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Qu Y, Shi S, Zhou H, Ma Q, Li X, Zhang X, Zhou J. Characterization of a novel phenol hydroxylase in indoles biotransformation from a strain Arthrobacter sp. W1 [corrected]. PLoS One 2012; 7:e44313. [PMID: 23028517 PMCID: PMC3441600 DOI: 10.1371/journal.pone.0044313] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 08/01/2012] [Indexed: 11/30/2022] Open
Abstract
Background Indigoids, as popular dyes, can be produced by microbial strains or enzymes catalysis. However, the new valuable products with their transformation mechanisms, especially inter-conversion among the intermediates and products have not been clearly identified yet. Therefore, it is necessary to investigate novel microbial catalytic processes for indigoids production systematically. Findings A phenol hydroxylase gene cluster (4,606 bp) from Arthrobacter sp. W1 (PHw1) was obtained. This cluster contains six components in the order of KLMNOP, which exhibit relatively low sequence identities (37–72%) with known genes. It was suggested that indole and all the tested indole derivatives except for 3-methylindole were transformed to various substituted indigoid pigments, and the predominant color products derived from indoles were identified by spectrum analysis. One new purple product from indole, 2-(7-oxo-1H-indol-6(7H)-ylidene) indolin-3-one, should be proposed as the dimerization of isatin and 7-hydroxylindole at the C-2 and C-6 positions. Tunnel entrance and docking studies were used to predict the important amino acids for indoles biotransformation, which were further proved by site-directed mutagenesis. Conclusions/Significance We showed that the phenol hydroxylase from genus Arthrobacter could transform indoles to indigoids with new chemical compounds being produced. Our work should show high insights into understanding the mechanism of indigoids bio-production.
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Affiliation(s)
- Yuanyuan Qu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian, China.
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52
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Biotransformation of benzene and toluene to catechols by phenol hydroxylase from Arthrobacter sp. W1. Appl Microbiol Biotechnol 2012; 97:5097-103. [DOI: 10.1007/s00253-012-4301-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 07/12/2012] [Accepted: 07/12/2012] [Indexed: 10/28/2022]
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53
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Kodera M, Kawahara Y, Hitomi Y, Nomura T, Ogura T, Kobayashi Y. Reversible O-O bond scission of peroxodiiron(III) to high-spin oxodiiron(IV) in dioxygen activation of a diiron center with a bis-tpa dinucleating ligand as a soluble methane monooxygenase model. J Am Chem Soc 2012; 134:13236-9. [PMID: 22839735 DOI: 10.1021/ja306089q] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conversion of peroxodiiron(III) to high-spin S = 2 oxodiiron(IV) via reversible O-O bond scission in a diiron complex with a bis-tpa dinucleating ligand, 6-hpa, has been characterized by elemental analysis; kinetic measurements for alkene epoxidation; cold-spray ionization mass spectrometry; and electronic absorption, Mössbauer, and resonance Raman spectroscopy to gain insight into the O(2) activation mechanism of soluble methane monooxygenases. This is the first synthetic example of a high-spin S = 2 oxodiiron(IV) species that oxidizes alkenes to epoxides efficiently. The bistability of the peroxodiiron(III) and high-spin S = 2 oxodiiron(IV) moieties is the key feature for the reversible O-O bond scission.
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Affiliation(s)
- Masahito Kodera
- Department of Molecular Chemistry and Biochemistry, Doshisha University, Tatara Miyakotani 1-3, Kyotanabe, Kyoto 610-0321, Japan.
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Li F, Chakrabarti M, Dong Y, Kauffmann K, Bominaar EL, Münck E, Que L. Structural, EPR, and Mössbauer characterization of (μ-alkoxo)(μ-carboxylato)diiron(II,III) model complexes for the active sites of mixed-valent diiron enzymes. Inorg Chem 2012; 51:2917-29. [PMID: 22360600 PMCID: PMC3298377 DOI: 10.1021/ic2021726] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To obtain structural and spectroscopic models for the diiron(II,III) centers in the active sites of diiron enzymes, the (μ-alkoxo)(μ-carboxylato)diiron(II,III) complexes [Fe(II)Fe(III)(N-Et-HPTB)(O(2)CPh)(NCCH(3))(2)](ClO(4))(3) (1) and [Fe(II)Fe(III)(N-Et-HPTB)(O(2)CPh)(Cl)(HOCH(3))](ClO(4))(2) (2) (N-Et-HPTB = N,N,N',N'-tetrakis(2-(1-ethyl-benzimidazolylmethyl))-2-hydroxy-1,3-diaminopropane) have been prepared and characterized by X-ray crystallography, UV-visible absorption, EPR, and Mössbauer spectroscopies. Fe1-Fe2 separations are 3.60 and 3.63 Å, and Fe1-O1-Fe2 bond angles are 128.0° and 129.4° for 1 and 2, respectively. Mössbauer and EPR studies of 1 show that the Fe(III) (S(A) = 5/2) and Fe(II) (S(B) = 2) sites are antiferromagnetically coupled to yield a ground state with S = 1/2 (g= 1.75, 1.88, 1.96); Mössbauer analysis of solid 1 yields J = 22.5 ± 2 cm(-1) for the exchange coupling constant (H = JS(A)·S(B) convention). In addition to the S = 1/2 ground-state spectrum of 1, the EPR signal for the S = 3/2 excited state of the spin ladder can also be observed, the first time such a signal has been detected for an antiferromagnetically coupled diiron(II,III) complex. The anisotropy of the (57)Fe magnetic hyperfine interactions at the Fe(III) site is larger than normally observed in mononuclear complexes and arises from admixing S > 1/2 excited states into the S = 1/2 ground state by zero-field splittings at the two Fe sites. Analysis of the "D/J" mixing has allowed us to extract the zero-field splitting parameters, local g values, and magnetic hyperfine structural parameters for the individual Fe sites. The methodology developed and followed in this analysis is presented in detail. The spin Hamiltonian parameters of 1 are related to the molecular structure with the help of DFT calculations. Contrary to what was assumed in previous studies, our analysis demonstrates that the deviations of the g values from the free electron value (g = 2) for the antiferromagnetically coupled diiron(II,III) core in complex 1 are predominantly determined by the anisotropy of the effective g values of the ferrous ion and only to a lesser extent by the admixture of excited states into ground-state ZFS terms (D/J mixing). The results for 1 are discussed in the context of the data available for diiron(II,III) clusters in proteins and synthetic diiron(II,III) complexes.
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Affiliation(s)
- Feifei Li
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
| | | | - Yanhong Dong
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
| | - Karl Kauffmann
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Emile L. Bominaar
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455
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55
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Srnec M, Rokob TA, Schwartz JK, Kwak Y, Rulíšek L, Solomon EI. Structural and Spectroscopic Properties of the Peroxodiferric Intermediate of Ricinus communis Soluble Δ9 Desaturase. Inorg Chem 2012; 51:2806-20. [DOI: 10.1021/ic2018067] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Martin Srnec
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences & IOCB Research Center, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 166 10 Praha 6, Czech Republic
| | - Tibor András Rokob
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences & IOCB Research Center, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 166 10 Praha 6, Czech Republic
| | - Jennifer K. Schwartz
- Department of Chemistry, Stanford University, Stanford, California 94305-5080,
United States
| | - Yeonju Kwak
- Department of Chemistry, Stanford University, Stanford, California 94305-5080,
United States
| | - Lubomír Rulíšek
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences & IOCB Research Center, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 166 10 Praha 6, Czech Republic
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305-5080,
United States
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Mikhalyova EA, Makhlynets OV, Palluccio TD, Filatov AS, Rybak-Akimova EV. A new efficient ironcatalyst for olefinepoxidation with hydrogen peroxide. Chem Commun (Camb) 2012; 48:687-9. [DOI: 10.1039/c1cc15935f] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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57
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McCormick MS, Lippard SJ. Analysis of substrate access to active sites in bacterial multicomponent monooxygenase hydroxylases: X-ray crystal structure of xenon-pressurized phenol hydroxylase from Pseudomonas sp. OX1. Biochemistry 2011; 50:11058-69. [PMID: 22136180 PMCID: PMC3243792 DOI: 10.1021/bi201248b] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In all structurally characterized bacterial multicomponent monooxygenase (BMM) hydroxylase proteins, a series of hydrophobic cavities in the α-subunit trace a conserved path from the protein exterior to the carboxylate-bridged diiron active site. This study examines these cavities as a potential route for transport of dioxygen to the active site by crystallographic characterization of a xenon-pressurized sample of the hydroxylase component of phenol hydroxylase from Pseudomonas sp. OX1. Computational analyses of the hydrophobic cavities in the hydroxylase α-subunits of phenol hydroxylase (PHH), soluble methane monooxygenase (MMOH), and toluene/o-xylene monooxygenase (ToMOH) are also presented. The results, together with previous findings from crystallographic studies of xenon-pressurized sMMO hydroxylase, clearly identify the propensity for these cavities to bind hydrophobic gas molecules in the protein interior. This proposed functional role is supported by recent stopped flow kinetic studies of ToMOH variants [Song, W. J., et al. (2011) Proc. Natl. Acad. Sci. U.S.A.108, 14795-14800]. In addition to information about the Xe sites, the structure determination revealed significantly weakened binding of regulatory protein to the hydroxylase in comparison to that in the previously reported structure of PHH, as well as the presence of a newly identified metal-binding site in the α-subunit that adopts a linear coordination environment consistent with Cu(I), and a glycerol molecule bound to Fe1 in a fashion that is unique among hydrocarbon-diiron site adducts reported to date in BMM hydroxylase structures. Finally, a comparative analysis of the α-subunit structures of PHH, MMOH, and ToMOH details proposed routes for the other three BMM substrates, the hydrocarbon, electrons, and protons, comprising cavities, channels, hydrogen-bonding networks, and pores in the structures of their α-subunits.
