bound species. Quantitative reductive and oxidative titrations of the enzyme demonstrate that the molybdenum center takes up only two reducing equivalents, implying that the two pyranopterin equivalents of the molybdenum center are not formally redox active. Finally, the visible spectrum associated with the catalytically relevant "high-g split" Mo(V) species has been determined. Spectral deconvolution and EPR quantitation of enzyme-monitored turnover experiments with trimethylamine N-oxide as substrate reveal that no substrate-bound intermediate accumulates and that Mo(V) content remains near unity for the duration of the reaction. Similar experiments with dimethyl sulfoxide show that significant quantities of both the Mo(V) species and the dimethyl sulfoxide-bound complex accumulate during the course of reaction. Accumulation of the substrate-bound complex in the steady-state with dimethyl sulfoxide arises from partial reversal of the physiological reaction in which the accumulating product, dimethyl sulfide, reacts with oxidized enzyme to yield the substrate-bound intermediate, a process that significantly slows turnover.
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Affiliation(s)
- Nathan Cobb
- Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio 43210-1218, USA
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27
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Thapper A, Behrens A, Fryxelius J, Johansson MH, Prestopino F, Czaun M, Rehder D, Nordlander E. Synthesis and characterization of molybdenum oxo complexes of two tripodal ligands: reactivity studies of a functional model for molybdenum oxotransferases. Dalton Trans 2005:3566-71. [PMID: 16234939 DOI: 10.1039/b505180k] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented.
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Affiliation(s)
- Anders Thapper
- Inorganic Chemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, SE-221 00, Lund, Sweden
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28
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Phillips AD, Gonsalvi L, Romerosa A, Vizza F, Peruzzini M. Coordination chemistry of 1,3,5-triaza-7-phosphaadamantane (PTA). Coord Chem Rev 2004. [DOI: 10.1016/j.ccr.2004.03.010] [Citation(s) in RCA: 317] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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29
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Enemark JH, Cooney JJA, Wang JJ, Holm RH. Synthetic Analogues and Reaction Systems Relevant to the Molybdenum and Tungsten Oxotransferases. Chem Rev 2003; 104:1175-200. [PMID: 14871153 DOI: 10.1021/cr020609d] [Citation(s) in RCA: 424] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- John H Enemark
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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30
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Thapper A, Deeth RJ, Nordlander E. A density functional study of oxygen atom transfer reactions between biological oxygen atom donors and molybdenum(IV) bis(dithiolene) complexes. Inorg Chem 2002; 41:6695-702. [PMID: 12470064 DOI: 10.1021/ic020385h] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Density functional calculations have been used to investigate oxygen atom transfer reactions from the biological oxygen atom donors trimethylamine N-oxide (Me(3)NO) and dimethyl sulfoxide (DMSO) to the molybdenum(IV) complexes [MoO(mnt)(2)](2-) and [Mo(OCH(3))(mnt)(2)](-) (mnt = maleonitrile-1,2-dithiolate), which may serve as models for mononuclear molybdenum enzymes of the DMSO reductase family. The reaction between [MoO(mnt)(2)](2-) and trimethylamine N-oxide was found to have an activation energy of 72 kJ/mol and proceed via a transition state (TS) with distorted octahedral geometry, where the Me(3)NO is bound through the oxygen to the molybdenum atom and the N-O bond is considerably weakened. The computational modeling of the reactions between dimethyl sulfoxide (DMSO) and [MoO(mnt)(2)](2-) or [Mo(OCH(3))(mnt)(2)](-) indicated that the former is energetically unfavorable while the latter was found to be favorable. The addition of a methyl group to [MoO(mnt)(2)](2-) to form the corresponding des-oxo complex not only lowers the relative energy of the products but also lowers the activation energy. In addition, the reaction with [Mo(OCH(3))(mnt)(2)](-) proceeds via a TS with trigonal prismatic geometry instead of the distorted octahedral TS geometry modeled for the reaction between [MoO(mnt)(2)](2-) and Me(3)NO.
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Affiliation(s)
- Anders Thapper
- Inorganic Chemistry, Chemical Center, Lund University, Box 124, S-221 00 Lund, Sweden
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31
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Abstract
Molybdenum is the only second-row transition metal that is required by most living organisms, and the few species that do not require molybdenum use tungsten, which lies immediately below molybdenum in the periodic table. Because of their unique chemical versatility and unusually high bioavailability these two transition metals have been incorporated into the active sites of enzymes over the course of evolution. Enzymes that contain molybdenum or tungsten continue to be discovered and several crystal structures have become available recently. This new structural information has been complemented by spectroscopic and kinetic methods, as well as computational approaches. Together, these studies provide an increasingly detailed view of the reaction mechanisms and the correlation between the electronic structure of the active site and catalytic function, one of the fundamental goals in metallobiochemistry.
