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Volmer JG, Soo RM, Evans PN, Hoedt EC, Astorga Alsina AL, Woodcroft BJ, Tyson GW, Hugenholtz P, Morrison M. Isolation and characterisation of novel Methanocorpusculum species indicates the genus is ancestrally host-associated. BMC Biol 2023; 21:59. [PMID: 36949471 PMCID: PMC10035134 DOI: 10.1186/s12915-023-01524-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/20/2023] [Indexed: 03/24/2023] Open
Abstract
BACKGROUND With an increasing interest in the manipulation of methane produced from livestock cultivation, the microbiome of Australian marsupials provides a unique ecological and evolutionary comparison with 'low-methane' emitters. Previously, marsupial species were shown to be enriched for novel lineages of Methanocorpusculum, as well as Methanobrevibacter, Methanosphaera, and Methanomassiliicoccales. Despite sporadic reports of Methanocorpusculum from stool samples of various animal species, there remains little information on the impacts of these methanogens on their hosts. RESULTS Here, we characterise novel host-associated species of Methanocorpusculum, to explore unique host-specific genetic factors and their associated metabolic potential. We performed comparative analyses on 176 Methanocorpusculum genomes comprising 130 metagenome-assembled genomes (MAGs) recovered from 20 public animal metagenome datasets and 35 other publicly available Methanocorpusculum MAGs and isolate genomes of host-associated and environmental origin. Nine MAGs were also produced from faecal metagenomes of the common wombat (Vombatus ursinus) and mahogany glider (Petaurus gracilis), along with the cultivation of one axenic isolate from each respective animal; M. vombati (sp. nov.) and M. petauri (sp. nov.). CONCLUSIONS Through our analyses, we substantially expand the available genetic information for this genus by describing the phenotypic and genetic characteristics of 23 host-associated species of Methanocorpusculum. These lineages display differential enrichment of genes associated with methanogenesis, amino acid biosynthesis, transport system proteins, phosphonate metabolism, and carbohydrate-active enzymes. These results provide insights into the differential genetic and functional adaptations of these novel host-associated species of Methanocorpusculum and suggest that this genus is ancestrally host-associated.
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Affiliation(s)
- James G Volmer
- Faculty of Medicine, University of Queensland Frazer Institute, Translational Research Institute, Woolloongabba, 4102, Australia
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, 4102, Australia
| | - Rochelle M Soo
- School of Chemistry and Molecular Biosciences and Australian Centre for Ecogenomics, University of Queensland, Saint Lucia, 4072, Australia
| | - Paul N Evans
- School of Chemistry and Molecular Biosciences and Australian Centre for Ecogenomics, University of Queensland, Saint Lucia, 4072, Australia
| | - Emily C Hoedt
- Faculty of Medicine, University of Queensland Frazer Institute, Translational Research Institute, Woolloongabba, 4102, Australia
- Current Address: NHMRC Centre of Research Excellence (CRE) in Digestive Health, Hunter Medical Research Institute (HMRI), Newcastle, NSW, Australia
| | - Ana L Astorga Alsina
- Faculty of Medicine, University of Queensland Frazer Institute, Translational Research Institute, Woolloongabba, 4102, Australia
| | - Benjamin J Woodcroft
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, 4102, Australia
| | - Gene W Tyson
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, 4102, Australia
| | - Philip Hugenholtz
- School of Chemistry and Molecular Biosciences and Australian Centre for Ecogenomics, University of Queensland, Saint Lucia, 4072, Australia
| | - Mark Morrison
- Faculty of Medicine, University of Queensland Frazer Institute, Translational Research Institute, Woolloongabba, 4102, Australia.
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QM/MM study of the [4Fe-4S]-dependent (R)-2-hydroxyisocaproyl-CoA dehydratase: Dehydration via a redox pathway with an α-carbonyl radical intermediate. J Catal 2023. [DOI: 10.1016/j.jcat.2023.01.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
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Metabolic activity analyses demonstrate that Lokiarchaeon exhibits homoacetogenesis in sulfidic marine sediments. Nat Microbiol 2019; 5:248-255. [PMID: 31873205 DOI: 10.1038/s41564-019-0630-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/04/2019] [Indexed: 01/09/2023]
Abstract
The genomes of the Asgard superphylum of Archaea hold clues pertaining to the nature of the host cell that acquired the mitochondrion at the origin of eukaryotes1-4. Representatives of the Asgard candidate phylum Candidatus Lokiarchaeota (Lokiarchaeon) have the capacity for acetogenesis and fermentation5-7, but how their metabolic activity responds to environmental conditions is poorly understood. Here, we show that in anoxic Namibian shelf sediments, Lokiarchaeon gene expression levels are higher than those of bacterial phyla and increase with depth below the seafloor. Lokiarchaeon gene expression was significantly different across a hypoxic-sulfidic redox gradient, whereby genes involved in growth, fermentation and H2-dependent carbon fixation had the highest expression under the most reducing (sulfidic) conditions. Quantitative stable isotope probing revealed that anaerobic utilization of CO2 and diatomaceous extracellular polymeric substances by Lokiarchaeon was higher than the bacterial average, consistent with higher expression of Lokiarchaeon genes, including those involved in transport and fermentation of sugars and amino acids. The quantitative stable isotope probing and gene expression data demonstrate homoacetogenic activity of Candidatus Lokiarchaeota, whereby fermentative H2 production from organic substrates is coupled with the Wood-Ljungdahl carbon fixation pathway8. The high energetic efficiency provided by homoacetogenesis8 helps to explain the elevated metabolic activity of Lokiarchaeon in this anoxic, energy-limited setting.
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Microbial Organic Matter Degradation Potential in Baltic Sea Sediments Is Influenced by Depositional Conditions and In Situ Geochemistry. Appl Environ Microbiol 2019; 85:AEM.02164-18. [PMID: 30504213 PMCID: PMC6365825 DOI: 10.1128/aem.02164-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 11/17/2018] [Indexed: 11/23/2022] Open
Abstract
Sediments sequester organic matter over geologic time scales and impact global climate regulation. Microbial communities in marine sediments drive organic matter degradation, but the factors controlling their assemblages and activities, which in turn impact their role in organic matter degradation, are not well understood. Hence, determining the role of microbial communities in carbon cycling in various sediment types is necessary for predicting future sediment carbon cycling. We examined microbial communities in Baltic Sea sediments, which were deposited across various climatic and geographical regimes to determine the relationship between microbial potential for breakdown of organic matter and abiotic factors, including geochemistry and sediment lithology. The findings from this study will contribute to our understanding of carbon cycling in the deep biosphere and how microbial communities live in deeply buried environments. Globally, marine sediments are a vast repository of organic matter, which is degraded through various microbial pathways, including polymer hydrolysis and monomer fermentation. The sources, abundances, and quality (i.e., labile or recalcitrant) of the organic matter and the composition of the microbial assemblages vary between sediments. Here, we examine new and previously published sediment metagenomes from the Baltic Sea and the nearby Kattegat region to determine connections between geochemistry and the community potential to degrade organic carbon. Diverse organic matter hydrolysis encoding genes were present in sediments between 0.25 and 67 meters below seafloor and were in higher relative abundances in those sediments that contained more organic matter. New analysis of previously published metatranscriptomes demonstrated that many of these genes were transcribed in two organic-rich Holocene sediments. Some of the variation in deduced pathways in the metagenomes correlated with carbon content and depositional conditions. Fermentation-related genes were found in all samples and encoded multiple fermentation pathways. Notably, genes involved in alcohol metabolism were amongst the most abundant of these genes, indicating that this is an important but underappreciated aspect of sediment carbon cycling. This study is a step towards a more complete understanding of microbial food webs and the impacts of depositional facies on present sedimentary microbial communities. IMPORTANCE Sediments sequester organic matter over geologic time scales and impact global climate regulation. Microbial communities in marine sediments drive organic matter degradation, but the factors controlling their assemblages and activities, which in turn impact their role in organic matter degradation, are not well understood. Hence, determining the role of microbial communities in carbon cycling in various sediment types is necessary for predicting future sediment carbon cycling. We examined microbial communities in Baltic Sea sediments, which were deposited across various climatic and geographical regimes to determine the relationship between microbial potential for breakdown of organic matter and abiotic factors, including geochemistry and sediment lithology. The findings from this study will contribute to our understanding of carbon cycling in the deep biosphere and how microbial communities live in deeply buried environments.