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Affiliation(s)
- Michael S. McCormick
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA 02139
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA 02139
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58
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Xue G, Pokutsa A, Que L. Substrate-triggered activation of a synthetic [Fe2(μ-O)2] diamond core for C-H bond cleavage. J Am Chem Soc 2011; 133:16657-67. [PMID: 21899336 DOI: 10.1021/ja207131g] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
An [Fe(IV)(2)(μ-O)(2)] diamond core structure has been postulated for intermediate Q of soluble methane monooxygenase (sMMO-Q), the oxidant responsible for cleaving the strong C-H bond of methane and its hydroxylation. By extension, analogous species may be involved in the mechanisms of related diiron hydroxylases and desaturases. Because of the paucity of well-defined synthetic examples, there are few, if any, mechanistic studies on the oxidation of hydrocarbon substrates by complexes with high-valent [Fe(2)(μ-O)(2)] cores. We report here that water or alcohol substrates can activate synthetic [Fe(III)Fe(IV)(μ-O)(2)] complexes supported by tetradentate tris(pyridyl-2-methyl)amine ligands (1 and 2) by several orders of magnitude for C-H bond oxidation. On the basis of detailed kinetic studies, it is postulated that the activation results from Lewis base attack on the [Fe(III)Fe(IV)(μ-O)(2)] core, resulting in the formation of a more reactive species with a [X-Fe(III)-O-Fe(IV)═O] ring-opened structure (1-X, 2-X, X = OH(-) or OR(-)). Treatment of 2 with methoxide at -80 °C forms the 2-methoxide adduct in high yield, which is characterized by an S = 1/2 EPR signal indicative of an antiferromagnetically coupled [S = 5/2 Fe(III)/S = 2 Fe(IV)] pair. Even at this low temperature, the complex undergoes facile intramolecular C-H bond cleavage to generate formaldehyde, showing that the terminal high-spin Fe(IV)═O unit is capable of oxidizing a C-H bond as strong as 96 kcal mol(-1). This intramolecular oxidation of the methoxide ligand can in fact be competitive with intermolecular oxidation of triphenylmethane, which has a much weaker C-H bond (D(C-H) 81 kcal mol(-1)). The activation of the [Fe(III)Fe(IV)(μ-O)(2)] core is dramatically illustrated by the oxidation of 9,10-dihydroanthracene by 2-methoxide, which has a second-order rate constant that is 3.6 × 10(7)-fold larger than that for the parent diamond core complex 2. These observations provide strong support for the DFT-based notion that an S = 2 Fe(IV)═O unit is much more reactive at H-atom abstraction than its S = 1 counterpart and suggest that core isomerization could be a viable strategy for the [Fe(IV)(2)(μ-O)(2)] diamond core of sMMO-Q to selectively attack the strong C-H bond of methane in the presence of weaker C-H bonds of amino acid residues that define the diiron active site pocket.
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Affiliation(s)
- Genqiang Xue
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA
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59
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O’Reilly ME, Del Castillo TJ, Falkowski JM, Ramachandran V, Pati M, Correia MC, Abboud KA, Dalal NS, Richardson DE, Veige AS. Autocatalytic O2 Cleavage by an OCO3– Trianionic Pincer CrIII Complex: Isolation and Characterization of the Autocatalytic Intermediate [CrIV]2(μ-O) Dimer. J Am Chem Soc 2011; 133:13661-73. [DOI: 10.1021/ja2050474] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matthew E. O’Reilly
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Trevor J. Del Castillo
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Joseph M. Falkowski
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Vasanth Ramachandran
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Mekhala Pati
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Marie C. Correia
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Khalil A. Abboud
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Naresh S. Dalal
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - David E. Richardson
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
| | - Adam S. Veige
- Department of Chemistry, Center for Catalysis, University of Florida, P.O. Box 117200, Gainesville, Florida 32611, United States
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Notomista E, Scognamiglio R, Troncone L, Donadio G, Pezzella A, Di Donato A, Izzo V. Tuning the specificity of the recombinant multicomponent toluene o-xylene monooxygenase from Pseudomonas sp. strain OX1 for the biosynthesis of tyrosol from 2-phenylethanol. Appl Environ Microbiol 2011; 77:5428-37. [PMID: 21666013 PMCID: PMC3147462 DOI: 10.1128/aem.00461-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 06/01/2011] [Indexed: 12/27/2022] Open
Abstract
Biocatalysis is today a standard technology for the industrial production of several chemicals, and the number of biotransformation processes running on a commercial scale is constantly increasing. Among biocatalysts, bacterial multicomponent monooxygenases (BMMs), a diverse group of nonheme diiron enzymes that activate dioxygen, are of primary interest due to their ability to catalyze a variety of complex oxidations, including reactions of mono- and dihydroxylation of phenolic compounds. In recent years, both directed evolution and rational design have been successfully used to identify the molecular determinants responsible for BMM regioselectivity and to improve their activity toward natural and nonnatural substrates. Toluene o-xylene monooxygenase (ToMO) is a BMM isolated from Pseudomonas sp. strain OX1 which hydroxylates a wide spectrum of aromatic compounds. In this work we investigate the use of recombinant ToMO for the biosynthesis in recombinant cells of Escherichia coli strain JM109 of 4-hydroxyphenylethanol (tyrosol), an antioxidant present in olive oil, from 2-phenylethanol, a cheap and commercially available substrate. We initially found that wild-type ToMO is unable to convert 2-phenylethanol to tyrosol. This was explained by using a computational model which analyzed the interactions between ToMO active-site residues and the substrate. We found that residue F176 is the major steric hindrance for the correct positioning of the reaction intermediate leading to tyrosol production into the active site of the enzyme. Several mutants were designed and prepared, and we found that the combination of different mutations at position F176 with mutation E103G allows ToMO to convert up to 50% of 2-phenylethanol into tyrosol in 2 h.