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Affiliation(s)
- Russ Hille
- Dept of Molecular and Cellular Biochemistry and The Protein Research Group, The Ohio State University, Columbus, OH 43210-1218, USA.
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32
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Schindelin H, Kisker C, Rajagopalan KV. Molybdopterin from molybdenum and tungsten enzymes. ADVANCES IN PROTEIN CHEMISTRY 2002; 58:47-94. [PMID: 11665493 DOI: 10.1016/s0065-3233(01)58002-x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- H Schindelin
- Department of Biochemistry, Center for Structural Biology, SUNY Stony Brook, Stony Brook, New York 11794, USA
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33
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Nemykin VN, Davie SR, Mondal S, Rubie N, Kirk ML, Somogyi A, Basu P. An analogue system displaying all the important processes of the catalytic cycles involving monooxomolybdenum(VI) and desoxomolybdenum(IV) centers. J Am Chem Soc 2002; 124:756-7. [PMID: 11817943 DOI: 10.1021/ja017178l] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mononuclear monooxomolybdenum(VI) complex hydrotris(3,5-dimethyl-1-pyrazolyl)borato(bis-4-ethoxyphenolato)oxomoylybdenum(VI) cation, [LMoVIO(p-OC6H4-OC2H5)2]+, where L- = hydrotris(3,5-dimethyl-1-pyrazolyl)borate, has been synthesized by chemical and electrochemical oxidation from the corresponding neutral oxomolybdenum(V) species, LMoVO(p-OC6H4-OC2H5)2. The molybdenum(VI) species has been characterized by NMR, IR, and resonance Raman spectroscopies, mass spectrometry, and electronic spectroscopy. Acetonitrile solutions of cationic [LMoVIO(p-OC6H4-OC2H5)2]+ react with tertiary phosphines (PR3) to generate phosphineoxide-bound adducts, [LMoIV(OPR3)(p-OC6H4-OC2H5)2]+, which subsequently generate the cationic desoxo species, [LMoIV(p-OC6H4-OC2H5)2]+ and OPR3. In the presence of water and an oxidizing agent the desoxo species generates the monooxomolybdenum(V), LMoVO(p-OC6H4-OC2H5)2, and completes the catalytic cycle. The oxygen atom transfer reaction has been probed by isotope-labeling experiments, vibrational spectroscopies, and mass spectrometry. This study describes an analogue complex that can exhibit all important processes of the catalytic cycle involving monooxomolybdenum(VI) and desoxomolybdenum(IV) centers.
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Affiliation(s)
- Victor N Nemykin
- The Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, USA
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34
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Affiliation(s)
- R Hille
- Department of Medical Biochemistry, Ohio State University, 333 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210-1218, USA
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35
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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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36
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Lim BS, Donahue JP, Holm RH. Synthesis and structures of bis(dithiolene)molybdenum complexes related to the active sites of the DMSO reductase enzyme family. Inorg Chem 2000; 39:263-73. [PMID: 11272534 DOI: 10.1021/ic9908672] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Structural analogues of the reduced (Mo(IV)) sites of members of the DMSO reductase family of molybdoenzymes are sought. These sites usually contain two pterin-dithiolene cofactor ligands and one protein-based ligand. Reaction of [Mo(MeCN)3(CO)3] and [Ni(S2C2R2)2] affords the trigonal prismatic complexes [Mo(CO)2(S2C2R2)2] (R = Me (1), Ph (2)), which by carbonyl substitution serve as useful precursors to a variety of bis(dithiolene)molybdenum-(IV,V) complexes. Reaction of 1 with Et4NOH yields [MoO(S2C2Me2)2]2- (3), which is readily oxidized to [MoO(S2C2Me2)2]1- (4). The hindered arene oxide ligands ArO- afford the square pyramidal complexes [Mo(OAr)(S2C2R2)2]1- (5, 6). The ligands PhQ- affordthe trigonal prismatic monocarbonyls [Mo(CO)(QPh)(S2C2Me2)2]1- (Q = S (8), Se (12)) while the bulky ligand ArS- forms square pyramidal [Mo(SAr)(S2C2R2)2]- (9, 10). In contrast, reactions with ArSe- result in [Mo(CO)(SeAr)(S2C2R2)2]1-(14, 15), which have not been successfully decarbonylated. Other compounds prepared by substitution reactions of 1 and 2 include the bridged dimers [Mo2(mu-Q)2(S2C2Me2)4]2- (Q = S (7), Se (11)) and [Mo2(mu-SePh)2(S2C2Ph2)4]2- (13). The complexes 1, 3-5, 7-10, 12-14, [Mo(S2C2Me2)3] (16), and [Mo(S2C2Me2)3]1- (17) were characterized by X-ray structure determinations. Certain complexes approach the binding arrangements in at least one DMSO reductase (5/6) and its Ser/Cys mutant, and in dissimilatory nitrate reductases (9/10). This investigation provides the initial demonstration of the new types of bis(dithiolene)molybdenum(IV) complexes available through [Mo(CO)2(S2C2R2)2] precursors, some of which will be utilized in reactivity studies. (Ar = 2,6-diisopropylphenyl or 2,4,6-triisopropylphenyl.)
