151
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A family of diiron monooxygenases catalyzing amino acid beta-hydroxylation in antibiotic biosynthesis. Proc Natl Acad Sci U S A 2010; 107:15391-6. [PMID: 20713732 DOI: 10.1073/pnas.1007953107] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The biosynthesis of chloramphenicol requires a beta-hydroxylation tailoring reaction of the precursor L-p-aminophenylalanine (L-PAPA). Here, it is shown that this reaction is catalyzed by the enzyme CmlA from an operon containing the genes for biosynthesis of L-PAPA and the nonribosomal peptide synthetase CmlP. EPR, Mössbauer, and optical spectroscopies reveal that CmlA contains an oxo-bridged dinuclear iron cluster, a metal center not previously associated with nonribosomal peptide synthetase chemistry. Single-turnover kinetic studies indicate that CmlA is functional in the diferrous state and that its substrate is L-PAPA covalently bound to CmlP. Analytical studies show that the product is hydroxylated L-PAPA and that O(2) is the oxygen source, demonstrating a monooxygenase reaction. The gene sequence of CmlA shows that it utilizes a lactamase fold, suggesting that the diiron cluster is in a protein environment not previously known to effect monooxygenase reactions. Notably, CmlA homologs are widely distributed in natural product biosynthetic pathways, including a variety of pharmaceutically important beta-hydroxylated antibiotics and cytostatics.
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152
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Chung LW, Li X, Sugimoto H, Shiro Y, Morokuma K. ONIOM Study on a Missing Piece in Our Understanding of Heme Chemistry: Bacterial Tryptophan 2,3-Dioxygenase with Dual Oxidants. J Am Chem Soc 2010; 132:11993-2005. [DOI: 10.1021/ja103530v] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Lung Wa Chung
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan, and Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
| | - Xin Li
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan, and Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
| | - Hiroshi Sugimoto
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan, and Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
| | - Yoshitsugu Shiro
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan, and Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
| | - Keiji Morokuma
- Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan, and Biometal Science Laboratory, RIKEN SPring-8 Center, Harima Institute, Hyogo 679-5148, Japan
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153
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Abstract
Whole-cell biocatalysis utilizes native or recombinant enzymes produced by cellular metabolism to perform synthetically interesting reactions. Besides hydrolases, oxidoreductases represent the most applied enzyme class in industry. Oxidoreductases are attributed a high future potential, especially for applications in the chemical and pharmaceutical industries, as they enable highly interesting chemistry (e.g., the selective oxyfunctionalization of unactivated C-H bonds). Redox reactions are characterized by electron transfer steps that often depend on redox cofactors as additional substrates. Their regeneration typically is accomplished via the metabolism of whole-cell catalysts. Traditionally, studies towards productive redox biocatalysis focused on the biocatalytic enzyme, its activity, selectivity, and specificity, and several successful examples of such processes are running commercially. However, redox cofactor regeneration by host metabolism was hardly considered for the optimization of biocatalytic rate, yield, and/or titer. This article reviews molecular mechanisms of oxidoreductases with synthetic potential and the host redox metabolism that fuels biocatalytic reactions with redox equivalents. The tools discussed in this review for investigating redox metabolism provide the basis for studies aiming at a deeper understanding of the interplay between synthetically active enzymes and metabolic networks. The ultimate goal of rational whole-cell biocatalyst engineering and use for fine chemical production is discussed.
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154
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Abstract
Coordination to transition-metal complexes changes both the thermodynamics and kinetics of oxygen reduction. Some of the intermediates (superoxo, hydroperoxo, and oxo species) are close analogues of organic oxygen-centered radicals and peroxides (ROO(*), ROOH, and RO(*)). Metal-based intermediates are typically less reactive, but more persistent, than organic radicals, which makes the two types of intermediates similarly effective in their reactions with various substrates. The self-exchange rate constant for hydrogen-atom transfer for the couples Cr(aq)OO(2+)/Cr(aq)OOH(2+) and L(1)(H(2)O)RhOO(2+)/L(1)(H(2)O)RhOOH(2+) was estimated to be 10(1+/-1) M(-1) s(-1). The use of this value in the simplified Marcus equation for the Cr(aq)O(2+)/Cr(aq)OOH(2+) cross reaction provided an upper limit k(CrO,CrOH) <or= 10((-2+/-1)) M(-1) s(-1) for Cr(aq)O(2+)/Cr(aq)OH(2+) self-exchange. Even though superoxo complexes react very slowly in bimolecular self-reactions, extremely fast cross reactions with organic counterparts, i.e., acylperoxyl radicals, have been observed. Many of the intermediates generated by the interaction of O(2) with reduced metal complexes can also be accessed by alternative routes, both thermal and photochemical.