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Ferreira S, Pereira R, Liu F, Vilaça P, Rocha I. Discovery and implementation of a novel pathway for n-butanol production via 2-oxoglutarate. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:230. [PMID: 31583016 PMCID: PMC6767645 DOI: 10.1186/s13068-019-1565-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 09/07/2019] [Indexed: 05/12/2023]
Abstract
BACKGROUND One of the European Union directives indicates that 10% of all fuels must be bio-synthesized by 2020. In this regard, biobutanol-natively produced by clostridial strains-poses as a promising alternative biofuel. One possible approach to overcome the difficulties of the industrial exploration of the native producers is the expression of more suitable pathways in robust microorganisms such as Escherichia coli. The enumeration of novel pathways is a powerful tool, allowing to identify non-obvious combinations of enzymes to produce a target compound. RESULTS This work describes the in silico driven design of E. coli strains able to produce butanol via 2-oxoglutarate by a novel pathway. This butanol pathway was generated by a hypergraph algorithm and selected from an initial set of 105,954 different routes by successively applying different filters, such as stoichiometric feasibility, size and novelty. The implementation of this pathway involved seven catalytic steps and required the insertion of nine heterologous genes from various sources in E. coli distributed in three plasmids. Expressing butanol genes in E. coli K12 and cultivation in High-Density Medium formulation seem to favor butanol accumulation via the 2-oxoglutarate pathway. The maximum butanol titer obtained was 85 ± 1 mg L-1 by cultivating the cells in bioreactors. CONCLUSIONS In this work, we were able to successfully translate the computational analysis into in vivo applications, designing novel strains of E. coli able to produce n-butanol via an innovative pathway. Our results demonstrate that enumeration algorithms can broad the spectrum of butanol producing pathways. This validation encourages further research to other target compounds.
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Affiliation(s)
- Sofia Ferreira
- CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Rui Pereira
- SilicoLife Lda, Rua do Canastreiro 15, 4715-387 Braga, Portugal
- Present Address: Department of Biology and Biological Engineering, Chalmers University of Technology, 412 96 Gothenburg, Sweden
| | - Filipe Liu
- CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Present Address: Mathematics and Computer Science Division, Argonne National Laboratory, Argonne, IL USA
| | - Paulo Vilaça
- SilicoLife Lda, Rua do Canastreiro 15, 4715-387 Braga, Portugal
| | - Isabel Rocha
- CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB-NOVA), Oeiras, Portugal
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Enzyme catalyzed radical dehydrations of hydroxy acids. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1824:1278-90. [PMID: 22178228 DOI: 10.1016/j.bbapap.2011.11.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2011] [Accepted: 11/28/2011] [Indexed: 11/24/2022]
Abstract
BACKGROUND The steadily increasing field of radical biochemistry is dominated by the large family of S-adenosylmethionine dependent enzymes, the so-called radical SAM enzymes, of which several new members are discovered every year. Here we report on 2- and 4-hydroxyacyl-CoA dehydratases which apply a very different method of radical generation. In these enzymes ketyl radicals are formed by one-electron reduction or oxidation and are recycled after each turnover without further energy input. Earlier reviews on 2-hydroxyacyl-CoA dehydratases were published in 2004 [J. Kim, M. Hetzel, C.D. Boiangiu, W. Buckel, FEMS Microbiol. Rev. 28 (2004) 455-468. W. Buckel, M. Hetzel, J. Kim, Curr. Opin. Chem. Biol. 8 (2004) 462-467.] SCOPE OF REVIEW The review focuses on four types of 2-hydroxyacyl-CoA dehydratases that are involved in the fermentation of amino acids by anaerobic bacteria, especially clostridia. These enzymes require activation by one-electron transfer from an iron-sulfur protein driven by hydrolysis of ATP. The review further describes the proposed mechanism that is highlighted by the identification of the allylic ketyl radical intermediate and the elucidation of the crystal structure of 2-hydroxyisocapryloyl-CoA dehydratase. With 4-hydroxybutyryl-CoA dehydratase the crystal structure, the complete stereochemistry and the function of several conserved residues around the active site could be identified. Finally potential biotechnological applications of the radical dehydratases are presented. GENERAL SIGNIFICANCE The action of the activator as an 'Archerase' shooting electrons into difficultly reducible acceptors becomes an emerging principle in anaerobic metabolism. The dehydratases may provide useful tools in biotechnology. This article is part of a Special Issue entitled: Radical SAM enzymes and Radical Enzymology.
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Parthasarathy A, Pierik AJ, Kahnt J, Zelder O, Buckel W. Substrate specificity of 2-hydroxyglutaryl-CoA dehydratase from Clostridium symbiosum: toward a bio-based production of adipic acid. Biochemistry 2011; 50:3540-50. [PMID: 21434666 DOI: 10.1021/bi1020056] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Expression of six genes from two glutamate fermenting clostridia converted Escherichia coli into a producer of glutaconate from 2-oxoglutarate of the general metabolism (Djurdjevic, I. et al. 2010, Appl. Environ. Microbiol.77, 320-322). The present work examines whether this pathway can also be used to reduce 2-oxoadipate to (R)-2-hydroxyadipic acid and dehydrate its CoA thioester to 2-hexenedioic acid, an unsaturated precursor of the biotechnologically valuable adipic acid (hexanedioic acid). 2-Hydroxyglutaryl-CoA dehydratase from Clostridium symbiosum, the key enzyme of this pathway and a potential radical enzyme, catalyzes the reversible dehydration of (R)-2-hydroxyglutaryl-CoA to (E)-glutaconyl-CoA. Using a spectrophotometric assay and mass spectrometry, it was found that (R)-2-hydroxyadipoyl-CoA, oxalocrotonyl-CoA, muconyl-CoA, and butynedioyl-CoA, but not 3-methylglutaconyl-CoA, served as alternative substrates. Hydration of butynedioyl-CoA most likely led to 2-oxosuccinyl-CoA, which spontaneously hydrolyzed to oxaloacetate and CoASH. The dehydratase is not specific for the CoA-moiety because (R)-2-hydroxyglutaryl-thioesters of N-acetylcysteamine and pantetheine served as almost equal substrates. Whereas the related 2-hydroxyisocaproyl-CoA dehydratase generated the stable and inhibitory 2,4-pentadienoyl-CoA radical, the analogous allylic ketyl radical could not be detected with muconyl-CoA and 2-hydroxyglutaryl-CoA dehydratase. With the exception of (R)-2-hydroxyglutaryl-CoA, all mono-CoA-thioesters of dicarboxylates used in this study were synthesized with glutaconate CoA-transferase from Acidaminococcus fermentans. The now possible conversion of (R)-2-hydroxyadipate via (R)-2-hydroxyadipoyl-CoA and 2-hexenedioyl-CoA to 2-hexenedioate paves the road for a bio-based production of adipic acid.
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Mack M, Bendrat K, Zelder O, Eckel E, Linder D, Buckel W. Location of the Two Genes Encoding Glutaconate Coenzyme A-Transferase at the Beginning of the Hydroxyglutarate Operon in Acidaminococcus fermentans. ACTA ACUST UNITED AC 2008. [DOI: 10.1111/j.1432-1033.1994.00t41.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Buckel W, Martins BM, Messerschmidt A, Golding BT. Radical-mediated dehydration reactions in anaerobic bacteria. Biol Chem 2005; 386:951-9. [PMID: 16218867 DOI: 10.1515/bc.2005.111] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractMost dehydratases catalyse the elimination of water from β-hydroxy ketones, β-hydroxy carboxylic acids or β-hydroxyacyl-CoA. The electron-withdrawing carbonyl functionalities acidify the α-hydrogens to enable their removal by basic amino acid side chains. Anaerobic bacteria, however, ferment amino acids via α- or γ-hydroxyacyl-CoA, dehydrations of which involve the abstraction of a β-hydrogen, which is ostensibly non-acidic (pKca. 40). Evidence is accumulating that β-hydrogens are acidified via transient conversion of the CoA derivatives to enoxy radicals by one-electron transfers, which decrease the pKto 14. The dehydrations of (R)-2-hydroxyacyl-CoA to (E)-2-enoyl-CoA are catalysed by heterodimeric [4Fe-4S]-containing dehydratases, which require reductive activation by an ATP-dependent one-electron transfer mediated by a homodimeric protein with a [4Fe-4S] cluster between the two subunits. The electron is further transferred to the substrate, yielding a ketyl radical anion, which expels the hydroxyl group and forms an enoxy radical. The dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA involves a similar mechanism, in which the ketyl radical anion is generated by one-electron oxidation. The structure of the FAD- and [4Fe-4S]-containing homotetrameric dehydratase is related to that of acyl-CoA dehydrogenases, suggesting a radical-based mechanism for both flavoproteins.
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Affiliation(s)
- Wolfgang Buckel
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, D-35032 Marburg, Germany.