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Affiliation(s)
- Eugenio Notomista
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Via Cinthia, I-80126 Naples, and CEINGE-Biotecnologie Avanzate s.c.ar.l., Naples, Italy
| | - Roberta Scognamiglio
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Via Cinthia, I-80126 Naples, and CEINGE-Biotecnologie Avanzate s.c.ar.l., Naples, Italy
| | - Luca Troncone
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Via Cinthia, I-80126 Naples, and CEINGE-Biotecnologie Avanzate s.c.ar.l., Naples, Italy
| | - Giuliana Donadio
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Via Cinthia, I-80126 Naples, and CEINGE-Biotecnologie Avanzate s.c.ar.l., Naples, Italy
| | - Alessandro Pezzella
- Dipartimento di Chimica Organica e Biochimica, Università di Napoli Federico II, Via Cinthia, 80126 Naples, Italy
| | - Alberto Di Donato
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Via Cinthia, I-80126 Naples, and CEINGE-Biotecnologie Avanzate s.c.ar.l., Naples, Italy
| | - Viviana Izzo
- Dipartimento di Biologia Strutturale e Funzionale, Università di Napoli Federico II, Via Cinthia, I-80126 Naples, and CEINGE-Biotecnologie Avanzate s.c.ar.l., Naples, Italy
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Liang L, Chang Y, Shih H, Lin S, Lee HM. Synthesis and Structural Characterization of Lithium and Iron Complexes Containing a Chelating Phenolate Phosphane Ligand. Eur J Inorg Chem 2011. [DOI: 10.1002/ejic.201100260] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Lan‐Chang Liang
- Department of Chemistry and Center for Nanoscience & Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Yu‐Ning Chang
- Department of Chemistry and Center for Nanoscience & Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Huan‐Yu Shih
- Department of Chemistry and Center for Nanoscience & Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Sheng‐Ta Lin
- Department of Chemistry and Center for Nanoscience & Nanotechnology, National Sun Yat‐sen University, Kaohsiung 80424, Taiwan
| | - Hon Man Lee
- Department of Chemistry, National Changhua University of Education, Changhua 50058, Taiwan
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Rather LJ, Weinert T, Demmer U, Bill E, Ismail W, Fuchs G, Ermler U. Structure and mechanism of the diiron benzoyl-coenzyme A epoxidase BoxB. J Biol Chem 2011; 286:29241-29248. [PMID: 21632537 DOI: 10.1074/jbc.m111.236893] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The coenzyme A (CoA)-dependent aerobic benzoate metabolic pathway uses an unprecedented chemical strategy to overcome the high aromatic resonance energy by forming the non-aromatic 2,3-epoxybenzoyl-CoA. The crucial dearomatizing reaction is catalyzed by three enzymes, BoxABC, where BoxA is an NADPH-dependent reductase, BoxB is a benzoyl-CoA 2,3-epoxidase, and BoxC is an epoxide ring hydrolase. We characterized the key enzyme BoxB from Azoarcus evansii by structural and Mössbauer spectroscopic methods as a new member of class I diiron enzymes. Several family members were structurally studied with respect to the diiron center architecture, but no structure of an intact diiron enzyme with its natural substrate has been reported. X-ray structures between 1.9 and 2.5 Å resolution were determined for BoxB in the diferric state and with bound substrate benzoyl-CoA in the reduced state. The substrate-bound reduced state is distinguished from the diferric state by increased iron-ligand distances and the absence of directly bridging groups between them. The position of benzoyl-CoA inside a 20 Å long channel and the position of the phenyl ring relative to the diiron center are accurately defined. The C2 and C3 atoms of the phenyl ring are closer to one of the irons. Therefore, one oxygen of activated O(2) must be ligated predominantly to this proximate iron to be in a geometrically suitable position to attack the phenyl ring. Consistent with the observed iron/phenyl geometry, BoxB stereoselectively should form the 2S,3R-epoxide. We postulate a reaction cycle that allows a charge delocalization because of the phenyl ring and the electron-withdrawing CoA thioester.
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Affiliation(s)
- Liv J Rather
- Mikrobiologie, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg
| | - Tobias Weinert
- Max-Planck-Institut für Biophysik, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, and
| | - Ulrike Demmer
- Max-Planck-Institut für Biophysik, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, and
| | - Eckhard Bill
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Wael Ismail
- Mikrobiologie, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg
| | - Georg Fuchs
- Mikrobiologie, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg
| | - Ulrich Ermler
- Max-Planck-Institut für Biophysik, Max-von-Laue-Strasse 3, D-60438 Frankfurt am Main, and.
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Bochevarov AD, Li J, Song WJ, Friesner RA, Lippard SJ. Insights into the different dioxygen activation pathways of methane and toluene monooxygenase hydroxylases. J Am Chem Soc 2011; 133:7384-97. [PMID: 21517016 PMCID: PMC3092846 DOI: 10.1021/ja110287y] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The methane and toluene monooxygenase hydroxylases (MMOH and TMOH, respectively) have almost identical active sites, yet the physical and chemical properties of their oxygenated intermediates, designated P*, H(peroxo), Q, and Q* in MMOH and ToMOH(peroxo) in a subclass of TMOH, ToMOH, are substantially different. We review and compare the structural differences in the vicinity of the active sites of these enzymes and discuss which changes could give rise to the different behavior of H(peroxo) and Q. In particular, analysis of multiple crystal structures reveals that T213 in MMOH and the analogous T201 in TMOH, located in the immediate vicinity of the active site, have different rotatory configurations. We study the rotational energy profiles of these threonine residues with the use of molecular mechanics (MM) and quantum mechanics/molecular mechanics (QM/MM) computational methods and put forward a hypothesis according to which T213 and T201 play an important role in the formation of different types of peroxodiiron(III) species in MMOH and ToMOH. The hypothesis is indirectly supported by the QM/MM calculations of the peroxodiiron(III) models of ToMOH and the theoretically computed Mössbauer spectra. It also helps explain the formation of two distinct peroxodiiron(III) species in the T201S mutant of ToMOH. Additionally, a role for the ToMOD regulatory protein, which is essential for intermediate formation and protein functioning in the ToMO system, is advanced. We find that the low quadrupole splitting parameter in the Mössbauer spectrum observed for a ToMOH(peroxo) intermediate can be explained by protonation of the peroxo moiety, possibly stabilized by the T201 residue. Finally, similarities between the oxygen activation mechanisms of the monooxygenases and cytochrome P450 are discussed.
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Abstract
The controlled oxidation of methane to methanol is a chemical transformation of great value, particularly in the pursuit of alternative fuels, but the reaction remains underutilized industrially because of inefficient and costly synthetic procedures. In contrast, methane monooxygenase enzymes (MMOs) from methanotrophic bacteria achieve this chemistry efficiently under ambient conditions. In this Account, we discuss the first observable step in the oxidation of methane at the carboxylate-bridged diiron active site of the soluble MMO (sMMO), namely, the reductive activation of atmospheric O(2). The results provide benchmarks against which the dioxygen activation mechanisms of other bacterial multicomponent monooxygenases can be measured. Molecular oxygen reacts rapidly with the reduced diiron(II) cen-ter of the hydroxylase component of sMMO (MMOH). The first spectroscopically characterized intermediate that results from this process is a peroxodiiron(III) species, P*, in which the iron atoms have identical environments. P* converts to a second peroxodiiron(III) unit, H(peroxo), in a process accompanied by the transfer of a proton, probably with the assistance of a residue near the active site. Proton-promoted O-O bond scission and rearrangement of the diiron core then leads to a diiron(IV) unit, termed Q, that is directly responsible for the oxidation of methane to methanol. In one section of this Account, we provide a detailed discussion of these processes, with particular emphasis on possible structures of the intermediates. The geometries of P* and H(peroxo) are currently unknown, and recent synthetic modeling chemistry has highlighted the need for further structural characterization of Q, currently assigned as a di(μ-oxo)diiron(IV) "diamond core." In another section of the Account, we discuss in detail proton transfer during the O(2) activation events. The role of protons in promoting O-O bond cleavage, thereby initiating the conversion of H(peroxo) to Q, was previously a controversial topic. Recent studies of the mechanism, covering a range of pH values and in D(2)O instead of H(2)O, confirmed conclusively that the transfer of protons, possibly at or near the active site, is necessary for both P*-to-H(peroxo) and H(peroxo)-to-Q conversions. Specific mechanistic insights into these processes are provided. In the final section of the Account, we present our view of experiments that need to be done to further define crucial aspects of sMMO chemistry. Here our goal is to detail the challenges that we and others face in this research, particularly with respect to some long-standing questions about the system, as well as approaches that might be used to solve them.