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Affiliation(s)
- Andreja Bakac
- Ames Laboratory and Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
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155
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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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156
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157
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Georgiev V, Noack H, Borowski T, Blomberg MRA, Siegbahn PEM. DFT Study on the Catalytic Reactivity of a Functional Model Complex for Intradiol-Cleaving Dioxygenases. J Phys Chem B 2010; 114:5878-85. [DOI: 10.1021/jp911217j] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Valentin Georgiev
- Department of Physics, Albanova, and Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91, Stockholm, Sweden
| | - Holger Noack
- Department of Physics, Albanova, and Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91, Stockholm, Sweden
| | - Tomasz Borowski
- Department of Physics, Albanova, and Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91, Stockholm, Sweden
| | - Margareta R. A. Blomberg
- Department of Physics, Albanova, and Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91, Stockholm, Sweden
| | - Per E. M. Siegbahn
- Department of Physics, Albanova, and Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91, Stockholm, Sweden
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158
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Jensen LMR, Sanishvili R, Davidson VL, Wilmot CM. In crystallo posttranslational modification within a MauG/pre-methylamine dehydrogenase complex. Science 2010; 327:1392-4. [PMID: 20223990 PMCID: PMC2878131 DOI: 10.1126/science.1182492] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
MauG is a diheme enzyme responsible for the posttranslational modification of two tryptophan residues to form the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase (MADH). MauG converts preMADH, containing monohydroxylated betaTrp57, to fully functional MADH by catalyzing the insertion of a second oxygen atom into the indole ring and covalently linking betaTrp57 to betaTrp108. We have solved the x-ray crystal structure of MauG complexed with preMADH to 2.1 angstroms. The c-type heme irons and the nascent TTQ site are separated by long distances over which electron transfer must occur to achieve catalysis. In addition, one of the hemes has an atypical His-Tyr axial ligation. The crystalline protein complex is catalytically competent; upon addition of hydrogen peroxide, MauG-dependent TTQ synthesis occurs.
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Affiliation(s)
- Lyndal M R Jensen
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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159
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Monooxygenases as biocatalysts: Classification, mechanistic aspects and biotechnological applications. J Biotechnol 2010; 146:9-24. [PMID: 20132846 DOI: 10.1016/j.jbiotec.2010.01.021] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 01/22/2010] [Accepted: 01/25/2010] [Indexed: 12/29/2022]
Abstract
Monooxygenases are enzymes that catalyze the insertion of a single oxygen atom from O(2) into an organic substrate. In order to carry out this type of reaction, these enzymes need to activate molecular oxygen to overcome its spin-forbidden reaction with the organic substrate. In most cases, monooxygenases utilize (in)organic cofactors to transfer electrons to molecular oxygen for its activation. Monooxygenases typically are highly chemo-, regio-, and/or enantioselective, making them attractive biocatalysts. In this review, an exclusive overview of known monooxygenases is presented, based on the type of cofactor that these enzymes require. This includes not only the cytochrome P450 and flavin-dependent monooxygenases, but also enzymes that utilize pterin, metal ions (copper or iron) or no cofactor at all. As most of these monooxygenases require nicotinamide coenzymes as electron donors, also an overview of current methods for coenzyme regeneration is given. This latter overview is of relevance for the biotechnological applications of these oxidative enzymes.
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160
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Peng RH, Xiong AS, Xue Y, Fu XY, Gao F, Zhao W, Tian YS, Yao QH. A profile of ring-hydroxylating oxygenases that degrade aromatic pollutants. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2010; 206:65-94. [PMID: 20652669 DOI: 10.1007/978-1-4419-6260-7_4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Numerous aromatic compounds are pollutants to which exposure exists or is possible, and are of concern because they are mutagenic, carcinogenic, or display other toxic characteristics. Depending on the types of dioxygenation reactions of which microorganisms are capable, they utilize ring-hydroxylating oxygenases (RHOs) to initiate the degradation and detoxification of such aromatic compound pollutants. Gene families encoding for RHOs appear to be most common in bacteria. Oxygenases are important in degrading both natural and synthetic aromatic compounds and are particularly important for their role in degrading toxic pollutants; for this reason, it is useful for environmental scientists and others to understand more of their characteristics and capabilities. It is the purpose of this review to address RHOs and to describe much of their known character, starting with a review as to how RHOs are classified. A comprehensive phylogenetic analysis has revealed that all RHOs are, in some measure, related, presumably by divergent evolution from a common ancestor, and this is reflected in how they are classified. After we describe RHO classification schemes, we address the relationship between RHO structure and function. Structural differences affect substrate specificity and product formation. In the alpha subunit of the known terminal oxygenase of RHOs, there is a catalytic domain with a mononuclear iron center that serves as a substrate-binding site and a Rieske domain that retains a [2Fe-2S] cluster that acts as an entity of electron transfer for the mononuclear iron center. Oxygen activation and substrate dihydroxylation occurring at the catalytic domain are dependent on the binding of substrate at the active site and the redox state of the Rieske center. The electron transfer from NADH to the catalytic pocket of RHO and catalyzing mechanism of RHOs is depicted in our review and is based on the results of recent studies. Electron transfer involving the RHO system typically involves four steps: NADH-ferredoxin reductase receives two electrons from NADH; ferredoxin binds with NADH-ferredoxin reductase and accepts electron from it; the reduced ferredoxin dissociates from NADH-ferredoxin reductase and shuttles the electron to the Rieske domain of the terminal oxygenase; the Rieske cluster donates electrons to O2 through the mononuclear iron. On the basis of crystal structure studies, it has been proposed that the broad specificity of the RHOs results from the large size and specific topology of its hydrophobic substrate-binding pocket. Several amino acids that determine the substrate specificity and enantioselectivity of RHOs have been identified through sequence comparison and site-directed mutagenesis at the active site. Exploiting the crystal structure data and the available active site information, engineered RHO enzymes have been and can be designed to improve their capacity to degrade environmental pollutants. Such attempts to enhance degradation capabilities of RHOs have been made. Dioxygenases have been modified to improve the degradation capacities toward PCBs, PAHs, dioxins, and some other aromatic hydrocarbons. We hope that the results of this review and future research on enhancing RHOs will promote their expanded usage and effectiveness for successfully degrading environmental aromatic pollutants.