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Kim J, Hetzel M, Boiangiu CD, Buckel W. Dehydration of (R)-2-hydroxyacyl-CoA to enoyl-CoA in the fermentation of alpha-amino acids by anaerobic bacteria. FEMS Microbiol Rev 2004; 28:455-68. [PMID: 15374661 DOI: 10.1016/j.femsre.2004.03.001] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2003] [Revised: 03/25/2004] [Accepted: 03/26/2004] [Indexed: 10/26/2022] Open
Abstract
Several clostridia and fusobacteria ferment alpha-amino acids via (R)-2-hydroxyacyl-CoA, which is dehydrated to enoyl-CoA by syn-elimination. This reaction is of great mechanistic interest, since the beta-hydrogen, to be eliminated as proton, is not activated (pK 40-50). A mechanism has been proposed, in which one high-energy electron acts as cofactor and transiently reduces the electrophilic thiol ester carbonyl to a nucleophilic ketyl radical anion. The 2-hydroxyacyl-CoA dehydratases are two-component systems composed of an extremely oxygen-sensitive component A, an activator, and component D, the actual dehydratase. Component A, a homodimer with one [4Fe-4S]cluster, transfers an electron to component D, a heterodimer with 1-2 [4Fe-4S]clusters and FMN, concomitant with hydrolysis of two ATP. From component D the electron is further transferred to the substrate, where it facilitates elimination of the hydroxyl group. In the resulting enoxyradical the beta-hydrogen is activated (pK14). After elimination the electron is handed-over to the next incoming substrate without further hydrolysis of ATP. The helix-cluster-helix architecture of component A forms an angle of 105 degrees, which probably opens to 180 degrees upon binding of ATP resembling an archer shooting arrows. Therefore we designated component A as 'Archerase'. Here, we describe 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans, Clostridium symbiosum and Fusobacterium nucleatum, 2-phenyllactate dehydratase from Clostridium sporogenes, 2-hydroxyisocaproyl-CoA dehydratase from Clostridium difficile, and lactyl-CoA dehydratase from Clostridium propionicum. A relative of the 2-hydroxyacyl-CoA dehydratases is benzoyl-CoA reductase from Thauera aromatica. Analogous but unrelated archerases are the iron proteins of nitrogenase and bacterial protochlorophyllide reductase. In anaerobic organisms, which do not oxidize 2-oxo acids, a second energy-driven electron transfer from NADH to ferredoxin, the electron donor of component A, has been established. The transfer is catalysed by a membrane-bound NADH-ferredoxin oxidoreductase driven by an electrochemical Na(+)-gradient. This enzyme is related to the Rnf proteins involved in Rhodobacter capsulatus nitrogen fixation.
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Affiliation(s)
- Jihoe Kim
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Unversität, Karl-von-Frisch Strasse, D-35032 Marburg, Germany
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Thamer W, Cirpus I, Hans M, Pierik AJ, Selmer T, Bill E, Linder D, Buckel W. A two [4Fe-4S]-cluster-containing ferredoxin as an alternative electron donor for 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. Arch Microbiol 2003; 179:197-204. [PMID: 12610725 DOI: 10.1007/s00203-003-0517-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2002] [Revised: 12/17/2002] [Accepted: 12/20/2002] [Indexed: 10/20/2022]
Abstract
The key step in the fermentation of glutamate by Acidaminococcus fermentans is a reversible syn-elimination of water from ( R)-2-hydroxyglutaryl-CoA to ( E)-glutaconyl-CoA catalyzed by 2-hydroxyglutaryl-CoA dehydratase, a two-component enzyme system. The actual dehydration is mediated by component D, which contains 1.0 [4Fe-4S](2+) cluster, 1.0 reduced riboflavin-5'-phosphate and about 0.1 molybdenum (VI) per heterodimer. The enzyme has to be activated by the extremely oxygen-sensitive [4Fe-4S](1+/2+)-cluster-containing homodimeric component A, which generates Mo(V) by an ATP/Mg(2+)-induced one-electron transfer. Previous experiments established that the hydroquinone state of a flavodoxin (m=14.6 kDa) isolated from A. fermentans served as one-electron donor of component A, whereby the blue semiquinone is formed. Here we describe the isolation and characterization of an alternative electron donor from the same organism, a two [4Fe-4S](1+/2+)-cluster-containing ferredoxin (m=5.6 kDa) closely related to that from Clostridium acidiurici. The protein was purified to homogeneity and almost completely sequenced; the magnetically interacting [4Fe-4S] clusters were characterized by EPR and Mössbauer spectroscopy. The redox potentials of the ferredoxin were determined as -405 mV and -340 mV. Growth experiments with A. fermentans in the presence of different iron concentrations in the medium (7-45 microM) showed that flavodoxin is the dominant electron donor protein under iron-limiting conditions. Its concentration continuously decreased from 3.5 micromol/g protein at 7 microM Fe to 0.02 micromol/g at 45 microM Fe. In contrast, the concentration of ferredoxin increased stepwise from about 0.2 micromol/g at 7-13 microM Fe to 1.1+/-0.1 micromol/g at 17-45 microM Fe.
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Affiliation(s)
- Wiebke Thamer
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, 35032 Marburg, Germany
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Hans M, Bill E, Cirpus I, Pierik AJ, Hetzel M, Alber D, Buckel W. Adenosine triphosphate-induced electron transfer in 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. Biochemistry 2002; 41:5873-82. [PMID: 11980491 DOI: 10.1021/bi020033m] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans catalyzes the chemical difficult elimination of water from (R)-2-hydroxyglutaryl-CoA to glutaconyl-CoA. The enzyme consists of two oxygen-sensitive protein components, the homodimeric activator (A) with one [4Fe-4S]1+/2+ cluster and the heterodimeric dehydratase (D) with one nonreducible [4Fe-4S]2+ cluster and reduced riboflavin 5'-monophosphate (FMNH2). For activation, ATP, Mg2+, and a reduced flavodoxin (16 kDa) purified from A. fermentans are required. The [4Fe-4S](1+/2+) cluster of component A is exposed to the solvent since it is accessible to iron chelators. Upon exchange of the bound ADP by ATP, the chelation rate is 8-fold enhanced, indicating a large conformational change. Oxidized component A exhibits ATPase activity of 6 s(-1), which is completely abolished upon reduction by one electron. UV-visible spectroscopy revealed a spontaneous one-electron transfer from flavodoxin hydroquinone (E(0)' = -430 mV) to oxidized component A, whereby the [4Fe-4S]2+ cluster of component A became reduced. Combined kinetic, EPR, and Mössbauer spectrocopic investigations exhibited an ATP-dependent oxidation of component A by component D. Whereas the [4Fe-4S]2+ cluster of component D remained in the oxidized state, a new EPR signal became visible attributed to a d1-metal species, probably Mo(V). Metal analysis with neutron activation and atomic absorption spectroscopy gave 0.07-0.2 Mo per component D. In summary, the data suggest that in the presence of ATP one electron is transferred from flavodoxin hydroquinone via the [4Fe-4S]1+/2+ cluster of component A to Mo(VI) of component D, which is thereby reduced to Mo(V). The latter may supply the electron necessary for transient charge reversal in the unusual dehydration.
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Affiliation(s)
- Marcus Hans
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Marburg, Germany
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Hans M, Buckel W, Bill E. The iron-sulfur clusters in 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. Biochemical and spectroscopic investigations. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:7082-93. [PMID: 11106419 DOI: 10.1046/j.1432-1327.2000.01809.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The reversible dehydration of (R)-2-hydroxyglutaryl-CoA to (E)-glutaconyl-CoA is catalysed by the combined action of two oxygen-sensitive enzymes from Acidaminococcus fermentans, the homodimeric component A (2 x 27 kDa) and the heterodimeric component D (45 and 50 kDa). Component A was purified to homogeneity (specific activity 25-30 s-1) using streptavidin-tag affinity chromatography. In the presence of 5 mM MgCl2 and 1 mM ADP or ATP, component A could be stabilized and stored for 4-5 days at 4 degrees C without loss of activity. The purification of component D from A. fermentans was also improved as indicated by the 1.5-fold higher specific activity (15 s-1). The content of 1.0 riboflavin 5'-phosphate (FMN) per heterodimer could be confirmed, whereas in contrast to an earlier report only trace amounts of riboflavin (< 0.1) could be detected. Each active component contains an oxygen sensitive diamagnetic [4Fe-4S]2+ cluster as revealed by UV-visible, EPR and Mössbauer spectroscopy. Reduction of the [4Fe-4S]2+ cluster in component A with dithionite yields a paramagnetic [4Fe-4S]1+ cluster with the unusual electron spin ground state S = 3/2 as indicated by strong absorption type EPR signals at high g values, g = 4-6. Spin-Hamiltonian simulations of the EPR spectra and of magnetic Mössbauer spectra were performed to determine the zero field splitting (ZFS) parameters of the cluster and the 57Fe hyperfine interaction parameters. The electronic properties of the [4Fe-4S]2+, 1+ clusters of component A are similar to those of the nitrogenase iron protein in which a [4Fe-4S]2+ cluster bridges the two subunits of the homodimeric protein. Under air component A looses its activity within seconds due to irreversible degradation of its [4Fe-4S]2+ cluster to a [2Fe-2S]2+ cluster. The [4Fe-4S]2+ cluster of component D could not be reduced to a [4Fe-4S]1+ cluster, even with excess of Ti(III)citrate or dithionite. Exposure to oxic conditions slowly converts the diamagnetic [4Fe-4S]2+ cluster of component D to a paramagnetic [3Fe-4S]+ cluster concomitant with loss of activity (30% within 24 h at 4 degrees C).