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Affiliation(s)
- Christine E. Tinberg
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
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Platter E, Lawson M, Marsh C, Sazinsky MH. Characterization of a non-ribosomal peptide synthetase-associated diiron arylamine N-oxygenase from Pseudomonas syringae pv. phaseolicola. Arch Biochem Biophys 2011; 508:39-45. [DOI: 10.1016/j.abb.2011.01.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 01/10/2011] [Accepted: 01/12/2011] [Indexed: 11/16/2022]
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66
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Tinberg CE, Song WJ, Izzo V, Lippard SJ. Multiple roles of component proteins in bacterial multicomponent monooxygenases: phenol hydroxylase and toluene/o-xylene monooxygenase from Pseudomonas sp. OX1. Biochemistry 2011; 50:1788-98. [PMID: 21366224 PMCID: PMC3059347 DOI: 10.1021/bi200028z] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phenol hydroxylase (PH) and toluene/o-xylene monooxygenase (ToMO) from Pseudomonas sp. OX1 require three or four protein components to activate dioxygen for the oxidation of aromatic substrates at a carboxylate-bridged diiron center. In this study, we investigated the influence of the hydroxylases, regulatory proteins, and electron-transfer components of these systems on substrate (phenol; NADH) consumption and product (catechol; H(2)O(2)) generation. Single-turnover experiments revealed that only complete systems containing all three or four protein components are capable of oxidizing phenol, a major substrate for both enzymes. Under ideal conditions, the hydroxylated product yield was ∼50% of the diiron centers for both systems, suggesting that these enzymes operate by half-sites reactivity mechanisms. Single-turnover studies indicated that the PH and ToMO electron-transfer components exert regulatory effects on substrate oxidation processes taking place at the hydroxylase actives sites, most likely through allostery. Steady state NADH consumption assays showed that the regulatory proteins facilitate the electron-transfer step in the hydrocarbon oxidation cycle in the absence of phenol. Under these conditions, electron consumption is coupled to H(2)O(2) formation in a hydroxylase-dependent manner. Mechanistic implications of these results are discussed.
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Affiliation(s)
- Christine E. Tinberg
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Woon Ju Song
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Viviana Izzo
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
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67
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Annese C, D’Accolti L, Fusco C, Curci R. Selective Hydroxylation of Methane by Dioxiranes under Mild Conditions. Org Lett 2011; 13:2142-4. [DOI: 10.1021/ol2004676] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Cosimo Annese
- Dipartimento Chimica, CNR-ICCOM, Università di Bari “A. Moro”, v. Amendola 173, 70126 Bari, Italy, and Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Lucia D’Accolti
- Dipartimento Chimica, CNR-ICCOM, Università di Bari “A. Moro”, v. Amendola 173, 70126 Bari, Italy, and Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Caterina Fusco
- Dipartimento Chimica, CNR-ICCOM, Università di Bari “A. Moro”, v. Amendola 173, 70126 Bari, Italy, and Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Ruggero Curci
- Dipartimento Chimica, CNR-ICCOM, Università di Bari “A. Moro”, v. Amendola 173, 70126 Bari, Italy, and Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
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68
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Makhlynets OV, Rybak-Akimova EV. Aromatic hydroxylation at a non-heme iron center: observed intermediates and insights into the nature of the active species. Chemistry 2011; 16:13995-4006. [PMID: 21117047 DOI: 10.1002/chem.201002577] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe(II)(bpmen)(CH(3)CN)(2)][ClO(4)](2) (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2-diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H(2)O(2), although its mechanism of action remains largely unknown. Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H(2)O(2) in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key Fe(III)(OOH) intermediate (λ(max)=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H(2)O(2). Stopped-flow kinetic studies showed that Fe(III)(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated Fe(IV)=O species, which may originate from O-O bond homolysis in Fe(III)(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
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Affiliation(s)
- Olga V Makhlynets
- Department of Chemistry, Tufts University, 62 Talbot Ave., Medford, MA 02155, USA
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69
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Song WJ, McCormick MS, Behan RK, Sazinsky MH, Jiang W, Lin J, Krebs C, Lippard SJ. Active site threonine facilitates proton transfer during dioxygen activation at the diiron center of toluene/o-xylene monooxygenase hydroxylase. J Am Chem Soc 2011; 132:13582-5. [PMID: 20839885 DOI: 10.1021/ja1063795] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Toluene/o-xylene monooxygenase hydroxylase (ToMOH), a diiron-containing enzyme, can activate dioxygen to oxidize aromatic substrates. To elucidate the role of a strictly conserved T201 residue during dioxygen activation of the enzyme, T201S, T201G, T201C, and T201V variants of ToMOH were prepared by site-directed mutagenesis. X-ray crystal structures of all the variants were obtained. Steady-state activity, regiospecificity, and single-turnover yields were also determined for the T201 mutants. Dioxygen activation by the reduced T201 variants was explored by stopped-flow UV-vis and Mössbauer spectroscopy. These studies demonstrate that the dioxygen activation mechanism is preserved in all T201 variants; however, both the formation and decay kinetics of a peroxodiiron(III) intermediate, T201(peroxo), were greatly altered, revealing that T201 is critically involved in dioxygen activation. A comparison of the kinetics of O(2) activation in the T201S, T201C, and T201G variants under various reaction conditions revealed that T201 plays a major role in proton transfer, which is required to generate the peroxodiiron(III) intermediate. A mechanism is postulated for dioxygen activation, and possible structures of oxygenated intermediates are discussed.
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Affiliation(s)
- Woon Ju Song
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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70
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De Hont RF, Xue G, Hendrich MP, Que L, Bominaar EL, Münck E. Mössbauer, electron paramagnetic resonance, and density functional theory studies of synthetic S = 1/2 Fe(III)-O-Fe(IV)═O complexes. Superexchange-mediated spin transition at the Fe(IV)═O site. Inorg Chem 2011; 49:8310-22. [PMID: 20795646 DOI: 10.1021/ic100870v] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Previously we have characterized two high-valent complexes [LFe(IV)(μ-O)(2)Fe(III)L], 1, and [LFe(IV)(O)(μ-O)(OH) Fe(IV)L], 4. Addition of hydroxide or fluoride to 1 produces two new complexes, 1-OH and 1-F. Electron paramagnetic resonance (EPR) and Mössbauer studies show that both complexes have an S = 1/2 ground state which results from antiferromagnetic coupling of the spins of a high-spin (S(a) = 5/2) Fe(III) and a high-spin (S(b) = 2) Fe(IV) site. 1-OH can also be obtained by a 1-electron reduction of 4, which has been shown to have an Fe(IV)═O site. Radiolytic reduction of 4 at 77 K yields a Mössbauer spectrum identical to that observed for 1-OH, showing that the latter contains an Fe(IV)═O. Interestingly, the Fe(IV)═O moiety has S(b) = 1 in 4 and S(b) = 2 in 1-OH and 1-F. From the temperature dependence of the S = 1/2 signal we have determined the exchange coupling constant J (ℋ = JS(a)·S(b) convention) to be 90 ± 20 cm(-1) for both 1-OH and 1-F. Broken-symmetry density functional theory (DFT) calculations yield J = 135 cm(-1) for 1-OH and J = 104 cm(-1) for 1-F, in good agreement with the experiments. DFT analysis shows that the S(b) = 1 → S(b) = 2 transition of the Fe(IV)═O site upon reduction of the Fe(IV)-OH site to high-spin Fe(III) is driven primarily by the strong antiferromagnetic exchange in the (S(a) = 5/2, S(b) = 2) couple.
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Affiliation(s)
- Raymond F De Hont
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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71
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Izzo V, Leo G, Scognamiglio R, Troncone L, Birolo L, Di Donato A. PHK from phenol hydroxylase of Pseudomonas sp. OX1. Insight into the role of an accessory protein in bacterial multicomponent monooxygenases. Arch Biochem Biophys 2011; 505:48-59. [DOI: 10.1016/j.abb.2010.09.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 09/06/2010] [Accepted: 09/25/2010] [Indexed: 11/30/2022]
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72
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Shaik S, Chen H, Janardanan D. Exchange-enhanced reactivity in bond activation by metal-oxo enzymes and synthetic reagents. Nat Chem 2010; 3:19-27. [PMID: 21160512 DOI: 10.1038/nchem.943] [Citation(s) in RCA: 263] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Reactivity principles based on orbital overlap and bonding/antibonding interactions are well established to describe the reactivity of organic species, and atomic structures are typically predicted by Hund's rules to have maximum single-electron occupancy of degenerate orbitals in the ground state. Here, we extend the role of exchange to transition states and discuss how, for reactions and kinetics of bioinorganic species, the analogue of Hund's rules is exchange-controlled reactivity. Pathways that increase the number of unpaired and spin-identical electrons on a metal centre will be favoured by exchange stabilization. Such exchange-enhanced reactivity endows transition states with a stereochemistry different from that observed in cases that are not exchange-enhanced, and is in good agreement with the reactivity observed for iron-based enzymes and synthetic analogues. We discuss the interplay between orbital- and exchange-controlled principles, and how this depends on the identity of the transition metal, its oxidation number and its coordination sphere.