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Affiliation(s)
- Ri-He Peng
- Shanghai Key Laboratory of Agricultural Genetics and Breeding, Agro-Biotechnology Research Institute, Shanghai Academy of Agricultural Sciences, 2901 Beidi Rd, Shanghai, People's Republic of China
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161
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Poliakov E, Gentleman S, Chander P, Cunningham FX, Grigorenko BL, Nemuhin AV, Redmond TM. Biochemical evidence for the tyrosine involvement in cationic intermediate stabilization in mouse beta-carotene 15, 15'-monooxygenase. BMC BIOCHEMISTRY 2009; 10:31. [PMID: 20003456 PMCID: PMC2801523 DOI: 10.1186/1471-2091-10-31] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Accepted: 12/14/2009] [Indexed: 11/10/2022]
Abstract
Background β-carotene 15,15'-monooxygenase (BCMO1) catalyzes the crucial first step in vitamin A biosynthesis in animals. We wished to explore the possibility that a carbocation intermediate is formed during the cleavage reaction of BCMO1, as is seen for many isoprenoid biosynthesis enzymes, and to determine which residues in the substrate binding cleft are necessary for catalytic and substrate binding activity. To test this hypothesis, we replaced substrate cleft aromatic and acidic residues by site-directed mutagenesis. Enzymatic activity was measured in vitro using His-tag purified proteins and in vivo in a β-carotene-accumulating E. coli system. Results Our assays show that mutation of either Y235 or Y326 to leucine (no cation-π stabilization) significantly impairs the catalytic activity of the enzyme. Moreover, mutation of Y326 to glutamine (predicted to destabilize a putative carbocation) almost eliminates activity (9.3% of wt activity). However, replacement of these same tyrosines with phenylalanine or tryptophan does not significantly impair activity, indicating that aromaticity at these residues is crucial. Mutations of two other aromatic residues in the binding cleft of BCMO1, F51 and W454, to either another aromatic residue or to leucine do not influence the catalytic activity of the enzyme. Our ab initio model of BCMO1 with β-carotene mounted supports a mechanism involving cation-π stabilization by Y235 and Y326. Conclusions Our data are consistent with the formation of a substrate carbocation intermediate and cation-π stabilization of this intermediate by two aromatic residues in the substrate-binding cleft of BCMO1.
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162
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Cho JH, Jung DK, Lee K, Rhee S. Crystal structure and functional analysis of the extradiol dioxygenase LapB from a long-chain alkylphenol degradation pathway in Pseudomonas. J Biol Chem 2009; 284:34321-30. [PMID: 19828456 PMCID: PMC2797200 DOI: 10.1074/jbc.m109.031054] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2009] [Revised: 10/09/2009] [Indexed: 11/06/2022] Open
Abstract
LapB is a non-heme Fe(II)-dependent 2,3-dioxygenase that catalyzes the second step of a long-chain alkylphenol (lap) degradation pathway in Pseudomonas sp. KL28 and belongs to the superfamily of type I extradiol dioxygenases. In this study, the crystal structures of substrate-free LapB and its complexes with a substrate or product were determined, along with a functional analysis of the active site residues. Structural features of the homotetramer are similar to those of other type I extradiol dioxygenases. In particular, the active site is located in the C-domain of each monomer, with a 2-His-1-carboxylate motif as the first coordination shell to iron ion. A comparison of three different structures in the catalytic cycle indicated catalysis-related local conformational changes in the active site. Specifically, the active site loop containing His-248 exhibits positional changes upon binding of the substrate and establishes a hydrogen-bonding network with Tyr-257, which is near the hydroxyl group of the substrate. Kinetic analysis of the mutant enzymes H248A, H248N, and Y257F showed that these three mutant enzymes are inactive, suggesting that this hydrogen-bonding network plays a crucial role in catalysis by deprotonating the incoming substrate and leaving it in a monoanionic state. Additional functional analysis of His-201, by using H201A and H201N mutants, near the dioxygen-binding site also supports its role as base and acid catalyst in the late stage of catalysis. We also noticed a disordered-to-ordered structural transition in the C-terminal region, resulting in the opening or closing of the active site. These results provide detailed insights into the structural and functional features of an extradiol dioxygenase that can accommodate a wide range of alkylcatechols.