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Affiliation(s)
- M Hans
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Marburg, Germany
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Boll M, Fuchs G, Meier C, Trautwein A, Lowe DJ. EPR and Mössbauer studies of benzoyl-CoA reductase. J Biol Chem 2000; 275:31857-68. [PMID: 10903310 DOI: 10.1074/jbc.m001508200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Benzoyl-CoA reductase catalyzes the two-electron transfer from a reduced ferredoxin to the aromatic ring of benzoyl-CoA; this reaction is coupled to stoichiometrical ATP hydrolysis. A very low reduction potential (less than -1 V) is required for the first electron transfer to the aromatic ring. In this work the nature of the redox centers of purified benzoyl-CoA reductase from Thauera aromatica was studied by EPR and Mössbauer spectroscopy. The results obtained indicated the presence of three [4Fe-4S] clusters. Redox titration studies revealed that the reduction potentials of all three clusters were below -500 mV. The previously reported S = 7/2 state of the enzyme during benzoyl-CoA-independent ATPase activity (Boll, M., Albracht, S. J. P., and Fuchs, G. (1997) Eur. J. Biochem. 244, 840-851) was confirmed by Mössbauer spectroscopy. Inactivation by oxygen was associated with the irreversible conversion of part of the [4Fe-4S] clusters to [3Fe-4S] clusters. Acetylene stimulated the benzoyl-CoA-independent ATPase activity and induced novel EPR signals with g(av) >2. The presence of simple cubane clusters in benzoyl-CoA reductase as the sole redox-active metal centers demonstrates novel aspects of [4Fe-4S] clusters since they adopt the role of elemental sodium or lithium which are used as electron donors in the analogous chemical Birch reduction of aromatic rings.
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Affiliation(s)
- M Boll
- Biological Chemistry Department, John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom.
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15
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Hans M, Sievers J, Müller U, Bill E, Vorholt JA, Linder D, Buckel W. 2-hydroxyglutaryl-CoA dehydratase from Clostridium symbiosum. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 265:404-14. [PMID: 10491198 DOI: 10.1046/j.1432-1327.1999.00748.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Component D (HgdAB) of 2-hydroxyglutaryl-CoA dehydratase from Clostridium symbiosum was purified to homogeneity. It is able to use component A from Acidaminococcus fermentans (HgdC) to initiate catalysis together with ATP, Mg2+ and a strong reducing agent such as Ti(III)citrate. Component D from C. symbiosum has a 6 x higher specific activity compared with that from A. fermentans and contains a second [4Fe-4S] cluster but the same amount of riboflavin 5'-phosphate (1.0 per heterodimeric enzyme, m = 100 kDa). Mössbauer spectroscopy revealed symmetric cube-type structures of the two [4Fe-4S]2+ clusters. EPR spectroscopy showed the resistance of the clusters to reducing agents, but detected a sharp signal at g = 2. 004 probably due to a stabilized flavin semiquinone. Three genes from C. symbiosum coding for components D (hgdA and hgdB) and A (hgdC) were cloned and sequenced. Primer extension experiments indicated that the genes are transcribed in the order hgdCAB from an operon only half the size of that from A. fermentans. Sequence comparisons detected a close relationship to the dehydratase system from A. fermentans and HgdA from Fusobacterium nucleatum, as well as to putative proteins of unknown function from Archaeoglobus fulgidus. Lower, but significant, identities were found with putative enzymes from several methanogenic Archaea and Escherichia coli, as well as with the mechanistically related benzoyl-CoA reductases from the Proteobacteria Rhodopseudomonas palustris and Thauera aromatica.
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Affiliation(s)
- M Hans
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Marburg, Germany
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16
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Selmer T, Buckel W. Oxygen exchange between acetate and the catalytic glutamate residue in glutaconate CoA-transferase from Acidaminococcus fermentans. Implications for the mechanism of CoA-ester hydrolysis. J Biol Chem 1999; 274:20772-8. [PMID: 10409616 DOI: 10.1074/jbc.274.30.20772] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The exchange of oxygen atoms between acetate, glutaryl-CoA, and the catalytic glutamate residue in glutaconate CoA-transferase from Acidaminococcus fermentans was analyzed using [(18)O(2)]acetate together with matrix-assisted laser desorption/ionization time of flight mass spectrometry of an appropriate undecapeptide. The exchange reaction was shown to be site-specific, reversible, and required both glutaryl-CoA and [(18)O(2)]acetate. The observed exchange is in agreement with the formation of a mixed anhydride intermediate between the enzyme and acetate. In contrast, with a mutant enzyme, which was converted to a thiol ester hydrolyase by replacement of the catalytic glutamate residue by aspartate, no (18)O uptake from H(2)(18)O into the carboxylate was detectable. This result is in accord with a mechanism in which the carboxylate of aspartate acts as a general base in activating a water molecule for hydrolysis of the thiol ester intermediate. This mechanism is further supported by the finding of a significant hydrolyase activity of the wild-type enzyme using acetyl-CoA as substrate, whereas glutaryl-CoA is not hydrolyzed. The small acetate molecule in the substrate binding pocket may activate a water molecule for hydrolysis of the nearby enzyme-CoA thiol ester.
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Affiliation(s)
- T Selmer
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, D-35032 Marburg, Germany.
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17
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Buckel W, Golding BT. Radical species in the catalytic pathways of enzymes from anaerobes. FEMS Microbiol Rev 1998. [DOI: 10.1111/j.1574-6976.1998.tb00385.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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18
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Jacob U, Mack M, Clausen T, Huber R, Buckel W, Messerschmidt A. Glutaconate CoA-transferase from Acidaminococcus fermentans: the crystal structure reveals homology with other CoA-transferases. Structure 1997; 5:415-26. [PMID: 9083111 DOI: 10.1016/s0969-2126(97)00198-6] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Coenzyme A-transferases are a family of enzymes with a diverse substrate specificity and subunit composition. Members of this group of enzymes are found in anaerobic fermenting bacteria, aerobic bacteria and in the mitochondria of humans and other mammals, but so far none have been crystallized. A defect in the human gene encoding succinyl-CoA: 3-oxoacid CoA-transferase causes a metabolic disease which leads to severe ketoacidosis, thus reflecting the importance of this family of enzymes. All CoA-transferases share a common mechanism in which the CoA moiety is transferred from a donor (e.g. acetyl CoA) to an acceptor, (R)-2-hydroxyglutarate, whereby acetate is formed. The transfer has been described by a ping-pong mechanism in which CoA is bound to the active-site residue of the enzyme as a covalent thiol ester intermediate. We describe here the crystal structure of glutaconate CoA-transferase (GCT) from the strictly anaerobic bacterium Acidaminococcus fermentans. This enzyme activates (R)-2-hydroxyglutarate to (R)-2-hydroxyglutaryl-CoA in the pathway of glutamate fermentation. We initiated this project to gain further insight into the function of this enzyme and the structural basis for the characteristics of CoA-transferases. RESULTS The crystal structure of GCT was solved by multiple isomorphous replacement to 2.55 A resolution. The enzyme is a heterooctamer and its overall arrangement of subunits can be regarded as an (AB)4tetramer obeying 222 symmetry. Both subunits A and B belong to the open alpha/beta-protein class and can be described as a four-layered alpha/alpha/beta/alpha type with a novel composition and connectivity of the secondary structure elements. The core of subunit A consists of seven alpha/beta repeats resulting in an all parallel central beta sheet, against which helices pack from both sides. In contrast, the centre of subunit B is formed by a ninefold mixed beta sheet. In both subunits the helical C terminus is folded back onto the N-terminal domain to form the third layer of helices. CONCLUSIONS The active site of GCT is located at the interface of subunits A and B and is formed by loops of both subunits. The funnel-shaped opening to the active site has a depth and diameter of about 20 A with the catalytic residue, Glu54 of subunit B, at the bottom. The active-site glutamate residue is stabilized by hydrogen bonds. Despite very low amino acid sequence similarity, subunits A and B reveal a similar overall fold. Large parts of their structures can be spatially superimposed, suggesting that both subunits have evolved from a common ancestor.
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Affiliation(s)
- U Jacob
- Max Planck Institut für Biochemie, Abteilung Strukturforschung, Am Klopferspitz 18a, D-82152, Martinsried, Germany.
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19
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Affiliation(s)
- Dennis H. Flint
- E. I. du Pont de Nemours and Co., Central Research and Development, Experimental Station, P.O. Box 80328, Wilmington, Delaware 19880-0328
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20
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Buckel W. Unusual dehydrations in anaerobic bacteria: considering ketyls (radical anions) as reactive intermediates in enzymatic reactions. FEBS Lett 1996; 389:20-4. [PMID: 8682197 DOI: 10.1016/0014-5793(96)00530-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Dehydratases have been detected in anaerobic bacteria which use 2-, 4- or 5-hydroxyacyl-CoA as substrates and are involved in the removal of hydrogen atoms from the unactivated beta- or gamma-positions. In addition there are bacterial dehydratases acting on 1,2-diols which are substrates lacking any activating group. These enzymes contain either FAD, or flavins + iron-sulfur clusters or coenzyme B12. It has been proposed that the overall dehydrations are actually reductions followed by oxidations or vice versa mediated by these prosthetic groups. Whereas the gamma-hydrogen of 5-hydroxyvaleryl-CoA is activated by a transient two-election alpha, beta-oxidation, the other substrates are proposed to require either a transient one-electron reduction or an oxidation to a ketyl (radical anion).