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Affiliation(s)
- Sason Shaik
- Institute of Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
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73
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Bacterial phenylalanine and phenylacetate catabolic pathway revealed. Proc Natl Acad Sci U S A 2010; 107:14390-5. [PMID: 20660314 DOI: 10.1073/pnas.1005399107] [Citation(s) in RCA: 270] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Aromatic compounds constitute the second most abundant class of organic substrates and environmental pollutants, a substantial part of which (e.g., phenylalanine or styrene) is metabolized by bacteria via phenylacetate. Surprisingly, the bacterial catabolism of phenylalanine and phenylacetate remained an unsolved problem. Although a phenylacetate metabolic gene cluster had been identified, the underlying biochemistry remained largely unknown. Here we elucidate the catabolic pathway functioning in 16% of all bacteria whose genome has been sequenced, including Escherichia coli and Pseudomonas putida. This strategy is exceptional in several aspects. Intermediates are processed as CoA thioesters, and the aromatic ring of phenylacetyl-CoA becomes activated to a ring 1,2-epoxide by a distinct multicomponent oxygenase. The reactive nonaromatic epoxide is isomerized to a seven-member O-heterocyclic enol ether, an oxepin. This isomerization is followed by hydrolytic ring cleavage and beta-oxidation steps, leading to acetyl-CoA and succinyl-CoA. This widespread paradigm differs significantly from the established chemistry of aerobic aromatic catabolism, thus widening our view of how organisms exploit such inert substrates. It provides insight into the natural remediation of man-made environmental contaminants such as styrene. Furthermore, this pathway occurs in various pathogens, where its reactive early intermediates may contribute to virulence.
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74
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Friedle S, Reisner E, Lippard SJ. Current challenges of modeling diiron enzyme active sites for dioxygen activation by biomimetic synthetic complexes. Chem Soc Rev 2010; 39:2768-79. [PMID: 20485834 DOI: 10.1039/c003079c] [Citation(s) in RCA: 221] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This tutorial review describes recent progress in modeling the active sites of carboxylate-rich non-heme diiron enzymes that activate dioxygen to carry out several key reactions in Nature. The chemistry of soluble methane monooxygenase, which catalyzes the selective oxidation of methane to methanol, is of particular interest for (bio)technological applications. Novel synthetic diiron complexes that mimic structural, and, to a lesser extent, functional features of these diiron enzymes are discussed. The chemistry of the enzymes is also briefly summarized. A particular focus of this review is on models that mimic characteristics of the diiron systems that were previously not emphasized, including systems that contain (i) aqua ligands, (ii) different substrates tethered to the ligand framework, (iii) dendrimers attached to carboxylates to mimic the protein environment, (iv) two N-donors in a syn-orientation with respect to the iron-iron vector, and (v) a N-rich ligand environment capable of accessing oxygenated high-valent diiron intermediates.
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Affiliation(s)
- Simone Friedle
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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75
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Rather LJ, Knapp B, Haehnel W, Fuchs G. Coenzyme A-dependent aerobic metabolism of benzoate via epoxide formation. J Biol Chem 2010; 285:20615-24. [PMID: 20452977 DOI: 10.1074/jbc.m110.124156] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the aerobic metabolism of aromatic substrates, oxygenases use molecular oxygen to hydroxylate and finally cleave the aromatic ring. In the case of the common intermediate benzoate, the ring cleavage substrates are either catechol (in bacteria) or 3,4-dihydroxybenzoate (protocatechuate, mainly in fungi). We have shown before that many bacteria, e.g. Azoarcus evansii, the organism studied here, use a completely different mechanism. This elaborate pathway requires formation of benzoyl-CoA, followed by an oxygenase reaction and a nonoxygenolytic ring cleavage. Benzoyl-CoA transformation is catalyzed by the iron-containing benzoyl-CoA oxygenase (BoxB) in conjunction with an FAD and iron-sulfur centers containing reductase (BoxA), which donates electrons from NADPH. Here we show that benzoyl-CoA oxygenase actually does not form the 2,3-dihydrodiol of benzoyl-CoA, as formerly postulated, but the 2,3-epoxide. An enoyl-CoA hydratase (BoxC) uses two molecules of water to first hydrolytically open the ring of 2,3-epoxybenzoyl-CoA, which may proceed via its tautomeric seven-membered oxepin ring form. Then ring C2 is hydrolyzed off as formic acid, yielding 3,4-dehydroadipyl-CoA semialdehyde. The semialdehyde is oxidized by a NADP(+)-dependent aldehyde dehydrogenase (BoxD) to 3,4-dehydroadipyl-CoA. Final products of the pathway are formic acid, acetyl-CoA, and succinyl-CoA. This overlooked pathway occurs in 4-5% of all bacteria whose genomes have been sequenced and represents an elegant strategy to cope with the high resonance energy of aromatic substrates by forming a nonaromatic epoxide.
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Affiliation(s)
- Liv J Rather
- Lehrstuhl Mikrobiologie, Fakultät Biologie, Schänzlestrasse 1, Universität Freiburg, D-79104 Freiburg, Germany
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76
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Alonso D, Nájera C, Pastor I, Yus M. Transition-Metal-Catalyzed Synthesis of Hydroxylated Arenes. Chemistry 2010; 16:5274-84. [DOI: 10.1002/chem.201000470] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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77
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Oppenheimer M, Pierce BS, Crawford JA, Ray K, Helm RF, Sobrado P. Recombinant expression, purification, and characterization of ThmD, the oxidoreductase component of tetrahydrofuran monooxygenase. Arch Biochem Biophys 2010; 496:123-31. [PMID: 20159007 DOI: 10.1016/j.abb.2010.02.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/09/2010] [Accepted: 02/10/2010] [Indexed: 11/29/2022]
Abstract
Tetrahydrofuran monooxygenase (Thm) catalyzes the NADH-and oxygen-dependent hydroxylation of tetrahydrofuran to 2-hydroxytetrahydrofuran. Thm is composed of a hydroxylase enzyme, a regulatory subunit, and an oxidoreductase named ThmD. ThmD was expressed in Escherichia coli as a fusion to maltose-binding protein (MBP) and isolated to homogeneity after removal of the MBP. Purified ThmD contains covalently bound FAD, [2Fe-2S] center, and was shown to use ferricyanide, cytochrome c, 2,6-dichloroindophenol, and to a lesser extent, oxygen as surrogate electron acceptors. ThmD displays 160-fold preference for NADH over NADPH and functions as a monomer. The flavin-binding domain of ThmD (ThmD-FD) was purified and characterized. ThmD-FD displayed similar activity as the full-length ThmD and showed a unique flavin spectrum with a major peak at 463nm and a small peak at 396 nm. Computational modeling and mutagenesis analyses suggest a novel three-dimensional fold or covalent flavin attachment in ThmD.