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Affiliation(s)
- Jang-Hee Cho
- From the
Department of Agricultural Biotechnology
| | - Du-Kyo Jung
- From the
Department of Agricultural Biotechnology
| | - Kyoung Lee
- the
Department of Microbiology, Changwon National University, Kyongnam 641-773, Korea
| | - Sangkee Rhee
- From the
Department of Agricultural Biotechnology
- Center for Agricultural Biomaterials, and
- Center for Fugal Pathogenesis, Seoul National University, Seoul 151-921 and
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163
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Shin S, Lee S, Davidson VL. Suicide inactivation of MauG during reaction with O(2) or H(2)O(2) in the absence of its natural protein substrate. Biochemistry 2009; 48:10106-12. [PMID: 19788236 DOI: 10.1021/bi901284e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
MauG is a diheme protein that catalyzes the six-electron oxidation of a biosynthetic precursor protein of methylamine dehydrogenase (PreMADH) with partially synthesized tryptophan tryptophylquinone (TTQ) to yield the mature protein with the functional protein-derived TTQ cofactor. The biosynthetic reaction proceeds via a relatively stable high valent bis-Fe(IV) intermediate. Oxidizing equivalents ([O]) for this reaction may be provided by either O(2) plus electrons from an external donor or H(2)O(2). The presence or absence of PreMADH has no influence on the reactivity of MauG with [O]; however, it is demonstrated that MauG is inactivated when supplied with [O] in the absence of PreMADH. The mechanism of inactivation appears to differ depending on the source of [O]. Repeated reaction of diferrous MauG with O(2) leads to loss of activity but not inactivation of heme, as judged by absorption spectroscopy and pyridine hemochrome assay. Repeated reaction of diferric MauG with H(2)O(2) leads to loss of activity and inactivation of heme, as well as some covalent cross-linking of MauG molecules. None of these deleterious effects with either source of [O] are observed when PreMADH is present to react with MauG. The radical scavenger hydroxyurea and small molecule mimics of the monohydroxylated Trp residue of PreMADH also reacted with bis-Fe(IV) MauG and afforded protection against inactivation. These results demonstrate that while O(2) and H(2)O(2) readily react with MauG in the absence of PreMADH, the presence of this substrate is necessary to prevent suicide inactivation of MauG after formation of the bis-Fe(IV) intermediate.
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Affiliation(s)
- Sooim Shin
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi 39216, USA
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164
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Determination of the active site of Sphingobium chlorophenolicum 2,6-dichlorohydroquinone dioxygenase (PcpA). J Biol Inorg Chem 2009; 15:291-301. [DOI: 10.1007/s00775-009-0602-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2009] [Accepted: 10/09/2009] [Indexed: 10/20/2022]
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165
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Finding molecular dioxygen tunnels in homoprotocatechuate 2,3-dioxygenase: implications for different reactivity of identical subunits. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:327-36. [PMID: 19826803 DOI: 10.1007/s00249-009-0551-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2009] [Revised: 09/09/2009] [Accepted: 09/24/2009] [Indexed: 10/20/2022]
Abstract
Extradiol dioxygenases facilitate microbial aerobic degradation of catechol and its derivatives by activating molecular dioxygen and incorporating both oxygen atoms into their substrates. Experimental and theoretical studies have focused on the mechanism of the reaction at the active site. However, whether the catalytic rate is limited by O(2) access to the active site has not yet been explored. Here, we choose a recently solved X-ray structure of homoprotocatechuate 2,3-dioxygenase as a typical example to determine potential pathways for O(2) migration from the solvent into the enzyme center. On the basis of the trajectories of two 10-ns molecular dynamics simulations, implicit ligand sampling was used to calculate the 3D free energy map for O(2) inside the protein. The energetically optimal routes for O(2) diffusion were identified for each subunit of the homotetrameric protein structure. The O(2) tunnels formed because of thermal fluctuations were also characterized by connecting elongated cavities inside the protein. By superimposing the favorable O(2) tunnels on to the free energy map, both energetically and geometrically preferred O(2) pathways were determined, as also were the amino acids that may be critical for O(2) passage along these paths. Our results demonstrate that identical subunits possess quite distinct O(2) tunnels. The order of O(2) affinity of these tunnels is generally consistent with the order of the catalytic rate of each subunit. As a consequence, the probability of finding the reaction product is highest in the subunit containing the highest O(2) affinity pathway.
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166
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Xu L, Liu X, Zhao W, Wang X. Locally Enhanced Sampling Study of Dioxygen Diffusion Pathways in Homoprotocatechuate 2,3-Dioxygenase. J Phys Chem B 2009; 113:13596-603. [DOI: 10.1021/jp902597t] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Liang Xu
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Xin Liu
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Weijie Zhao
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
| | - Xicheng Wang
- Department of Engineering Mechanics, State Key Laboratory of Structural Analyses for Industrial Equipment, and Department of Chemistry, Dalian University of Technology, Dalian 116023, China, and School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116012, China
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167
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Charkin OP, Makarov AV, Klimenko NM. Theoretical study of the model reaction of oxidation of methane to methyl alcohol by Fe(P)O(NH2) and related oxoferryl porphyrin complexes (P = C20H12N4). RUSS J INORG CHEM+ 2009. [DOI: 10.1134/s0036023609090149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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168
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Chaiyen P. Flavoenzymes catalyzing oxidative aromatic ring-cleavage reactions. Arch Biochem Biophys 2009; 493:62-70. [PMID: 19728986 DOI: 10.1016/j.abb.2009.08.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2009] [Revised: 08/24/2009] [Accepted: 08/26/2009] [Indexed: 11/25/2022]
Abstract
2-Methyl-3-hydroxypyridine-5-carboxylic acid (MHPC) oxygenase (MHPCO) and 5-pyridoxic acid oxygenase are flavoenzymes catalyzing an aromatic hydroxylation and a ring-cleavage reaction. Both enzymes are involved in biodegradation of vitamin B6 in bacteria. Oxygen-tracer experiments have shown that the enzymes are monooxygnases since only one atom of molecular oxygen is incorporated into the products. Kinetics of MHPCO has shown that the enzyme is similar to single-component flavoprotein hydroxylases in that the binding of MHPC is required prior to the flavin reduction by NADH, and C4a-hydroperoxy-FAD and C4a-hydroxy-FAD are found as intermediates. Investigation on the protonation status of the substrate upon binding to the enzyme has shown that only the tri-ionic form of MHPC is bound at the MHPCO active site. Using a series of FAD analogues with substituents at the 8-position of the isoalloxazine ring, the oxygenation of MHPC by the C4a-hydroperoxy-FAD was shown to occur via an electrophilic aromatic substitution mechanism. Recently, the X-ray structures of MHPCO and a complex of MHPC-MHPCO at 2.1A have been reported and show the presence of nine water molecules in the enzyme active site. Based on structural data, a few residues, Tyr82, Tyr223, Arg181, were suggested to be important for catalysis of MHPCO.