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Affiliation(s)
- W Buckel
- Laboratorium für Mikrobiologie, Philipps-Universität, Marburg, Germany.
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21
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Boll M, Fuchs G. Benzoyl-coenzyme A reductase (dearomatizing), a key enzyme of anaerobic aromatic metabolism. ATP dependence of the reaction, purification and some properties of the enzyme from Thauera aromatica strain K172. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 234:921-33. [PMID: 8575453 DOI: 10.1111/j.1432-1033.1995.921_a.x] [Citation(s) in RCA: 180] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Anoxic metabolism of many aromatic compounds proceeds via the common intermediate benzoyl-CoA. Benzoyl-CoA is dearomatized by benzoyl-CoA reductase (dearomatizing) in a two-electron reduction step, possibly yielding cyclohex-1,5-diene-1-carboxyl-CoA. This process has to overcome a high activation energy and is considered a biological Birch reduction. The central, aromatic-ring-reducing enzyme was investigated for the first time in the denitrifying bacterium Thauera aromatica strain K172. A spectrophotometric assay was developed which was strictly dependent on MgATP, both with cell extract and with purified enzyme. The oxygen-sensitive new enzyme was purified 35-fold with 20% yield under anaerobic conditions in the presence of 0.25 mM dithionite. It had a native molecular mass of approximately 170 kDa and consisted of four subunits a,b,c,d of 48, 45, 38 and 32 kDa. The oligomer composition of the protein most likely is abcd. The ultraviolet/visible spectrum of the protein as isolated, but without dithionite, was characteristic for an iron-sulfur protein with an absorption maximum at 279 nm and a broad shoulder at 390 nm. The estimated molar absorption coefficient at 390 nm was 35,000 M-1 cm-1. Reduction of the enzyme by dithionite resulted in a decrease of absorbance at 390 nm, and the colour turned from greenish-brown to red-brown. The enzyme contained 10.8 +/- 1.5 mol Fe and 10.5 +/- 1.5 mol acid-labile sulfur/mol. Besides zinc (0.5 mol/mol protein) no other metals nor selenium could be detected in significant amounts. The enzyme preparation contained a flavin or flavin-like compound; the estimated content was 0.3 mol/mol enzyme. The enzyme reaction required MgATP and a strong reductant such as Ti(III). The reaction catalyzed is: benzoyl-CoA + 2 Ti(III) + n ATP-->non-aromatic acyl-CoA + 2 Ti(IV) + n ADP + n Pi. The estimated number n of ATP molecules hydrolyzed/two electrons transferred in benzoyl-CoA reduction is 2-4. In the absence of benzoyl-CoA the enzyme exhibited oxygen-sensitive ATPase activity. The enzyme was specific for Mg(2+)-ATP, other nucleoside triphosphates being inactive (< 1%). Mg2+ could be substituted to some extent by Mn2+, Fe2+ and less efficiently by Co2+. Benzoate was not reduced, whereas some fluoro, hydroxy, amino and methyl analogues of the activated benzoic acid were reduced, albeit at much lower rate; the products remain to be identified. The specific activity with reduced methyl viologen as the electron donor was 0.55 mumol min-1 mg-1 corresponding to a catalytic number of 1.6 s-1. The apparent Km values under the assay conditions (0.5 mM for both reduced and oxidized methyl viologen) of benzoyl-CoA and ATP were 15 microM and 0.6 mM, respectively. The enzyme was inactivated by ethylene, bipyridyl and, in higher concentrations, by acetylene. Benzoyl-CoA reductase also catalyzed the ATP-dependent two-electron reduction of hydroxylamine (Km 0.15 mM) and azide. Some of the properties of the enzyme are reminiscent of those of nitrogenase which similarly overcomes the high activation energy for dinitrogen reduction by coupling electron transfer to the hydrolysis of ATP.
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Affiliation(s)
- M Boll
- Angewandte Mikrobiologie, Universität Ulm, Germany
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22
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Buckel W, Keese R. Einelektronen-Redoxreaktionen von Coenzym-A-Estern in anaeroben Bakterien – ein Vorschlag für einen neuen Mechanismus. Angew Chem Int Ed Engl 1995. [DOI: 10.1002/ange.19951071321] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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23
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Muller U, Buckel W. Activation of (R)-2-hydroxyglutaryl-CoA Dehydratase from Acidaminococcus fermentans. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1432-1033.1995.tb20611.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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24
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Mack M, Bendrat K, Zelder O, Eckel E, Linder D, Buckel W. Location of the two genes encoding glutaconate coenzyme A-transferase at the beginning of the hydroxyglutarate operon in Acidaminococcus fermentans. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 226:41-51. [PMID: 7957258 DOI: 10.1111/j.1432-1033.1994.tb20024.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Glutaconate coenzyme A-transferase (Gct) from Acidaminococcus fermentans consists of two subunits (GctA, 35725 Da and GctB, 29168 Da). The N-termini sequences of both subunits were determined. DNA sequencing of a subgenomic fragment of A. fermentans revealed that the genes encoding glutaconate CoA-transferase (gctAB) are located upstream of a gene cluster formed by gcdA, hgdC, hgdA and hgdB in this order. Further upstream of gctA, a DNA sequence was detected showing significant similarities to sigma 70-type promoters from Escherichia coli. Primer-extension analysis revealed that this specific DNA sequence was indeed the location of transcription initiation in A. fermentans. The entire gene cluster, 7.3 kb in length, comprising gctAB, gcdA and hgdCAB, has tentatively been named the hydroxyglutarate operon, since the enzymes encoded by these genes are involved in the conversion of (R)-2-hydroxyglutarate to crotonyl-CoA in the pathway of glutamate fermentation by A. fermentans. The genes gctAB were expressed together in E. coli. Cell-free extracts of a transformant E. coli strain contained glutaconate CoA-transferase at a specific activity of up to 30 U/mg protein. The recombinant enzyme was purified to homogeneity with a specific activity of 130 U/mg protein by ammonium sulfate fractionation and crystallisation. The amino acid residue directly involved in catalysis was tentatively identified as E54 of the small subunit of the enzyme (GctB).
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Affiliation(s)
- M Mack
- Laboratorium für Mikrobiologie des Fachbereichs Biologie, Philipps-Universität Marburg, Germany
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25
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Scherf U, Söhling B, Gottschalk G, Linder D, Buckel W. Succinate-ethanol fermentation in Clostridium kluyveri: purification and characterisation of 4-hydroxybutyryl-CoA dehydratase/vinylacetyl-CoA delta 3-delta 2-isomerase. Arch Microbiol 1994; 161:239-45. [PMID: 8161284 DOI: 10.1007/bf00248699] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Anaerobically prepared cell extracts of Clostridium kluyveri grown on succinate plus ethanol contained high amounts of 4-hydroxybutyryl-CoA dehydratase, which catalyzes the reversible dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA. The enzyme was purified 12-fold under strictly anaerobic conditions to over 95% homogeneity and had a specific activity of 123 nkat mg-1. The finding of this dehydratase means that all of the enzymes necessary for fermentation of succinate plus ethanol by C. kluyveri have now been demonstrated to exist in this organism and confirms the proposed pathway involving a reduction of succinate via 4-hydroxybutyrate to butyrate. Interestingly, the enzyme is almost identical to the previously isolated 4-hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum. The dehydratase was revealed as being a homotetramer (m = 59 kDa/subunit), containing 2 +/- 0.2 mol FAD, 13.6 +/- 0.8 mol Fe and 10.8 +/- 1.2 mol inorganic sulfur. The enzyme was irreversibly inactivated after exposure to air. Reduction by sodium dithionite also yielded an inactive enzyme which could be reactivated, however, up to 84% by oxidation with potassium hexacyanoferrate(III). The enzyme possesses an intrinsic vinylacetyl-CoA isomerase activity which was also found in 4-hydroxybutyryl-CoA dehydratase from C. aminobutyricum. Moreover, the N-terminal sequences of the dehydratases from both organisms were found to be 63% identical.
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Affiliation(s)
- U Scherf
- Laboratorium für Mikrobiologie des Fachbereiches Biologie der Philipps-Universität, Marburg, Germany
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26
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Flint D, Tuminello J, Emptage M. The inactivation of Fe-S cluster containing hydro-lyases by superoxide. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)41538-4] [Citation(s) in RCA: 171] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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27
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Bendrat K, Müller U, Klees AG, Buckel W. Identification of the gene encoding the activator of (R)-2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans by gene expression in Escherichia coli. FEBS Lett 1993; 329:329-31. [PMID: 8365476 DOI: 10.1016/0014-5793(93)80247-r] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
(R)-2-Hydroxyglutaryl-CoA dehydratase (HGDA/B) from Acidaminococcus fermentans requires an activator protein for activity. This activator (HGDC) has not yet been purified from its natural source due to its low concentration combined with an extreme sensitivity towards oxygen. Gene expression in Escherichia coli identified an open reading frame (780 bp) as the gene encoding HGDC. Dehydratase activity was stimulated at least tenfold by cell-free extracts of E. coli cells transformed with a plasmid carrying hgdC. On the chromosome the hgdC gene is located just before hgdA and hgdB.