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Affiliation(s)
- B S Lim
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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37
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Musgrave KB, Donahue JP, Lorber C, Holm RH, Hedman B, Hodgson KO. An X-ray Spectroscopic Investigation of Bis(dithiolene)molybdenum(IV,V,VI) and -tungsten(IV,V,VI) Complexes: Symmetrized Structural Representations of the Active Sites of Molybdoenzymes in the DMSO Reductase Family and of Tungstoenzymes in the AOR and F(M)DH Families. J Am Chem Soc 1999. [DOI: 10.1021/ja990753p] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kristin B. Musgrave
- Contribution from the Department of Chemistry, Stanford University, Stanford, California 94305, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - James P. Donahue
- Contribution from the Department of Chemistry, Stanford University, Stanford, California 94305, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Christian Lorber
- Contribution from the Department of Chemistry, Stanford University, Stanford, California 94305, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - R. H. Holm
- Contribution from the Department of Chemistry, Stanford University, Stanford, California 94305, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Britt Hedman
- Contribution from the Department of Chemistry, Stanford University, Stanford, California 94305, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Keith O. Hodgson
- Contribution from the Department of Chemistry, Stanford University, Stanford, California 94305, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
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38
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Reichenbecher W, Schink B. Towards the reaction mechanism of pyrogallol-phloroglucinol transhydroxylase of Pelobacter acidigallici. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1430:245-53. [PMID: 10082952 DOI: 10.1016/s0167-4838(99)00004-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Conversion of pyrogallol to phloroglucinol was studied with the molybdenum enzyme transhydroxylase of the strictly anaerobic fermenting bacterium Pelobacter acidigallici. Transhydroxylation experiments in H218O revealed that none of the hydroxyl groups of phloroglucinol was derived from water, confirming the concept that this enzyme transfers a hydroxyl group from the cosubstrate 1,2,3, 5-tetrahydroxybenzene (tetrahydroxybenzene) to the acceptor pyrogallol, and simultaneously regenerates the cosubstrate. This concept requires a reaction which synthesizes the cofactor de novo to maintain a sufficiently high intracellular pool during growth. Some sulfoxides and aromatic N-oxides were found to act as hydroxyl donors to convert pyrogallol to tetrahydroxybenzene. Again, water was not the source of the added hydroxyl groups; the oxides reacted as cosubstrates in a transhydroxylation reaction rather than as true oxidants in a net hydroxylation reaction. No oxidizing agent was found that supported a formation of tetrahydroxybenzene via a net hydroxylation of pyrogallol. However, conversion of pyrogallol to phloroglucinol in the absence of tetrahydroxybenzene was achieved if little pyrogallol and a high amount of enzyme preparation was used which had been pre-exposed to air. Obviously, the enzyme was oxidized by air to form sufficient amounts of tetrahydroxybenzene from pyrogallol to start the reaction. A reaction mechanism is proposed which combines an oxidative hydroxylation with a reductive dehydroxylation via the molybdenum cofactor, and allows the transfer of a hydroxyl group between tetrahydroxybenzene and pyrogallol without involvement of water. With this, the transhydroxylase differs basically from all other hydroxylating molybdenum enzymes which all use water as hydroxyl source.