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Affiliation(s)
- Pimchai Chaiyen
- Department of Biochemistry and Center of Excellence in Protein Structure and Function, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok, 10400, Thailand.
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169
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170
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Crystal structure of dicamba monooxygenase: a Rieske nonheme oxygenase that catalyzes oxidative demethylation. J Mol Biol 2009; 392:498-510. [PMID: 19616011 DOI: 10.1016/j.jmb.2009.07.021] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 07/04/2009] [Accepted: 07/09/2009] [Indexed: 11/20/2022]
Abstract
Dicamba (3,6-dichloro-2-methoxybenzoic acid) is a widely used herbicide that is efficiently degraded by soil microbes. These microbes use a novel Rieske nonheme oxygenase, dicamba monooxygenase (DMO), to catalyze the oxidative demethylation of dicamba to 3,6-dichlorosalicylic acid (DCSA) and formaldehyde. We have determined the crystal structures of DMO in the free state, bound to its substrate dicamba, and bound to the product DCSA at 2.10-1.75 A resolution. The structures show that the DMO active site uses a combination of extensive hydrogen bonding and steric interactions to correctly orient chlorinated, ortho-substituted benzoic-acid-like substrates for catalysis. Unlike other Rieske aromatic oxygenases, DMO oxygenates the exocyclic methyl group, rather than the aromatic ring, of its substrate. This first crystal structure of a Rieske demethylase shows that the Rieske oxygenase structural scaffold can be co-opted to perform varied types of reactions on xenobiotic substrates.
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Abstracts of the 14th International Conference on Biological Inorganic Chemistry. July 25-30, 2009. Nagoya, Japan. J Biol Inorg Chem 2009; 14 Suppl 1:5-7. [PMID: 19578879 DOI: 10.1007/s00775-009-0523-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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172
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173
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Yam KC, D'Angelo I, Kalscheuer R, Zhu H, Wang JX, Snieckus V, Ly LH, Converse PJ, Jacobs WR, Strynadka N, Eltis LD. Studies of a ring-cleaving dioxygenase illuminate the role of cholesterol metabolism in the pathogenesis of Mycobacterium tuberculosis. PLoS Pathog 2009; 5:e1000344. [PMID: 19300498 PMCID: PMC2652662 DOI: 10.1371/journal.ppat.1000344] [Citation(s) in RCA: 178] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2008] [Accepted: 02/20/2009] [Indexed: 01/07/2023] Open
Abstract
Mycobacterium tuberculosis, the etiological agent of TB, possesses a cholesterol catabolic pathway implicated in pathogenesis. This pathway includes an iron-dependent extradiol dioxygenase, HsaC, that cleaves catechols. Immuno-compromised mice infected with a DeltahsaC mutant of M. tuberculosis H37Rv survived 50% longer than mice infected with the wild-type strain. In guinea pigs, the mutant disseminated more slowly to the spleen, persisted less successfully in the lung, and caused little pathology. These data establish that, while cholesterol metabolism by M. tuberculosis appears to be most important during the chronic stage of infection, it begins much earlier and may contribute to the pathogen's dissemination within the host. Purified HsaC efficiently cleaved the catecholic cholesterol metabolite, DHSA (3,4-dihydroxy-9,10-seconandrost-1,3,5(10)-triene-9,17-dione; k(cat)/K(m) = 14.4+/-0.5 microM(-1) s(-1)), and was inactivated by a halogenated substrate analogue (partition coefficient<50). Remarkably, cholesterol caused loss of viability in the DeltahsaC mutant, consistent with catechol toxicity. Structures of HsaC:DHSA binary complexes at 2.1 A revealed two catechol-binding modes: bidentate binding to the active site iron, as has been reported in similar enzymes, and, unexpectedly, monodentate binding. The position of the bicyclo-alkanone moiety of DHSA was very similar in the two binding modes, suggesting that this interaction is a determinant in the initial substrate-binding event. These data provide insights into the binding of catechols by extradiol dioxygenases and facilitate inhibitor design.