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Affiliation(s)
- K Bendrat
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität, Marburg, Germany
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28
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Scherf U, Buckel W. Purification and properties of an iron-sulfur and FAD-containing 4-hydroxybutyryl-CoA dehydratase/vinylacetyl-CoA delta 3-delta 2-isomerase from Clostridium aminobutyricum. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 215:421-9. [PMID: 8344309 DOI: 10.1111/j.1432-1033.1993.tb18049.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
4-Hydroxybutyryl-CoA dehydratase, the key enzyme in the metabolism of gamma-aminobutyrate in Clostridium aminobutyricum, represents approximately 15-25% of the soluble protein. The enzyme was purified to homogeneity under anaerobic conditions to a specific activity of 209 nkat mg-1. The dehydratase catalyses the reversible conversion of 4-hydroxybutyryl-CoA (Km = 50 microM) to crotonyl-CoA and possesses a probably intrinsic vinylacetyl-CoA delta 3-delta 2-isomerase with a specific activity of 223 nkat mg-1. The equilibrium of the reversible dehydration was determined from both sides as K = [crotonyl-CoA]/[4-hydroxybutyryl-CoA] = 4.2 +/- 0.3. Cyclopropylcarboxyl-CoA was not converted to crotonyl-CoA. The native enzyme has an apparent molecular mass of 232 kDa and is composed of four apparently identical subunits (molecular mass = 56 kDa), indicating a homotetrameric structure. Under anaerobic conditions the active enzyme revealed a brown colour and contained 2 +/- 0.2 mol FAD (64 +/- 5% oxidized), 16 +/- 0.8 mol Fe and 14.4 +/- 1.2 mol inorganic sulfur, which probably form iron-sulfur clusters. Exposure to air resulted initially in a slight activation followed by irreversible inactivation. Concomitantly the vinylacetyl-CoA delta-isomerase activity was lost and the colour of the enzyme changed to yellow. Reduction by sodium dithionite yielded inactive enzyme which could be completely reactivated by oxidation with potassium hexacyanoferrate(III). The data indicate that the active enzyme contains oxidized FAD despite its sensitivity towards oxygen. During the dehydration a non activated C-H bond at C-3 of 4-hydroxybutyryl-CoA has to be cleaved. A putative mechanism for 4-hydroxybutyryl-CoA dehydratase is proposed in which this cleavage is achieved by a FAD-dependent oxidation of 4-hydroxybutyryl-CoA to 4-hydroxycrotonyl-CoA. In a second step the hydroxyl group is substituted by a hydride derived from the now reduced FAD in an SN2' reaction leading to vinylacetyl-CoA. Finally isomerisation yields crotonyl-CoA. 4-Hydroxybutyryl-CoA dehydratase is quite distinct from 3-hydroxyacyl-CoA dehydratase (crotonase) and 2-hydroxyacyl-CoA dehydratases. Contrary to the latter enzyme [e.g. (R)-lactyl-CoA dehydratase and (R)-2-hydroxyglutaryl-CoA dehydratase] which are composed of three different subunits and similarly catalyse the cleavage of a non activated C-H bond at C-3, 4-hydroxybutyryl-CoA dehydratase does not require ATP, MgCl2 and Ti(III)citrate for activity. Furthermore 4-hydroxybutyryl-CoA dehydratase is not inactivated by oxidants such as 5 mM 4-nitrophenol, 5 mM chloramphenicol and 5 mM hydroxylamine.
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Affiliation(s)
- U Scherf
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität Marburg, Germany
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29
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Flint D, Emptage M, Finnegan M, Fu W, Johnson M. The role and properties of the iron-sulfur cluster in Escherichia coli dihydroxy-acid dehydratase. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)82394-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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30
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Seyfried B, Tschech A, Fuchs G. Anaerobic oxidation of phenylacetate and 4-hydroxyphenylacetate to benzoyl-coenzyme A and CO2 in denitrifying Pseudomonas sp. Evidence for an alpha-oxidation mechanism. Arch Microbiol 1993; 159:563-73. [PMID: 8352646 DOI: 10.1007/bf00249036] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Anaerobic degradation of (4-hydroxy)phenylacetate in denitrifying Pseudomonas sp. was investigated. Evidence is presented for alpha-oxidation of the coenzyme A (CoA)-activated carboxymethyl side chain, a reaction which has not been described. The C6-C2 compounds are degraded to benzoyl-CoA and furtheron to CO2 via the following intermediates: Phenylacetyl-CoA, phenylglyoxylate, benzoyl-CoA plus CO2; 4-hydroxyphenylacetyl-CoA, 4-hydroxyphenylglyoxylate, 4-hydroxybenzoyl-CoA plus CO2, benzoyl-CoA. Trace amounts of mandelate possibly derived from mandelyl-CoA were detected during phenylacetate degradation in vitro. The reactions are catalyzed by (i) phenylacetate-CoA ligase which converts phenylacetate to phenylacetyl-CoA and by a second enzyme for 4-hydroxyphenylacetate; (ii) a (4-hydroxy)-phenylacetyl-CoA dehydrogenase system which oxidizes phenylacetyl-CoA to (4-hydroxy)phenylglyoxylate plus CoA; and (iii) (4-hydroxy)phenylglyoxylate: acceptor oxidoreductase (CoA acylating) which catalyzes the oxidative decarboxylation of (4-hydroxy)phenylglyoxylate to (4-hydroxy)benzoyl-CoA and CO2. (iv) The degradation of 4-hydroxyphenylacetate in addition requires the reductive dehydroxylation of 4-hydroxybenzoyl-CoA to benzoyl-CoA, catalyzed by 4-hydroxybenzoyl-CoA reductase (dehydroxylating). The whole cell regulation of these enzyme activities supports the proposed pathway. An ionic mechanism for anaerobic alpha-oxidation of the CoA-activated carboxymethyl side chain is proposed.
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31
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Bendrat K, Buckel W. Cloning, sequencing and expression of the gene encoding the carboxytransferase subunit of the biotin-dependent Na+ pump glutaconyl-CoA decarboxylase from Acidaminococcus fermentans in Escherichia coli. EUROPEAN JOURNAL OF BIOCHEMISTRY 1993; 211:697-702. [PMID: 8382157 DOI: 10.1111/j.1432-1033.1993.tb17598.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
1. The primary sodium-ion pump glutaconyl-CoA decarboxylase (GCD) from Acidaminococcus fermentans is composed of four subunits: GCDA, the carboxytransferase (65 kDa), GCDB, the carboxylyase (36 kDa), GCDC, the biotin carrier (24 kDa) and GCDD (14 kDa) of unknown function. A genomic library of A. fermentans was screened with an antiserum raised against whole GCD. A clone giving the strongest reaction in an immunoassay contained a 12-kbp genomic fragment from A. fermentans and was analysed further. An oligonucleotide deduced from the N-terminus of GCDA was used for probing the corresponding gene gcdA. It is 1761 bp in length and encodes for a protein of 64.3 kDa. Both partial amino acid sequences obtained from GCDA, the N-terminus as well as an internal tryptic peptide, were detected in the open reading frame (ORF) of gcdA. 2. Sequencing of the flanking regions revealed three adjacent ORF (ORF1-3) which do not code for any of the peptide sequences known of the other GCD subunits. The ORF downstream of gcdA (ORF3) is followed by hgdA and hgdB coding for 2-hydroxyglutaryl-CoA dehydratase, the preceding enzyme of the pathway of glutamate fermentation. Our results suggest that at least these three genes of the hydroxyglutarate pathway are organised in an operon and that the genes of the other GCD subunits from which peptide sequences are known (GCDB and GCDC) are not located adjacent to gcdA. 3. gcdA was amplified from genomic DNA using the polymerase chain reaction and cloned into the expression vector pJF118HE. Active GCDA subunit (up to 2.8 nkat/mg protein), catalysing the biotin-dependent formation of crotonyl-CoA from glutaconyl-CoA, was obtained in cell-free extracts of Escherichia coli DH5 alpha by moderately inducing the tac promoter of pJF118HE with 25-100 microM isopropyl-1-thio-beta-D-galactoside. Strong induction (1 mM isopropyl-1-thio-beta-D-galactoside) led to the formation of inclusion bodies from which GCDA could not be reactivated. The apparent Km = 51 mM for free biotin of the expressed GCDA subunit with V = 1.9 nkat/mg protein is similar to that of butanol-treated GCD composed of GCDA and GCDC (apparent Km = 40 mM). Biocytin was found to be a somewhat better carboxy acceptor for the expressed GCDA subunit (apparent Km = 13 mM; V = 1.0 nkat/mg protein). 4. Native GCD and expressed GCDA were treated with 2 mM N-ethylmaleimide showing different kinetics of inactivation: GCD lost half of its activity within 6 min, whereas expressed GCDA required 21 min.