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Affiliation(s)
- W Reichenbecher
- Fakultät für Biologie, Universität Konstanz, Postfach 5660, D-78457, Konstanz, Germany
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39
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Donahue JP, Goldsmith CR, Nadiminti U, Holm RH. Synthesis, Structures, and Reactivity of Bis(dithiolene)molybdenum(IV,VI) Complexes Related to the Active Sites of Molybdoenzymes. J Am Chem Soc 1998. [DOI: 10.1021/ja982914f] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James P. Donahue
- Contribution from the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Christian R. Goldsmith
- Contribution from the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Uma Nadiminti
- Contribution from the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - R. H. Holm
- Contribution from the Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
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40
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Hille R, Rétey J, Bartlewski-Hof U, Reichenbecher W. Mechanistic aspects of molybdenum-containing enzymes. FEMS Microbiol Rev 1998; 22:489-501. [PMID: 10189201 DOI: 10.1111/j.1574-6976.1998.tb00383.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Affiliation(s)
- R Hille
- Department of Medical Biochemistry, Ohio State University, Columbus 43210-1218, USA
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Abu-Omar MM, Khan SI. Molecular Rhenium(V) Oxotransferases: Oxidation of Thiols to Disulfides with Sulfoxides. The Case of Substrate-Inhibited Catalysis. Inorg Chem 1998; 37:4979-4985. [PMID: 11670665 DOI: 10.1021/ic980348j] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Re(O)Cl(3)(PPh(3))(2), 1, and Re(O)Cl(3)(OPPh(3))(Me(2)S), 2, catalyze the oxidation of thiols to disulfides with sulfoxides under mild conditions. Catalyst 1 exhibits an induction period which features PPh(3) oxidation to OPPh(3) prior to disulfide formation. This lag is absent when 2 is the catalyst precursor. Otherwise, 1 and 2 display comparable kinetics and concentration dependencies. The catalytic reactions are first-order in catalyst, inhibited by thiol, and first-order in sulfoxide at low sulfoxide concentrations. Thiol inhibits the oxygen-transfer reaction because it competes with sulfoxide for coordination on rhenium. Sulfoxides must bind to rhenium in order to be activated for oxo transfer. Ligand substitution reactions of 1 and 2 display kinetics that are consistent with a dissociative (D) mechanism: the substitution rate is zero-order in entering ligand and inhibited by departing ligand. The first-order rate constant for the formation of a 5-coordinate intermediate is 0.06 s(-)(1). As the sulfoxide concentration is increased, the reaction rate increases to reach a maximum and then begins to decline. The catalytic turnover rate at optimal conditions (maximum k(cat) for PhS(O)Me is 180 h(-)(1)) approaches the rate of ligand substitution in these rhenium(V) complexes. Rate retardation at high sulfoxide concentrations is due to catalyst deactivation; sulfoxides oxidize the rhenium(V) catalyst to ReO(4)(-), which is inactive. Dimethyl sulfoxide (DMSO) is more efficient than aryl sulfoxides at oxidizing the catalyst, a fact that could be rationalized by the thermodynamics of S-O bond strength. Thus, aryl sulfoxides, such as PhS(O)Me, appear to be more reactive than alkyl ones. The oxygen-transfer reaction, therefore, is not involved in the rate-controlling step and the rate is limited by ligand substitution. The rhenium(V) catalyst in these reactions acts as a Lewis acid and activates the sulfoxide via coordination: the sulfoxide ligand and not the metal is the bearer of the transferred oxygen. A single-crystal X-ray structure of Re(O)Cl(3)(OPPh(3))(Me(2)S), 2, has been solved: space group Pcmn, a = 8.863(6) Å, b = 14.269(9) Å, c = 18.45(1) Å, Z = 4; the structure was refined to final residuals R = 0.028 and R(w) = 0.035.
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Affiliation(s)
- Mahdi M. Abu-Omar
- Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California 90095-1569
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Romão MJ, Knäblein J, Huber R, Moura JJ. Structure and function of molybdopterin containing enzymes. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1998; 68:121-44. [PMID: 9652170 DOI: 10.1016/s0079-6107(97)00022-9] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Molybdopterin containing enzymes are present in a wide range of living systems and have been known for several decades. However, only in the past two years have the first crystal structures been reported for this type of enzyme. This has represented a major breakthrough in this field. The enzymes share common structural features, but reveal different polypeptide folding topologies. In this review we give an account of the related spectroscopic information and the crystallographic results, with emphasis on structure-function studies.
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Affiliation(s)
- M J Romão
- Instituto de Tecnologia Química e Biológica, Oeiras, Portugal.