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Affiliation(s)
- Katherine C. Yam
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Igor D'Angelo
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rainer Kalscheuer
- Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Haizhong Zhu
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Jian-Xin Wang
- Department of Chemistry, Queen's University, Kingston, Ontario, Canada
| | - Victor Snieckus
- Department of Chemistry, Queen's University, Kingston, Ontario, Canada
| | - Lan H. Ly
- Department of Microbial and Molecular Pathogenesis, Texas A&M University Health Science Center, College Station, Texas, United States of America
| | - Paul J. Converse
- Center for Tuberculosis Research, Department of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - William R. Jacobs
- Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Natalie Strynadka
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Lindsay D. Eltis
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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174
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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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175
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İşci Ü, Afanasiev P, Millet JMM, Kudrik EV, Ahsen V, Sorokin AB. Preparation and characterization of μ-nitrido diiron phthalocyanines with electron-withdrawing substituents: application for catalytic aromatic oxidation. Dalton Trans 2009:7410-20. [DOI: 10.1039/b902592h] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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176
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Jo Y, Annaraj J, Seo MS, Lee YM, Kim SY, Cho J, Nam W. Reactivity of a cobalt(III)-peroxo complex in oxidative nucleophilic reactions. J Inorg Biochem 2008; 102:2155-9. [DOI: 10.1016/j.jinorgbio.2008.08.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 07/29/2008] [Accepted: 08/13/2008] [Indexed: 10/21/2022]
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177
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Lipscomb JD. Mechanism of extradiol aromatic ring-cleaving dioxygenases. Curr Opin Struct Biol 2008; 18:644-9. [PMID: 19007887 DOI: 10.1016/j.sbi.2008.11.001] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Revised: 08/14/2008] [Accepted: 11/04/2008] [Indexed: 10/21/2022]
Abstract
The extradiol aromatic ring-cleaving dioxygenases activate molecular oxygen by binding both O(2) and the catecholic substrate to a reduced active site metal, generally Fe(II). Progress has been made in understanding the mechanism of this reaction through the combined use of kinetic, computational, biomimetic, structural, and diagnostic chemical approaches. It appears that O(2) is activated by accepting an electron transferred from the substrate through the metal, thereby simultaneously activating oxygen and substrate for reaction with each other.
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Affiliation(s)
- John D Lipscomb
- Department of Biochemistry, Molecular Biology, and Biophysics, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN 55455, USA.
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178
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Gunderson WA, Zatsman AI, Emerson JP, Farquhar ER, Que L, Lipscomb JD, Hendrich MP. Electron paramagnetic resonance detection of intermediates in the enzymatic cycle of an extradiol dioxygenase. J Am Chem Soc 2008; 130:14465-7. [PMID: 18839948 DOI: 10.1021/ja8052255] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Extradiol catecholic dioxygenases catalyze the cleavage of the aromatic ring of the substrate with incorporation of both oxygen atoms from O2. These enzymes are important in nature for the recovery of large amounts of carbon from aromatic compounds. The catalytic site contains either Fe or Mn coordinated by a facial triad of two His and one Glu or Asp residues. Previous studies have shown that Fe(II) and Mn(II) can be interchanged in enzymes from different organisms to catalyze similar substrate reactions. In combination, quantitative electron paramagnetic resonance spectroscopy and rapid freeze-quench experiments allow us to follow the concentrations of four different Mn species, including key metal intermediates in the catalytic cycle, as the enzyme turns over its natural substrate. Two intermediates are observed: a Mn(III)-radical species which is either Mn-superoxide or Mn-substrate radical, and a unique Mn(II) species which is involved in the rate-limiting step of the cycle and may be Mn-alkylperoxo.
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Affiliation(s)
- William A Gunderson
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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179
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Namuswe F, Kasper GD, Sarjeant AAN, Hayashi T, Krest CM, Green MT, Moënne-Loccoz P, Goldberg DP. Rational tuning of the thiolate donor in model complexes of superoxide reductase: direct evidence for a trans influence in Fe(III)-OOR complexes. J Am Chem Soc 2008; 130:14189-200. [PMID: 18837497 DOI: 10.1021/ja8031828] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron peroxide species have been identified as important intermediates in a number of nonheme iron as well as heme-containing enzymes, yet there are only a few examples of such species either synthetic or biological that have been well characterized. We describe the synthesis and structural characterization of a new series of five-coordinate (N4S(thiolate))Fe(II) complexes that react with tert-butyl hydroperoxide ((t)BuOOH) or cumenyl hydroperoxide (CmOOH) to give metastable alkylperoxo-iron(III) species (N4S(thiolate)Fe(III)-OOR) at low temperature. These complexes were designed specifically to mimic the nonheme iron active site of superoxide reductase, which contains a five-coordinate iron(II) center bound by one Cys and four His residues in the active form of the protein. The structures of the Fe(II) complexes are analyzed by X-ray crystallography, and their electrochemical properties are assessed by cyclic voltammetry. For the Fe(III)-OOR species, low-temperature UV-vis spectra reveal intense peaks between 500-550 nm that are typical of peroxide to iron(III) ligand-to-metal charge-transfer (LMCT) transitions, and EPR spectroscopy shows that these alkylperoxo species are all low-spin iron(III) complexes. Identification of the vibrational modes of the Fe(III)-OOR unit comes from resonance Raman (RR) spectroscopy, which shows nu(Fe-O) modes between 600-635 cm(-1) and nu(O-O) bands near 800 cm(-1). These Fe-O stretching frequencies are significantly lower than those found in other low-spin Fe(III)-OOR complexes. Trends in the data conclusively show that this weakening of the Fe-O bond arises from a trans influence of the thiolate donor, and density functional theory (DFT) calculations support these findings. These results suggest a role for the cysteine ligand in SOR, and are discussed in light of the recent assessments of the function of the cysteine ligand in this enzyme.
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Affiliation(s)
- Frances Namuswe
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
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180
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Kovaleva EG, Lipscomb JD. Intermediate in the O-O bond cleavage reaction of an extradiol dioxygenase. Biochemistry 2008; 47:11168-70. [PMID: 18826259 DOI: 10.1021/bi801459q] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The reactive oxy intermediate of the catalytic cycle of extradiol aromatic ring-cleaving dioxygenases is formed by binding the catecholic substrate and O2 in adjacent ligand positions of the active site metal [usually Fe(II)]. This intermediate and the following Fe(II)-alkylperoxo intermediate resulting from oxygen attack on the substrate have been previously characterized in a crystal of homoprotocatechuate 2,3-dioxygenase (HPCD). Here a subsequent intermediate in which the O-O bond is broken to yield a gem diol species is structurally characterized. This new intermediate is stabilized in the crystal by using the alternative substrate, 4-sulfonylcatechol, and the Glu323Leu variant of HPCD, which alters the crystal packing.