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78
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Makhlynets OV, Das P, Taktak S, Flook M, Mas-Ballesté R, Rybak-Akimova EV, Que L. Iron-promoted ortho- and/or ipso-hydroxylation of benzoic acids with H(2)O(2). Chemistry 2010; 15:13171-80. [PMID: 19876966 DOI: 10.1002/chem.200901296] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Regioselective hydroxylation of aromatic acids with hydrogen peroxide proceeds readily in the presence of iron(II) complexes with tetradentate aminopyridine ligands [Fe(II)(BPMEN)(CH(3)CN)(2)](ClO(4))(2) (1) and [Fe(II)(TPA)(CH(3)CN)(2)](OTf)(2) (2), where BPMEN=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-ethylenediamine, TPA=tris-(2-pyridylmethyl)amine. Two cis-sites, which are occupied by labile acetonitrile molecules in 1 and 2, are available for coordination of H(2)O(2) and substituted benzoic acids. The hydroxylation of the aromatic ring occurs exclusively in the vicinity of the anchoring carboxylate functional group: ortho-hydroxylation affords salicylates, whereas ipso-hydroxylation with concomitant decarboxylation yields phenolates. The outcome of the substituent-directed hydroxylation depends on the electronic properties and the position of substituents in the molecules of substrates: 3-substituted benzoic acids are preferentially ortho-hydroxylated, whereas 2- and, to a lesser extent, 4-substituted substrates tend to undergo ipso-hydroxylation/decarboxylation. These two pathways are not mutually exclusive and likely proceed via a common intermediate. Electron-withdrawing substituents on the aromatic ring of the carboxylic acids disfavor hydroxylation, indicating an electrophilic nature for the active oxidant. Complexes 1 and 2 exhibit similar reactivity patterns, but 1 generates a more powerful oxidant than 2. Spectroscopic and labeling studies exclude acylperoxoiron(III) and Fe(IV)=O species as potential reaction intermediates, but strongly indicate the involvement of an Fe(III)--OOH intermediate that undergoes intramolecular acid-promoted heterolytic O-O bond cleavage, producing a transient iron(V) oxidant.
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Affiliation(s)
- Olga V Makhlynets
- Department of Chemistry, Tufts University, 62 Talbot Ave., Medford, MA 02155, USA
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79
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Jarenmark M, Turitsyna EA, Haukka M, Shteinman AA, Nordlander E. A monocarboxylate-bridged diiron(iii) μ-oxido complex that catalyzes alkane oxidation by hydrogen peroxide. NEW J CHEM 2010. [DOI: 10.1039/c0nj00293c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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80
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Tinberg CE, Lippard SJ. Revisiting the mechanism of dioxygen activation in soluble methane monooxygenase from M. capsulatus (Bath): evidence for a multi-step, proton-dependent reaction pathway. Biochemistry 2009; 48:12145-58. [PMID: 19921958 PMCID: PMC2797563 DOI: 10.1021/bi901672n] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Stopped-flow kinetic investigations of soluble methane monooxygenase (sMMO) from M. capsulatus (Bath) have clarified discrepancies that exist in the literature regarding several aspects of catalysis by this enzyme. The development of thorough kinetic analytical techniques has led to the discovery of two novel oxygenated iron species that accumulate in addition to the well-established intermediates H(peroxo) and Q. The first intermediate, P*, is a precursor to H(peroxo) and was identified when the reaction of reduced MMOH and MMOB with O(2) was carried out in the presence of >or=540 microM methane to suppress the dominating absorbance signal due to Q. The optical properties of P* are similar to those of H(peroxo), with epsilon(420) = 3500 M(-1) cm(-1) and epsilon(720) = 1250 M(-1) cm(-1). These values are suggestive of a peroxo-to-iron(III) charge-transfer transition and resemble those of peroxodiiron(III) intermediates characterized in other carboxylate-bridged diiron proteins and synthetic model complexes. The second identified intermediate, Q*, forms on the pathway of Q decay when reactions are performed in the absence of hydrocarbon substrate. Q* does not react with methane, forms independently of buffer composition, and displays a unique shoulder at 455 nm in its optical spectrum. Studies conducted at different pH values reveal that rate constants corresponding to P* decay/H(peroxo) formation and H(peroxo) decay/Q formation are both significantly retarded at high pH and indicate that both events require proton transfer. The processes exhibit normal kinetic solvent isotope effects (KSIEs) of 2.0 and 1.8, respectively, when the reactions are performed in D(2)O. Mechanisms are proposed to account for the observations of these novel intermediates and the proton dependencies of P* to H(peroxo) and H(peroxo) to Q conversion.
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Affiliation(s)
| | - Stephen J. Lippard
- To whom correspondence should be addressed.
. Telephone: (617) 253-1892. Fax: (617)
258-8150
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81
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Frisch JR, Vu VV, Martinho M, Münck E, Que L. Characterization of two distinct adducts in the reaction of a nonheme diiron(II) complex with O2. Inorg Chem 2009; 48:8325-36. [PMID: 19610611 DOI: 10.1021/ic900961k] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two [Fe(II)(2)(N-EtHPTB)(mu-O(2)X)](2+) complexes, where N-EtHPTB is the anion of N,N,N'N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diaminopropane and O(2)X is O(2)PPh(2) (1 x O(2)PPh(2)) or O(2)AsMe(2) (1 x O(2)AsMe(2)), have been synthesized. Their crystal structures both show interiron distances of 3.54 A that arise from a (mu-alkoxo)diiron(II) core supported by an O(2)X bridge. These diiron(II) complexes react with O(2) at low temperatures in MeCN (-40 degrees C) and CH(2)Cl(2) (-60 degrees C) to form long-lived O(2) adducts that are best described as (mu-eta(1):eta(1)-peroxo)diiron(III) species (2 x O(2)X) with nu(O-O) approximately 850 cm(-1). Upon warming to -30 degrees C, 2 x O(2)PPh(2) converts irreversibly to a second (mu-eta(1):eta(1)-peroxo)diiron(III) intermediate (3 x O(2)PPh(2)) with nu(O-O) approximately 900 cm(-1), a value which matches that reported for [Fe(2)(N-EtHPTB)(O(2))(O(2)CPh)](2+) (3 x O(2)CPh) (Dong et al. J. Am. Chem. Soc. 1993, 115, 1851-1859). Mossbauer spectra of 2 x O(2)PPh(2) and 3 x O(2)PPh(2) indicate that the iron centers within each species are antiferromagnetically coupled with J approximately 60 cm(-1), while extended X-ray absorption fine structure analysis reveals interiron distances of 3.25 and 3.47 A for 2 x O(2)PPh(2) and 3 x O(2)PPh(2), respectively. A similarly short interiron distance (3.27 A) is found for 2 x O(2)AsMe(2). The shorter interiron distance associated with 2 x O(2)PPh(2) and 2 x O(2)AsMe(2) is proposed to derive from a triply bridged diiron(III) species with alkoxo (from N-EtHPTB), 1,2-peroxo, and 1,3-O(2)X bridges, while the longer distance associated with 3 x O(2)PPh(2) results from the shift of the O(2)PPh(2) bridge to a terminal position on one iron. The differences in nu(O-O) are also consistent with the different interiron distances. It is suggested that the O...O bite distance of the O(2)X moiety affects the thermal stability of 2 x O(2)X, with the O(2)X having the largest bite distance (O(2)AsMe(2)) favoring the 2 x O(2)X adduct and the O(2)X having the smallest bite distance (O(2)CPh) favoring the 3 x O(2)X adduct. Interestingly, neither 3 x O(2)AsMe(2) nor the benzoate analog of 2 x O(2)X (2 x O(2)Bz) are observed.