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43
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Abstract
Protein X-ray crystallography has revealed the structures of the active sites of several molybdenum- and tungsten-containing enzymes that catalyze formal hydroxylation and oxygen atom transfer reactions. Each molybdenum (or tungsten) atom is coordinated by one (or two) ene-dithiolate groups of a novel pterin (molybdopterin), and the active sites are further differentiated from one another by the number of terminal oxo and/or sulfido groups and by coordinated amino acid residues. These active-site structures have no precedent in the coordination chemistry of molybdenum and tungsten.
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Affiliation(s)
- J McMaster
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA.
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Donahue JP, Lorber C, Nordlander E, Holm RH. Molybdenum and Tungsten Structural Analogues of the Active Sites of the MoIV + [O] → MoVIO Oxygen Atom Transfer Couple of DMSO Reductases. J Am Chem Soc 1998. [DOI: 10.1021/ja973917f] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- James P. Donahue
- Department of Chemistry and Chemical Biology Harvard University, Cambridge, Massachusetts 02138 Inorganic Chemistry 1, Chemical Center Lund University, S-22100 Lund, Sweden
| | - Christian Lorber
- Department of Chemistry and Chemical Biology Harvard University, Cambridge, Massachusetts 02138 Inorganic Chemistry 1, Chemical Center Lund University, S-22100 Lund, Sweden
| | - Ebbe Nordlander
- Department of Chemistry and Chemical Biology Harvard University, Cambridge, Massachusetts 02138 Inorganic Chemistry 1, Chemical Center Lund University, S-22100 Lund, Sweden
| | - R. H. Holm
- Department of Chemistry and Chemical Biology Harvard University, Cambridge, Massachusetts 02138 Inorganic Chemistry 1, Chemical Center Lund University, S-22100 Lund, Sweden
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45
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Tucci GC, Donahue JP, Holm RH. Comparative Kinetics of Oxo Transfer to Substrate Mediated by Bis(dithiolene)dioxomolybdenum and -tungsten Complexes. Inorg Chem 1998. [DOI: 10.1021/ic971426q] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gregory C. Tucci
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - James P. Donahue
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
| | - R. H. Holm
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138
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46
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McAlpine AS, McEwan AG, Bailey S. The high resolution crystal structure of DMSO reductase in complex with DMSO. J Mol Biol 1998; 275:613-23. [PMID: 9466935 DOI: 10.1006/jmbi.1997.1513] [Citation(s) in RCA: 143] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The crystal structure of the molybdenum enzyme dimethylsulphoxide reductase (DMSOR) has been determined at 1.9 A resolution with substrate bound at the active site. DMSOR is an oxotransferase which catalyses the reduction of dimethylsulphoxide (DMSO) to dimethylsulphide (DMS) in a two stage reaction which is linked to oxygen atom transfer and electron transfer. In the first step, DMSO binds to reduced (Mo(IV)) enzyme, the enzyme is oxidised to Mo(VI) with an extra oxygen ligand and DMS is released. Regeneration of reduced enzyme is achieved by transfer of two electrons, successively from a specific cytochrome, and release of the oxygen as water. The enzyme, purified under aerobic conditions, is in the oxidised (Mo(VI)) state. Addition of a large excess of DMS to the oxidised enzyme in solution causes a change in the absorption spectrum of the enzyme. The same reaction occurs within crystals of the enzyme and the crystal structure reveals a complex with DMSO bound to the molybdenum via its oxygen atom. X-ray edge data indicate that the metal is in the Mo(IV) state. The DMSO ligand replaces one of the two oxo groups which ligate the oxidised form of the enzyme, suggesting very strongly that this is the oxygen which is transferred during catalysis. Residues 384 to 390, disordered in the oxidised enzyme, are now clearly seen in the cleft leading to the active site. The side-chain of Trp388 forms a lid trapping the substrate/product.