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Affiliation(s)
- K Bendrat
- Laboratorium für Mikrobiologie, Philipps-Universität Marburg, Federal Republic of Germany
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Both B, Buckel W, Kroppenstedt R, Stackebrandt E. Phylogenetic and chemotaxonomic characterization ofAcidaminococcus fermentans. FEMS Microbiol Lett 1992. [DOI: 10.1111/j.1574-6968.1992.tb05431.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Klees AG, Linder D, Buckel W. 2-Hydroxyglutaryl-CoA dehydratase from Fusobacterium nucleatum (subsp. nucleatum): an iron-sulfur flavoprotein. Arch Microbiol 1992; 158:294-301. [PMID: 1417419 DOI: 10.1007/bf00245248] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Anaerobically prepared cell-free extracts from Fusobacterium nucleatum contain 2-hydroxyglutaryl-CoA dehydratase with a specific activity of 20 nkat mg-1. The enzyme was purified 24-fold to a specific activity of 480 nkat mg-1 by anion exchange chromatography, gel filtration and chromatography on Blue-Sepharose. The activity of the purified enzyme was strictly dependent on the reductant Ti(III)citrate and stimulated 25-fold by 0.15 mM ATP and 5 mM MgCl2. ATP is hydrolysed to ADP during incubation with 2-hydroxyglutaryl-CoA dehydratase in the presence or absence of the substrate. The enzyme is extremely sensitive towards oxygen and is inhibited by 10 microM chloramphenicol, 10 microM 2,4-dinitrophenol or 0.15 mM hydroxylamine. The pure enzyme consists of three subunits alpha (49 kDa), beta (39 kDa) and gamma (24 kDa) in approximately equal amounts. In this respect the enzyme differs from the related 2-hydroxyglutaryl-CoA dehydratase from Acidaminococcus fermentans and lactyl-CoA dehydratase from Clostridium propionicum both of which are composed of only two subunits with sizes comparable to those of alpha and beta but require an additional protein for activity. The relative molecular mass of the native enzyme of about 100 kDa suggests a trimeric alpha beta gamma-structure. The homogeneous enzyme contains riboflavin (0.5 mol/112 kDa), iron and sulfur (3.5 mol/112 kDa each). Polyclonal antibodies directed against the 2-hydroxyglutaryl-CoA dehydratase from A. fermentans did not crossreact with cell free extracts or purified dehydratase from F. nucleatum. A comparison of the N-terminal amino acid sequences of the dehydratase subunits from A. fermentans and F. nucleatum, however, showed some similarities in the beta-subunits.
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Affiliation(s)
- A G Klees
- Laboratorium für Mikrobiologie des Fachbereichs Biologie, Philipps-Universität, Marburg, Federal Republic of Germany
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Fischer R, Gärtner P, Yeliseev A, Thauer RK. N5-methyltetrahydromethanopterin: coenzyme M methyltransferase in methanogenic archaebacteria is a membrane protein. Arch Microbiol 1992; 158:208-17. [PMID: 1444718 DOI: 10.1007/bf00290817] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
An assay is described that allows the direct measurement of the enzyme activity catalyzing the transfer of the methyl group from N5-methyltetrahydromethanopterin (CH3-H4MPT) to coenzyme M (H-S-CoM) in methanogenic archaebacteria. With this method the topology, the partial purification, and the catalytic properties of the methyltransferase in methanol- and acetate-grown Methanosarcina barkeri and in H2/CO(2)-grown Methanobacterium thermoautotrophicum were studied. The enzyme activity was found to be associated almost completely with the membrane fraction and to require detergents for solubilization. The transferase activity in methanol-grown M. barkeri was studied in detail. The membrane fraction exhibited a specific activity of CH3-S-CoM formation from CH3-H4MPT (apparent Km = 50 microM) and H-S-CoM (apparent Km = 250 microM) of approximately 0.6 mumol.min-1.mg protein-1. For activity the presence of Ti(III) citrate (apparent Km = 15 microM) and of ATP (apparent Km = 30 microM) were required in catalytic amounts. Ti(III) could be substituted by reduced ferredoxin. ATP could not be substituted by AMP, CTP, GTP, S-adenosylmethionine, or by ATP analogues. The membrane fraction was methylated by CH3-H4MPT in the absence of H-S-CoM. This methylation was dependent on Ti(III) and ATP. The methylated membrane fraction catalyzed the methyltransfer from CH3-H4MPT to H-S-CoM in the absence of ATP and Ti(III). Demethylation in the presence of H-S-CoM also did not require Ti(III) or ATP. Based on these findings a mechanism for the methyltransfer reaction and for the activation of the enzyme is proposed.
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Affiliation(s)
- R Fischer
- Laboratorium für Mikrobiologie des Fachbereichs Biologie, Philipps-Universität Marburg, Federal Republic of Germany
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Hofmeister AE, Buckel W. (R)-lactyl-CoA dehydratase from Clostridium propionicum. Stereochemistry of the dehydration of (R)-2-hydroxybutyryl-CoA to crotonyl-CoA. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 206:547-52. [PMID: 1597194 DOI: 10.1111/j.1432-1033.1992.tb16958.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
1. A new two-step method for purifying component E II of lactyl-CoA dehydratase was developed. The source of the enzyme was Clostridium propionicum grown on either D,L-alanine or L-threonine. No difference in these preparations was observed whether during purification or by SDS/PAGE of the pure enzymes. Both preparations exhibited similar activities towards (R)-lactyl-CoA as well as towards (R)-2-hydroxybutyryl-CoA, the latter being the superior substrate. 2. Three species of (2R)-2-hydroxybutyrate labelled with 3H at C3 were prepared containing 96%, 37% and 63% of the 3H in the 3S-position. By incubation of these species with acetyl-CoA, propionate CoA-transferase and lactyl-CoA dehydratase 104%, 32% and 70% of the 3H, respectively, was release as 3HOH. The data indicate that stereospecific abstraction of the 3Si hydrogen of (2R)-2-hydroxybutyryl-CoA during the dehydration. 3. The identity of the product of the dehydration as crotonyl-CoA was established by the combined action of the enzymes crotonase and (S)-3-hydroxyacyl-CoA dehydrogenase. The results indicate that the elimination of water from (R)-2-hydroxybutyryl-CoA occurs in a syn mode. 4. All enzyme activities necessary for the conversion of L-threonine via (R)-2-hydroxybutyryl-CoA to butyrate were detected in cell-free extracts of C. propionicum. 5. A new mechanism for the dehydration of lactyl-CoA is proposed.
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Affiliation(s)
- A E Hofmeister
- Laboratorium für Mikrobiologie, Fachbereichs Biologie, Philipps-Universität, Marburg, Federal Republic of Germany
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Cammack R. Iron—Sulfur Clusters in Enzymes: Themes and Variations. ADVANCES IN INORGANIC CHEMISTRY 1992. [DOI: 10.1016/s0898-8838(08)60066-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Wächtershäuser G. Groundworks for an evolutionary biochemistry: the iron-sulphur world. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1992; 58:85-201. [PMID: 1509092 DOI: 10.1016/0079-6107(92)90022-x] [Citation(s) in RCA: 359] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Scherf U, Buckel W. Purification and properties of 4-hydroxybutyrate coenzyme A transferase from Clostridium aminobutyricum. Appl Environ Microbiol 1991; 57:2699-702. [PMID: 1768145 PMCID: PMC183643 DOI: 10.1128/aem.57.9.2699-2702.1991] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
A new coenzyme A (CoA)-transferase from the anaerobe Clostridium aminobutyricum catalyzing the formation of 4-hydroxybutyryl-CoA from 4-hydroxybutyrate and acetyl-CoA is described. The enzyme was purified to homogeneity by standard techniques, including fast protein liquid chromatography under aerobic conditions. Its molecular mass was determined to be 110 kDa, and that of the only subunit was determined to be 54 kDa, indicating a homodimeric structure. Besides acetate and acetyl-CoA, the following substrates were detected (in order of decreasing kcat/Km): 4-hydroxybutyryl-CoA, butyryl-CoA and propionyl-CoA, vinyl-acetyl-CoA (3-butenoyl-CoA), and 5-hydroxyvaleryl-CoA. In an indirect assay the corresponding acids were also found to be substrates; however, DL-lactate, DL-2-hydroxybutyrate, DL-3-hydroxybutyrate, crotonate, and various dicarboxylates were not.