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Affiliation(s)
- Jonathan R Frisch
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. S.E., Minneapolis, Minnesota 55455, USA
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82
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Friedle S, Kodanko JJ, Morys AJ, Hayashi T, Moënne-Loccoz P, Lippard SJ. Modeling the syn disposition of nitrogen donors in non-heme diiron enzymes. Synthesis, characterization, and hydrogen peroxide reactivity of diiron(III) complexes with the syn N-donor ligand H2BPG2DEV. J Am Chem Soc 2009; 131:14508-20. [PMID: 19757795 DOI: 10.1021/ja906137y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In order to model the syn disposition of histidine residues in carboxylate-bridged non-heme diiron enzymes, we prepared a new dinucleating ligand, H(2)BPG(2)DEV, that provides this geometric feature. The ligand incorporates biologically relevant carboxylate functionalities, which have not been explored as extensively as nitrogen-only analogues. Three novel oxo-bridged diiron(III) complexes, [Fe(2)(mu-O)(H(2)O)(2)(BPG(2)DEV)](ClO(4))(2) (6), [Fe(2)(mu-O)(mu-O(2)CAr(iPrO))(BPG(2)DEV)](ClO(4)) (7), and [Fe(2)(mu-O)(mu-CO(3))(BPG(2)DEV)] (8), were prepared. Single-crystal X-ray structural characterization confirms that two pyridyl groups are bound syn with respect to the Fe-Fe vector in these compounds. The carbonato-bridged complex 8 forms quantitatively from 6 in a rapid reaction with gaseous CO(2) in organic solvents. A common maroon-colored intermediate (lambda(max) = 490 nm; epsilon = 1500 M(-1) cm(-1)) forms in reactions of 6, 7, or 8 with H(2)O(2) and NEt(3) in CH(3)CN/H(2)O solutions. Mass spectrometric analyses of this species, formed using (18)O-labeled H(2)O(2), indicate the presence of a peroxide ligand bound to the oxo-bridged diiron(III) center. The Mossbauer spectrum at 90 K of the EPR-silent intermediate exhibits a quadrupole doublet with delta = 0.58 mm/s and DeltaE(Q) = 0.58 mm/s. The isomer shift is typical for a peroxodiiron(III) species, but the quadrupole splitting parameter is unusually small compared to those of related complexes. These Mossbauer parameters are comparable to those observed for a peroxo intermediate formed in the reaction of reduced toluene/o-xylene monooxygenase hydroxylase with dioxygen. Resonance Raman studies reveal an unusually low-energy O-O stretching mode in the peroxo intermediate that is consistent with a short diiron distance. Although peroxodiiron(III) intermediates generated from 6, 7, and 8 are poor O-atom-transfer catalysts, they display highly efficient catalase activity, with turnover numbers up to 10,000. In contrast to hydrogen peroxide reactions of diiron(III) complexes that lack a dinucleating ligand, the intermediates generated here could be re-formed in significant quantities after a second addition of H(2)O(2), as observed spectroscopically and by mass spectrometry.
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Affiliation(s)
- Simone Friedle
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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83
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Friedle S, Lippard SJ. Synthesis, Characterization, and Oxygenation Studies of Carboxylate-Bridged Diiron(II) Complexes with Aromatic Substrates Tethered to Pyridine Ligands and the Formation of a Unique Trinuclear Complex. Eur J Inorg Chem 2009; 2009:5506-5515. [PMID: 20376288 DOI: 10.1002/ejic.200900821] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this study, diiron(II) complexes were synthesized as small molecule mimics of the reduced active sites in the hydroxylase components of bacterial multicomponent monooxygenases (BMMs). Tethered aromatic substrates were introduced in the form of 2-phenoxypyridines, incorporating hydroxy and methoxy functionalities into windmill-type diiron(II) compounds [Fe(2)(μ-O(2)CAr(R))(2)-(O(2)CAr(R))(2)(L)(2)] (1-4), where (-)O(2)CAr(R) is a sterically encumbering carboxylate, 2,6-di(4-fluorophenyl)- or 2,6-di(p-tolyl)benzoate (R = 4-FPh or Tol, respectively). The inability of 1-4 to hydroxylate the aromatic substrates was ascertained. Upon reaction with dioxygen, compounds 2 and 3 (L = 2-(m-MeOPhO)Py, 2-(p-MeOPhO)Py, respectively) decompose by a known bimolecular pathway to form mixed-valent diiron(II,III) species at low temperature. Use of 2-(pyridin-2-yloxy)phenol as the ligand L resulted in a doubly-bridged diiron complex (4) and an unprecedented phenoxide-bridged triiron(II) complex (5) under slightly modified reaction conditions.
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Affiliation(s)
- Simone Friedle
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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84
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Xin Y, Gadda G, Hamelberg D. The Cluster of Hydrophobic Residues Controls the Entrance to the Active Site of Choline Oxidase. Biochemistry 2009; 48:9599-605. [DOI: 10.1021/bi901295a] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Giovanni Gadda
- Department of Chemistry
- Department of Biology
- The Center for Biotechnology and Drug Design
| | - Donald Hamelberg
- Department of Chemistry
- The Center for Biotechnology and Drug Design
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85
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Oxidation Reactivity of Bis(μ-oxo) Dinickel(III) Complexes: Arene Hydroxylation of the Supporting Ligand. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200900222] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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86
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Honda K, Cho J, Matsumoto T, Roh J, Furutachi H, Tosha T, Kubo M, Fujinami S, Ogura T, Kitagawa T, Suzuki M. Oxidation Reactivity of Bis(μ-oxo) Dinickel(III) Complexes: Arene Hydroxylation of the Supporting Ligand. Angew Chem Int Ed Engl 2009; 48:3304-7. [DOI: 10.1002/anie.200900222] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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87
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Elsen NL, Bailey LJ, Hauser AD, Fox BG. Role for Threonine 201 in the Catalytic Cycle of the Soluble Diiron Hydroxylase Toluene 4-Monooxygenase,. Biochemistry 2009; 48:3838-46. [DOI: 10.1021/bi900144a] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Nathaniel L. Elsen
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706-1544
| | - Lucas J. Bailey
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706-1544
| | - Andrew D. Hauser
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706-1544
| | - Brian G. Fox
- Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706-1544
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88
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Ukaegbu UE, Rosenzweig AC. Structure of the redox sensor domain of Methylococcus capsulatus (Bath) MmoS. Biochemistry 2009; 48:2207-15. [PMID: 19271777 PMCID: PMC2707821 DOI: 10.1021/bi8019614] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
MmoS from Methylococcus capsulatus (Bath) is the multidomain sensor protein of a two-component signaling system proposed to play a role in the copper-mediated regulation of soluble methane monooxygenase (sMMO). MmoS binds an FAD cofactor within its N-terminal tandem Per-Arnt-Sim (PAS) domains, suggesting that it functions as a redox sensor. The crystal structure of the MmoS tandem PAS domains, designated PAS-A and PAS-B, has been determined to 2.34 A resolution. Both domains adopt the typical PAS domain alpha/beta topology and are structurally similar. The two domains are linked by a long alpha helix and do not interact with one another. The FAD cofactor is housed solely within PAS-A and is stabilized by an extended hydrogen bonding network. The overall fold of PAS-A is similar to those of other flavin-containing PAS domains, but homodimeric interactions in other structures are not observed in the MmoS sensor, which crystallized as a monomer. The structure both provides new insight into the architecture of tandem PAS domains and suggests specific residues that may play a role in MmoS FAD redox chemistry and subsequent signal transduction.
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Affiliation(s)
- Uchechi E. Ukaegbu
- Departments of Biochemistry, Molecular Biology and Cell Biology and of Chemistry, Northwestern University, Evanston, IL 60208
| | - Amy C. Rosenzweig
- Departments of Biochemistry, Molecular Biology and Cell Biology and of Chemistry, Northwestern University, Evanston, IL 60208
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89
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Abstract
pMMO (particulate methane mono-oxygenase) is an integral membrane metalloenzyme that catalyses the oxidation of methane to methanol. The pMMO metal active site has not been identified, precluding detailed investigation of the reaction mechanism. Models for the metal centres proposed by various research groups have evolved as crystallographic and spectroscopic data have become available. The present review traces the evolution of these active-site models before and after the 2005 Methylococcus capsulatus (Bath) pMMO crystal structure determination.
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90
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Afanasiev P, Bouchu D, Kudrik EV, Millet JMM, Sorokin AB. Stable N-bridged diiron (IV) phthalocyanine cation radical complexes: synthesis and properties. Dalton Trans 2009:9828-36. [DOI: 10.1039/b916047g] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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91
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Molecular determinants of the regioselectivity of toluene/o-xylene monooxygenase from Pseudomonas sp. strain OX1. Appl Environ Microbiol 2008; 75:823-36. [PMID: 19074607 DOI: 10.1128/aem.01951-08] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial multicomponent monooxygenases (BMMs) are a heterogeneous family of di-iron monooxygenases which share the very interesting ability to hydroxylate aliphatic and/or aromatic hydrocarbons. Each BMM possesses defined substrate specificity and regioselectivity which match the metabolic requirements of the strain from which it has been isolated. Pseudomonas sp. strain OX1, a strain able to metabolize o-, m-, and p-cresols, produces the BMM toluene/o-xylene monooxygenase (ToMO), which converts toluene to a mixture of o-, m-, and p-cresol isomers. In order to investigate the molecular determinants of ToMO regioselectivity, we prepared and characterized 15 single-mutant and 3 double-mutant forms of the ToMO active site pocket. Using the Monte Carlo approach, we prepared models of ToMO-substrate and ToMO-reaction intermediate complexes which allowed us to provide a molecular explanation for the regioselectivities of wild-type and mutant ToMO enzymes. Furthermore, using binding energy values calculated by energy analyses of the complexes and a simple mathematical model of the hydroxylation reaction, we were able to predict quantitatively the regioselectivities of the majority of the variant proteins with good accuracy. The results show not only that the fine-tuning of ToMO regioselectivity can be achieved through a careful alteration of the shape of the active site but also that the effects of the mutations on regioselectivity can be quantitatively predicted a priori.