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Affiliation(s)
- Elena G Kovaleva
- Department of Biochemistry, Molecular Biology, and Biophysics and Center for Metals in Biocatalysis, 321 Church Street SE, University of Minnesota, Minneapolis, Minnesota 55455, USA
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181
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Zhao Y, Zhu S, Shao M, Jia T, Li M, Lu W, He W. Synthesis, crystal structures and selective oxygenation of dinuclear copper(II) complexes of N,N,N′,N′-xylylenediamine tetraacetate. INORG CHEM COMMUN 2008. [DOI: 10.1016/j.inoche.2008.04.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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182
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Andreini C, Bertini I, Cavallaro G, Holliday GL, Thornton JM. Metal ions in biological catalysis: from enzyme databases to general principles. J Biol Inorg Chem 2008; 13:1205-18. [PMID: 18604568 DOI: 10.1007/s00775-008-0404-5] [Citation(s) in RCA: 734] [Impact Index Per Article: 45.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2008] [Accepted: 06/25/2008] [Indexed: 12/01/2022]
Abstract
We analysed the roles and distribution of metal ions in enzymatic catalysis using available public databases and our new resource Metal-MACiE (http://www.ebi.ac.uk/thornton-srv/databases/Metal_MACiE/home.html). In Metal-MACiE, a database of metal-based reaction mechanisms, 116 entries covering 21% of the metal-dependent enzymes and 70% of the types of enzyme-catalysed chemical transformations are annotated according to metal function. We used Metal-MACiE to assess the functions performed by metals in biological catalysis and the relative frequencies of different metals in different roles, which can be related to their individual chemical properties and availability in the environment. The overall picture emerging from the overview of Metal-MACiE is that redox-inert metal ions are used in enzymes to stabilize negative charges and to activate substrates by virtue of their Lewis acid properties, whereas redox-active metal ions can be used both as Lewis acids and as redox centres. Magnesium and zinc are by far the most common ions of the first type, while calcium is relatively less used. Magnesium, however, is most often bound to phosphate groups of substrates and interacts with the enzyme only transiently, whereas the other metals are stably bound to the enzyme. The most common metal of the second type is iron, which is prevalent in the catalysis of redox reactions, followed by manganese, cobalt, molybdenum, copper and nickel. The control of the reactivity of redox-active metal ions may involve their association with organic cofactors to form stable units. This occurs sometimes for iron and nickel, and quite often for cobalt and molybdenum.
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Affiliation(s)
- Claudia Andreini
- Magnetic Resonance Center (CERM), University of Florence, Via L. Sacconi 6, 50019, Sesto Fiorentino, Italy
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183
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A catalytic di-heme bis-Fe(IV) intermediate, alternative to an Fe(IV)=O porphyrin radical. Proc Natl Acad Sci U S A 2008; 105:8597-600. [PMID: 18562294 DOI: 10.1073/pnas.0801643105] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
High-valent iron species are powerful oxidizing agents in chemical and biological catalysis. The best characterized form of an Fe(V) equivalent described in biological systems is the combination of a b-type heme with Fe(IV)=O and a porphyrin or amino acid cation radical (termed Compound I). This work describes an alternative natural mechanism to store two oxidizing equivalents above the ferric state for biological oxidation reactions. MauG is an enzyme that utilizes two covalently bound c-type hemes to catalyze the biosynthesis of the protein-derived cofactor tryptophan tryptophylquinone. Its natural substrate is a monohydroxylated tryptophan residue present in a 119-kDa precursor protein. An EPR-silent di-heme reaction intermediate of MauG was trapped. Mössbauer spectroscopy revealed the presence of two distinct Fe(IV) species. One is consistent with an Fe(IV)=O (ferryl) species (delta = 0.06 mm/s, DeltaE(Q) = 1.70 mm/s). The other is assigned to an Fe(IV) heme species with two axial ligands from protein (delta = 0.17 mm/s, DeltaE(Q) = 2.54 mm/s), which has never before been described in nature. This bis-Fe(IV) intermediate is remarkably stable but readily reacts with its native substrate. These findings broaden our views of how proteins can stabilize a highly reactive oxidizing species and the scope of enzyme-catalyzed posttranslational modifications.
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184
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185
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A comparison of the reaction mechanisms of iron- and manganese-containing 2,3-HPCD: an important spin transition for manganese. J Biol Inorg Chem 2008; 13:929-40. [DOI: 10.1007/s00775-008-0380-9] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Accepted: 04/15/2008] [Indexed: 10/22/2022]
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186
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Pérez LM, Webster CE, Low AA, Hall MB. Theoretical study of the biologically important dioxo diiron diamond core structures. Theor Chem Acc 2008. [DOI: 10.1007/s00214-008-0438-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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187
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Kovaleva EG, Lipscomb JD. Versatility of biological non-heme Fe(II) centers in oxygen activation reactions. Nat Chem Biol 2008; 4:186-93. [PMID: 18277980 PMCID: PMC2720164 DOI: 10.1038/nchembio.71] [Citation(s) in RCA: 492] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Oxidase and oxygenase enzymes allow the use of relatively unreactive O2 in biochemical reactions. Many of the mechanistic strategies used in nature for this key reaction are represented within the 2-histidine-1-carboxylate facial triad family of non-heme Fe(II)-containing enzymes. The open face of the metal coordination sphere opposite the three endogenous ligands participates directly in the reaction chemistry. Here, data from several studies are presented showing that reductive O2 activation within this family is initiated by substrate (and in some cases cosubstrate or cofactor) binding, which then allows coordination of O2 to the metal. From this starting point, the O2 activation process and the reactions with substrates diverge broadly. The reactive species formed in these reactions have been proposed to encompass four oxidation states of iron and all forms of reduced O2 as well as several of the reactive oxygen species that derive from O-O bond cleavage.