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Affiliation(s)
- U Scherf
- Laboratorium für Mikrobiologie im Fachbereich Biologie, Philipps-Universität, Marburg, Germany
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Eikmanns U, Buckel W. Crystalline green 5-hydroxyvaleryl-CoA dehydratase from Clostridium aminovalericum. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 197:661-8. [PMID: 2029896 DOI: 10.1111/j.1432-1033.1991.tb15956.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A green enzyme from Clostridium aminovalericum with valeryl-CoA dehydrogenase activity was purified to homogeneity (169 +/- 3 kDa) and crystallized. By SDS/PAGE, one type of subunit (42 kDa) was detected indicating a homotetrameric structure. The unusual ultraviolet/visible spectrum of the green enzyme (maxima at 394 nm, 438 nm and 715 nm) was converted to a normal flavoprotein spectrum either by reduction with dithionite and reoxidation under air, or by removal of the prosthetic group at pH 2 and reconstitution with FAD (not FMN). Besides FAD (4 mol/169 kDa), the enzyme contained 4 mol of a CoA ester which was similar but not identical to 5-hydroxy-2-pentenoyl-CoA. The reconstituted holoenzyme as well as the native green enzyme, but not the apoenzyme, catalysed the reversible dehydration of 5-hydroxyvaleryl-CoA to 4-pentenoyl-CoA in the absence of an external electron acceptor. In its presence (preferentially ferricenium ion), the green or yellow enzyme catalysed the formation of (E)-5-hydroxy-2-pentenoyl-CoA and 2,4-pentadienoyl-CoA either from 4-pentenoyl-CoA or from 5-hydroxyvaleryl-CoA. The reversible hydration of 2,4-pentadienoyl-CoA to (E)-5-hydroxy-2-pentenoyl-CoA was mediated by both enzymes as well as by the apoenzyme in the absence of FAD. Hydration of 4-pentenoate in 2H2O yielded optically active 5-hydroxy[2,4-2H2]valerate by the combined action of 5-hydroxyvalerate CoA-transferase, the green dehydratase and catalytical amounts of acetyl-CoA. The data show that the reversible hydration of the isolated double bond of 4-pentenoyl-CoA to 5-hydroxyvaleryl-CoA. which apparently violates the Markovnikov rule, is preceded by oxidation to 2,4-pentadienoyl-CoA. The latter compound, a vinyl analogue of 2-enoyl-CoA, is then easily hydrated to (E)-5-hydroxy-2-pentenoyl-CoA and finally reduced to 5-hydroxyvaleryl-CoA.
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Affiliation(s)
- U Eikmanns
- Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps-Universität Marburg, Federal Republic of Germany
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Howard JB, Rees DC. Perspectives on non-heme iron protein chemistry. ADVANCES IN PROTEIN CHEMISTRY 1991; 42:199-280. [PMID: 1793006 DOI: 10.1016/s0065-3233(08)60537-9] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- J B Howard
- Department of Biochemistry, University of Minnesota School of Medicine, Minneapolis 55455
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Willadsen P, Buckel W. Assay of 4-hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum. FEMS Microbiol Lett 1990; 58:187-91. [PMID: 2227355 DOI: 10.1111/j.1574-6968.1990.tb13976.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
It has been proposed that Clostridium aminobutyricum contains an enzyme catalyzing an unusual reaction: the dehydration of 4-hydroxybutyryl-CoA to vinylacetyl-CoA. 4-Hydroxy-[3-3H]butyric acid has been prepared which allows the activity of this enzyme to be assayed in the presence of acetyl-CoA under anaerobic conditions by the release of tritiated water. Initial characterization of the enzyme from C. aminobutyricum has shown it to be largely membrane or particle bound in the crude lysates. It can be solubilized in detergent. It is inactivated by oxygen, but stable under anaerobic conditions. Only 49 +/- 2% of the label is removed after enzyme-catalyzed equilibration with water. This stereospecific release is consistent with the formation of vinylacetyl-CoA and excludes a vitamin B12 coenzyme-dependent rearrangement to 3-hydroxybutyryl-CoA followed by dehydration to crotonyl-CoA.
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Affiliation(s)
- P Willadsen
- Laboratorium für Mikrobiologie im Fachbereich Biologie der Philipps-Universität Marburg, F.R.G
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Beinert H, Kennedy MC. 19th Sir Hans Krebs lecture. Engineering of protein bound iron-sulfur clusters. A tool for the study of protein and cluster chemistry and mechanism of iron-sulfur enzymes. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 186:5-15. [PMID: 2598939 DOI: 10.1111/j.1432-1033.1989.tb15170.x] [Citation(s) in RCA: 182] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
An increasing number of iron-sulfur (Fe-S) proteins are found in which the Fe-S cluster is not involved in net electron transfer, as it is in the majority of Fe-S proteins. Most of the former are (de)hydratases, of which the most extensively studied is aconitase. Approaches are described and discussed by which the Fe-S cluster of this enzyme could be brought into states of different structure, ligation, oxidation and isotope composition. The species, so obtained, provided the basis for spectroscopic and chemical investigations. Results from studies by protein chemistry, EPR, Mössbauer, 1H, 2H and 57Fe electron-nuclear double resonance spectroscopy are described. Conclusions, which bear on the electronic structure of the Fe-S cluster, enzyme-substrate interaction and the enzymatic mechanism, were derived from a synopsis of the recent work described here and of previous contributions from several laboratories. These conclusions are discussed and summarized in a final section.
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Affiliation(s)
- H Beinert
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226
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Bell PJ, Andrews SC, Sivak MN, Guest JR. Nucleotide sequence of the FNR-regulated fumarase gene (fumB) of Escherichia coli K-12. J Bacteriol 1989; 171:3494-503. [PMID: 2656658 PMCID: PMC210076 DOI: 10.1128/jb.171.6.3494-3503.1989] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The nucleotide sequence of a 3,162-base-pair (bp) segment of DNA containing the FNR-regulated fumB gene, which encodes the anaerobic class I fumarase (FUMB) of Escherichia coli, was determined. The structural gene was found to comprise 1,641 bp, 547 codons (excluding the initiation and termination codons), and the gene product had a predicted Mr of 59,956. The amino acid sequence of FUMB contained the same number of residues as did that of the aerobic class I fumarase (FUMA), and there were identical amino acids at all but 56 positions (89.8% identity). There was no significant similarity between the class I fumarases and the class II enzyme (FUMC) except in one region containing the following consensus: Gly-Ser-Xxx-Ile-Met-Xxx-Xxx-Lys-Xxx-Asn. Some of the 56 amino acid substitutions must be responsible for the functional preferences of the enzymes for malate dehydration (FUMB) and fumarate hydration (FUMA). Significant similarities between the cysteine-containing sequence of the class I fumarases (FUMA and FUMB) and the mammalian aconitases were detected, and this finding further supports the view that these enzymes are all members of a family of iron-containing hydrolyases. The nucleotide sequence of a 1,142-bp distal sequence of an unidentified gene (genF) located upstream of fumB was also defined and found to encode a product that is homologous to the product of another unidentified gene (genA), located downstream of the neighboring aspartase gene (aspA).
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Affiliation(s)
- P J Bell
- Department of Microbiology, University of Sheffield, United Kingdom
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Dutscho R, Wohlfarth G, Buckel P, Buckel W. Cloning and sequencing of the genes of 2-hydoxyglutaryl-CoA dehydratase from Acidaminococcus fermentans. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 181:741-6. [PMID: 2659350 DOI: 10.1111/j.1432-1033.1989.tb14786.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Two genomic libraries from Acidaminococcus fermentans DNA constructed with the lambda vectors gt11 and EMBL 3 were screened with antisera raised against 2-hydroxyglutaryl-CoA dehydratase. Two clones giving the strongest reaction in the immunoassay were analyzed further, one was a lambda gt11 clone with an insert of 2050 bp and one was a lambda EMBL-3 clone with an insert of approximately 11,000 bp. Escherichia coli cells infected with the lambda gt11 clone expressed the alpha subunit of the dehydratase (Mr, 53,870), whereas with the lambda EMBL-3 clone, the alpha and beta subunits (Mr, 41,857) were detected on Western blots. Restriction fragments of both clones were subcloned in pUC 8 and sequenced by the chain termination method. Thus the complete sequence of the genes of both subunits, hgdA (alpha) and hgdB (beta) were obtained. The genes have the following order: A-B, with an intergenic region of only 2 bp. The deduced amino acid sequences for the alpha and beta subunits were confirmed by four peptides sequenced by protein chemical methods. Both chains are extremely rich in cysteine (13 in alpha, including a CNC and two CC clusters, and nine in beta) but no similarities to other known protein sequences were found.
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Affiliation(s)
- R Dutscho
- Fachbereich Biologie, Philipps-Universität, Marburg, Federal Republic of Germany
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Thauer RK. Citric-acid cycle, 50 years on. Modifications and an alternative pathway in anaerobic bacteria. EUROPEAN JOURNAL OF BIOCHEMISTRY 1988; 176:497-508. [PMID: 3049083 DOI: 10.1111/j.1432-1033.1988.tb14307.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Many anaerobic bacteria can completely oxidize organic matter to CO2 with either sulfur, sulfate, or protons as electron acceptor. The sulfur-reducing bacteria and one genus of sulfate reducers use a modified citric-acid cycle with a novel anaplerotic sequence as pathway of terminal respiration. All other anaerobes use an alternative pathway, in which carbon monoxide dehydrogenase is a key enzyme and in which acetyl-CoA is cleaved into two C1 units at the oxidation level of CH3OH and CO. Thus almost 50 years after the discovery of the citric acid cycle by Hans Krebs in 1937, a second pathway for acetyl-CoA oxidation was found.
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Affiliation(s)
- R K Thauer
- Laboratorium für Mikrobiologie, Philipps-Universität, Marburg, Federal Republic of Germany
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Immunocytochemical localization of two key enzymes of the 2-hydroxyglutarate pathway of glutamate fermentation in Acidaminococcus fermentans. Arch Microbiol 1988. [DOI: 10.1007/bf00422295] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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