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92
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Bailey LJ, McCoy JG, Phillips GN, Fox BG. Structural consequences of effector protein complex formation in a diiron hydroxylase. Proc Natl Acad Sci U S A 2008; 105:19194-8. [PMID: 19033467 PMCID: PMC2614738 DOI: 10.1073/pnas.0807948105] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Indexed: 11/18/2022] Open
Abstract
Carboxylate-bridged diiron hydroxylases are multicomponent enzyme complexes responsible for the catabolism of a wide range of hydrocarbons and as such have drawn attention for their mechanism of action and potential uses in bioremediation and enzymatic synthesis. These enzyme complexes use a small molecular weight effector protein to modulate the function of the hydroxylase. However, the origin of these functional changes is poorly understood. Here, we report the structures of the biologically relevant effector protein-hydroxylase complex of toluene 4-monooxygenase in 2 redox states. The structures reveal a number of coordinated changes that occur up to 25 A from the active site and poise the diiron center for catalysis. The results provide a structural basis for the changes observed in a number of the measurable properties associated with effector protein binding. This description provides insight into the functional role of effector protein binding in all carboxylate-bridged diiron hydroxylases.
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Affiliation(s)
- Lucas J. Bailey
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706-1544
| | - Jason G. McCoy
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706-1544
| | - George N. Phillips
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706-1544
| | - Brian G. Fox
- Department of Biochemistry, University of Wisconsin, 433 Babcock Drive, Madison, WI 53706-1544
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93
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Simmons JM, Müller TA, Hausinger RP. Fe(II)/alpha-ketoglutarate hydroxylases involved in nucleobase, nucleoside, nucleotide, and chromatin metabolism. Dalton Trans 2008:5132-42. [PMID: 18813363 PMCID: PMC2907160 DOI: 10.1039/b803512a] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fe(II)/alpha-ketoglutarate-dependent hydroxylases uniformly possess a double-stranded beta-helix fold with two conserved histidines and one carboxylate coordinating their mononuclear ferrous ions. Oxidative decomposition of the alpha-keto acid is proposed to generate a ferryl-oxo intermediate capable of hydroxylating unactivated carbon atoms in a myriad of substrates. This Perspective focuses on a subgroup of these enzymes that are involved in pyrimidine salvage, purine decomposition, nucleoside and nucleotide hydroxylation, DNA/RNA repair, and chromatin modification. The varied reaction schemes are presented, and selected structural and kinetic information is summarized.
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Affiliation(s)
- Jana M. Simmons
- Department of Biochemistry and Molecular Biology, 6193 Biomedical Physical Sciences Bldg, Michigan State University, East Lansing, Michigan, USA, 48824-4320
| | - Tina A. Müller
- Department of Microbiology and Molecular Genetics, 6193 Biomedical Physical Sciences Bldg, Michigan State University, East Lansing, Michigan, USA, 48824-4320
| | - Robert P. Hausinger
- Department of Biochemistry and Molecular Biology, 6193 Biomedical Physical Sciences Bldg, Michigan State University, East Lansing, Michigan, USA, 48824-4320
- Department of Microbiology and Molecular Genetics, 6193 Biomedical Physical Sciences Bldg, Michigan State University, East Lansing, Michigan, USA, 48824-4320
- Quantitative Biology Program, 6193 Biomedical Physical Sciences Bldg, Michigan State University, East Lansing, Michigan, USA, 48824-4320
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94
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de Visser SP, Lee YM, Nam W. Theoretical Investigation on the Mechanism of Oxygen Atom Transfer between Two Non-Heme Iron Centres. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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95
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Jiang H, Stepowska E, Song D. Aerobic oxidation of C(sp3)–H bonds of 4,5-diazafluorene promoted by coordination. Dalton Trans 2008:5879-81. [DOI: 10.1039/b812561a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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96
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97
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Murray LJ, García-Serres R, McCormick MS, Davydov R, Naik S, Kim SH, Hoffman BM, Huynh BH, Lippard SJ. Dioxygen activation at non-heme diiron centers: oxidation of a proximal residue in the I100W variant of toluene/o-xylene monooxygenase hydroxylase. Biochemistry 2007; 46:14795-809. [PMID: 18044971 PMCID: PMC2494530 DOI: 10.1021/bi7017128] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
At its carboxylate-bridged diiron active site, the hydroxylase component of toluene/o-xylene monooxygenase activates dioxygen for subsequent arene hydroxylation. In an I100W variant of this enzyme, we characterized the formation and decay of two species formed by addition of dioxygen to the reduced, diiron(II) state by rapid-freeze quench (RFQ) EPR, Mössbauer, and ENDOR spectroscopy. The dependence of the formation and decay rates of this mixed-valent transient on pH and the presence of phenol, propylene, or acetylene was investigated by double-mixing stopped-flow optical spectroscopy. Modification of the alpha-subunit of the hydroxylase after reaction of the reduced protein with dioxygen-saturated buffer was investigated by tryptic digestion coupled mass spectrometry. From these investigations, we conclude that (i) a diiron(III,IV)-W* transient, kinetically linked to a preceding diiron(III) intermediate, arises from the one-electron oxidation of W100, (ii) the tryptophan radical is deprotonated, (iii) rapid exchange of either a terminal water or hydroxide ion with water occurs at the ferric ion in the diiron(III,IV) cluster, and (iv) the diiron(III,IV) core and W* decay to the diiron(III) product by a common mechanism. No transient radical was observed by stopped-flow optical spectroscopy for reactions of the reduced hydroxylase variants I100Y, L208F, and F205W with dioxygen. The absence of such species, and the deprotonated state of the tryptophanyl radical in the diiron(III,IV)-W* transient, allow for a conservative estimate of the reduction potential of the diiron(III) intermediate as lying between 1.1 and 1.3 V. We also describe the X-ray crystal structure of the I100W variant of ToMOH.
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Affiliation(s)
- Leslie J. Murray
- Department of Chemistry, Massachusetts Institute of Technology Cambridge, MA 02139
| | | | - Michael S. McCormick
- Department of Chemistry, Massachusetts Institute of Technology Cambridge, MA 02139
| | - Roman Davydov
- Department of Chemistry, Northwestern University, Evanston, IL 60208
| | - Sunil Naik
- Department of Physics, Emory University, Atlanta, GA 30322
| | - Sun-Hee Kim
- Department of Chemistry, Northwestern University, Evanston, IL 60208
| | - Brian M. Hoffman
- Department of Chemistry, Northwestern University, Evanston, IL 60208
| | - Boi Hanh Huynh
- Department of Physics, Emory University, Atlanta, GA 30322
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology Cambridge, MA 02139
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98
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Reisner E, Telser J, Lippard SJ. A Planar Carboxylate-Rich Tetrairon(II) Complex and Its Conversion to Linear Triiron(II) and Paddlewheel Diiron(II) Complexes. Inorg Chem 2007; 46:10754-70. [DOI: 10.1021/ic701663j] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Erwin Reisner
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Biological, Chemical, and Physical Sciences, Roosevelt University, 430 S. Michigan Avenue, Chicago, Illinois 60605
| | - Joshua Telser
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Biological, Chemical, and Physical Sciences, Roosevelt University, 430 S. Michigan Avenue, Chicago, Illinois 60605
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, and Department of Biological, Chemical, and Physical Sciences, Roosevelt University, 430 S. Michigan Avenue, Chicago, Illinois 60605
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