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Affiliation(s)
- Elena G Kovaleva
- Elena G. Kovaleva and John D. Lipscomb are in the Department of Biochemistry, Molecular Biology and Biophysics and the Center for Metals in Biocatalysis, University of Minnesota, 6-155 Jackson Hall, Minneapolis, Minnesota, 55455 USA
| | - John D Lipscomb
- Elena G. Kovaleva and John D. Lipscomb are in the Department of Biochemistry, Molecular Biology and Biophysics and the Center for Metals in Biocatalysis, University of Minnesota, 6-155 Jackson Hall, Minneapolis, Minnesota, 55455 USA
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188
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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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189
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Sorokin AB, Kudrik EV, Bouchu D. Bio-inspired oxidation of methane in water catalyzed by N-bridged diiron phthalocyanine complex. Chem Commun (Camb) 2008:2562-4. [DOI: 10.1039/b804405h] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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190
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191
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Synthetic iron-oxo "diamond core" mimics structure of key intermediate in methane monooxygenase catalytic cycle. Proc Natl Acad Sci U S A 2007; 104:20641-2. [PMID: 18093936 DOI: 10.1073/pnas.0710734105] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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192
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Szajna-Fuller E, Bakac A. Thermodynamics of oxygen activation by macrocyclic complexes of rhodium. Inorg Chem 2007; 46:10907-12. [PMID: 17985876 DOI: 10.1021/ic7015337] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The oxidation of ABTS2- [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate)] with a superoxorhodium(III) complex, L2(H2O)RhOO2+ (L2 = meso-hexamethylcyclam) is characterized by an acid-dependent equilibrium constant, log(Ke/[H+]) = 4.91 +/- 0.10 in the pH range of 4.89-6.49. This equilibrium constant was used to calculate the reduction potential for the L2(H2O)RhOO2+/L2(H2O)RhOOH2+ couple, E0 = 0.97 V vs NHE. The pH dependence of the kinetics of the L2(H2O)RhOOH2+/I- reaction yielded the acid dissociation constant for the coordinated water in L2(H2O)RhOOH2+, pKa = 6.9. Spectrophotometric pH titrations provided pKa = 6.6 for the superoxo complex, L2(H2O)RhOO2+. The combination of the two pKa values with the reduction potential measured in acidic solutions yielded the reduction potential E0 = 0.95 V for the L2(HO)RhOO+/L2(HO)RhOOH+ couple. Thermochemical calculations yielded the bond-dissociation free energy of the L2(H2O)RhOO-H2+ bond as 315 kJ/mol at 298 K.
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193
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Reisner E, Abikoff TC, Lippard SJ. Influence of Steric Hindrance on the Core Geometry and Sulfoxidation Chemistry of Carboxylate-Rich Diiron(II) Complexes. Inorg Chem 2007; 46:10229-40. [DOI: 10.1021/ic7014176] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Erwin Reisner
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Tanya C. Abikoff
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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194
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Gong Y, Zhou M. Formation and Characterization of the Oxygen-Rich Hafnium Dioxygen Complexes: OHf(η2-O2)(η2-O3), Hf(η2-O2)3, and Hf(η2-O2)4. J Phys Chem A 2007; 111:8973-9. [PMID: 17718464 DOI: 10.1021/jp074531m] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hafnium atom oxidation by dioxygen molecules has been investigated using matrix isolation infrared absorption spectroscopy. The ground-state hafnium atom inserts into dioxygen to form primarily the previously characterized HfO(2) molecule in solid argon. Annealing allows the dioxygen molecules to diffuse and react with HfO(2) to form OHf(eta(2)-O(2))(eta(2)-O(3)), which is characterized as a side-on bonded oxo-superoxo hafnium ozonide complex. Under visible light (532 nm) irradiation, the OHf(eta(2)-O(2))(eta(2)-O(3)) complex either photochemically rearranges to a more stable Hf(eta(2)-O(2))(3) isomer, a side-on bonded di-superoxo hafnium peroxide complex, or reacts with dioxygen to form an unprecedented homoleptic tetra-superoxo hafnium complex: Hf(eta(2)-O(2))(4). The Hf(eta(2)-O(2))(4) complex is determined to possess a D(2d) geometry with a tetrahedral arrangement of four side-on bonded O(2) ligands around the hafnium atom, which thus presents an 8-fold coordination. These oxygen-rich complexes are photoreversible; that is, formation of Hf(eta(2)-O(2))(3) and Hf(eta(2)-O(2))(4) is accompanied by demise of OHf(eta(2)-O(2))(eta(2)-O(3)) under visible (532 nm) light irradiation and vice versa with UV (266 nm) light irradiation.
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Affiliation(s)
- Yu Gong
- Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Advanced Materials Laboratory, Fudan University, Shanghai 200433, People's Republic of China
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