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47
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Eagle AA, Tiekink ERT, Young CG. Dioxotungsten(VI) Complexes of Hydrotris(3,5-dimethylpyrazol-1-yl)borate Including the X-ray Crystal Structure of the Tungsten Selenophenolate Complex cis-{HB(Me2C3N2H)3}WO2(SePh). Inorg Chem 1997. [DOI: 10.1021/ic970544a] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Aston A. Eagle
- School of Chemistry, University of Melbourne, Parkville, Victoria 3052, Australia, and Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Edward R. T. Tiekink
- School of Chemistry, University of Melbourne, Parkville, Victoria 3052, Australia, and Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
| | - Charles G. Young
- School of Chemistry, University of Melbourne, Parkville, Victoria 3052, Australia, and Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
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48
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Dutta SK, McConville DB, Youngs WJ, Chaudhury M. Reactivity of Mo−Ot Terminal Bonds toward Substrates Having Simultaneous Proton- and Electron-Donor Properties: A Rudimentary Functional Model for Oxotransferase Molybdenum Enzymes. Inorg Chem 1997. [DOI: 10.1021/ic960670z] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Subodh Kanti Dutta
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India, and Department of Chemistry, University of Akron, Akron, Ohio 44325-3601
| | - David B. McConville
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India, and Department of Chemistry, University of Akron, Akron, Ohio 44325-3601
| | - Wiley J. Youngs
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India, and Department of Chemistry, University of Akron, Akron, Ohio 44325-3601
| | - Muktimoy Chaudhury
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India, and Department of Chemistry, University of Akron, Akron, Ohio 44325-3601
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49
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Knäblein J, Dobbek H, Ehlert S, Schneider F. Isolation, cloning, sequence analysis and X-ray structure of dimethyl sulfoxide/trimethylamine N-oxide reductase from Rhodobacter capsulatus. Biol Chem 1997; 378:293-302. [PMID: 9165084 DOI: 10.1515/bchm.1997.378.3-4.293] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The periplasmic enzyme dimethyl sulfoxide/trimethylamine N-oxide reductase (DMSOR/TMAOR) from the photosynthetic purple bacterium Rhodobacter capsulatus functions as the terminal electron acceptor in its respiratory chain. The enzyme catalyzes the reduction of highly oxidized substrates like dimethyl sulfoxide (DMSO) or trimethylamine N-oxide (TMAO). At a molybdenum redox centre, two single electrons are transferred from cytochrome c556 to the substrate, e.g. DMSO, generating dimethyl sulfide (DMS) and water. The operon encoding this enzyme was isolated, cloned and sequenced, and its chromosomal location determined. It was shown by analytical and crystallographic data that DMSOR and TMAOR are identical enzymes. Degenerate primers were derived from short peptide sequences and a 700 bp fragment was amplified by nested PCR, subsequently cloned and radioactively labeled to screen a prepared lambda DASH library. Positive lambda clones were subcloned into pBluescript and subsequently transformed into Escherichia coli to sequence the DMSOR/TMAOR operon. By an optimized protein purification high yields (5 mg protein/l culture) with a specific activity of 30 U/mg were obtained. The molecular mass was experimentally determined by electrospray mass spectroscopy (MS) to be 85034 Da and from the deduced amino acid sequence of the apoenzyme to be 85033 Da. The enzyme was crystallized in space group P4(1)2(1)2 with unit cell dimensions of a = b = 80.7 A and c = 229.2 A diffracting beyond 1.8 A. The three-dimensional structure was solved by a combination of multiple isomorphous replacement (MIR) and molecular replacement techniques. The atomic model was refined to an R-factor of 0.169 for 57394 independent reflections. The spherical protein consists of four domains with a funnel-like cavity that leads to the freely accessible metal-ion redox center. The sole bis(molybdopterin guanine dinucleotide)molybdenum cofactor (1541 Da) of the single chain protein has the molybdenum ion bound to the cis-dithiolene group of only one molybdopterin guanine dinucleotide (MGD) molecule. In addition, two oxo ligands and the oxygen of a serine side chain are bound to the molybdenum ion.
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Affiliation(s)
- J Knäblein
- Max-Planck-Institut für Biochemie, Martinsried, Germany
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50
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Abstract
Molybdenum-containing enzymes catalyze basic metabolic reactions in the nitrogen, sulfur, and carbon cycles. With the exception of the nitrogenase cofactor, molybdenum is incorporated into proteins as the molybdenum cofactor that contains a mononuclear molybdenum atom coordinated to the sulfur atoms of a pterin derivative named molybdopterin. Certain microorganisms can also utilize tungsten in a similar fashion. Molybdenum-cofactor-containing enzymes catalyze the transfer of an oxygen atom, ultimately derived from or incorporated into water, to or from a substrate in a two-electron redox reaction. On the basis of sequence alignments and spectroscopic properties, four families of molybdenum-cofactor-containing enzymes have been identified. The available crystallographic structures for members of these families are discussed within the framework of the active site structure and catalytic mechanisms of molybdenum-cofactor-containing enzymes. Although the function of the molybdopterin ligand has not yet been conclusively established, interactions of this ligand with the coordinated metal are sensitive to the oxidation state, indicating that the molybdopterin may be directly involved in the enzymatic mechanism.
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Affiliation(s)
- C Kisker
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125, USA
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