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Fang S, Cao W, Wu Q, Cheng S, Jin H, Pang H, Zhou A, Feng L, Cao J, Luo J. Dynamic microbiome disassembly and evolution induced by antimicrobial methylisothiazolinone in sludge anaerobic fermentation for volatile fatty acids generation. WATER RESEARCH 2024; 251:121139. [PMID: 38237458 DOI: 10.1016/j.watres.2024.121139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/11/2024] [Accepted: 01/14/2024] [Indexed: 02/12/2024]
Abstract
In the post-COVID-19 pandemic era, various antimicrobials have emerged and concentrated in waste-activated sludge (WAS), affecting the biological treatment of WAS. However, there is still a knowledge gap in the dynamic response and adaptive mechanism of anaerobic microbiome under exogenous antimicrobial stress. This study found that methylisothiazolinone (MIT, as a typic antimicrobial) caused an interesting lag effect on the volatile fatty acids (VFAs) promotion in the WAS anaerobic fermentation process. MIT was effective to disintegrate the extracellular polymeric substances (EPS), and those functional anaerobic microorganisms were easily exposed and negatively impacted by the MIT interference after the loss of protective barriers. Correspondingly, the ecological interactions and microbial metabolic functions related to VFA biosynthesis (e.g., pyruvate metabolism) were downregulated at the initial stage. The syntrophic consortia gradually adapted to the interference and attenuated the MIT stress by activating chemotaxis and resistance genes (e.g., excreting, binding, and inactivating). Due to the increased bioavailable substrates in the fermentation systems, the dominant microorganisms (i.e., Clostridium and Caloramator) with both VFAs production and MIT-tolerance functions have been domesticated. Moreover, MIT disrupted the syntrophic interaction between acetogens and methanogens and totally suppressed methanogens' metabolic activities. The VFA production derived from WAS anaerobic fermentation was therefore enhanced due to the interference of antimicrobial MIT stress. This work deciphered dynamic changes and adaptive evolution of anaerobic syntrophic consortia in response to antimicrobial stress and provided guidance on the evaluation and control of the ecological risks of exogenous pollutants in WAS treatment.
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Affiliation(s)
- Shiyu Fang
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China
| | - Wangbei Cao
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China
| | - Qian Wu
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China
| | - Song Cheng
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China
| | - Hongqi Jin
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China
| | - Heliang Pang
- School of Environmental and Municipal Engineering, Xi 'an University of Architecture and Technology, Xi 'an 710055, China
| | - Aijuan Zhou
- College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China
| | - Leiyu Feng
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
| | - Jiashun Cao
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China
| | - Jingyang Luo
- Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098, China; College of Environment, Hohai University, Nanjing 210098, China.
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2
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The Role of Acetate Kinase in the Human Parasite Entamoeba histolytica. PARASITOLOGIA (BASEL, SWITZERLAND) 2022; 2:147-159. [PMID: 36872919 PMCID: PMC9983610 DOI: 10.3390/parasitologia2020014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The human parasite Entamoeba histolytica, which causes approximately 100 million cases of amoebic dysentery each year, relies on glycolysis as the major source of ATP production from glucose as it lacks a citric acid cycle and oxidative phosphorylation. Ethanol and acetate, the two major glycolytic end products for E. histolytica, are produced at a ratio of 2:1 under anaerobic conditions, creating an imbalance between NADH production and utilization. In this study we investigated the role of acetate kinase (ACK) in acetate production during glycolysis in E. histolytica metabolism. Analysis of intracellular and extracellular metabolites demonstrated that acetate levels were unaffected in an ACK RNAi cell line, but acetyl-CoA levels and the NAD+/NADH ratio were significantly elevated. Moreover, we demonstrated that glyceraldehyde 3-phosphate dehydrogenase catalyzes the ACK-dependent conversion of acetaldehyde to acetyl phosphate in E. histolytica. We propose that ACK is not a major contributor to acetate production, but instead provides a mechanism for maintaining the NAD+/NADH balance during ethanol production in the extended glycolytic pathway.
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3
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Biosynthesis of butyrate from methanol and carbon monoxide by recombinant Acetobacterium woodii. Int Microbiol 2022; 25:551-560. [PMID: 35179672 PMCID: PMC9307552 DOI: 10.1007/s10123-022-00234-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 12/21/2021] [Accepted: 01/11/2022] [Indexed: 10/27/2022]
Abstract
Methanol is one of the most widely produced organic substrates from syngas and can serve as a bio-feedstock to cultivate acetogenic bacteria which allows a major contribution to reducing greenhouse gas. Acetobacterium woodii is one of the very few acetogens that can utilize methanol to produce acetate as sole product. Since A. woodii is genetically tractable, it is an interesting candidate to introduce recombinant pathways for production of bio-commodities from methanol. In this study, we introduced the butyrate production operon from a related acetogen, Eubacterium callanderi KIST612, into A. woodii and show a stable production of butyrate from methanol. This study also reveals how butyrate production by recombinant A. woodii strains can be enhanced with addition of electrons in the form of carbon monoxide. Our results not only show a stable expression system of non-native enzymes in A. woodii but also increase in the product spectrum of A. woodii to compounds with higher economic value.
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Kim Y, Lama S, Agrawal D, Kumar V, Park S. Acetate as a potential feedstock for the production of value-added chemicals: Metabolism and applications. Biotechnol Adv 2021; 49:107736. [PMID: 33781888 DOI: 10.1016/j.biotechadv.2021.107736] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 02/22/2021] [Accepted: 03/19/2021] [Indexed: 10/21/2022]
Abstract
Acetate is regarded as a promising carbon feedstock in biological production owing to its possible derivation from C1 gases such as CO, CO2 and methane. To best use of acetate, comprehensive understanding of acetate metabolisms from genes and enzymes to pathways and regulations is needed. This review aims to provide an overview on the potential of acetate as carbon feedstock for industrial biotechnology. Biochemical, microbial and biotechnological aspects of acetate metabolism are described. Especially, the current state-of-the art in the production of value-added chemicals from acetate is summarized. Challenges and future perspectives are also provided.
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Affiliation(s)
- Yeonhee Kim
- School of Energy and Chemical Engineering, UNIST, 50, UNIST-gil, Ulsan 44919, Republic of Korea
| | - Suman Lama
- School of Energy and Chemical Engineering, UNIST, 50, UNIST-gil, Ulsan 44919, Republic of Korea
| | - Deepti Agrawal
- Biochemistry and Biotechnology Area, Material Resource Efficiency Division, CSIR- Indian Institute of Petroleum, Mohkampur, Dehradun 248005, India
| | - Vinod Kumar
- Centre for Climate and Environmental Protection, School of Water, Energy and Environment, Cranfield University, Cranfield, MK430AL, United Kingdom.
| | - Sunghoon Park
- School of Energy and Chemical Engineering, UNIST, 50, UNIST-gil, Ulsan 44919, Republic of Korea.
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Bachochin MJ, Van Allen M, Barber RD. Characterization of a Rhodobacter sphaeroides primary fatty acid kinase. Arch Microbiol 2020; 203:861-864. [PMID: 33040182 DOI: 10.1007/s00203-020-02055-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 09/03/2020] [Accepted: 09/15/2020] [Indexed: 11/25/2022]
Abstract
Widely distributed among prokaryotes, short chain fatty acid kinases provide a path for fatty acid entry into central metabolic pathways. These enzymes catalyze the reversible, ATP-dependent synthesis of acyl-phosphates, which leads to the production of acyl-CoA derivatives by a coordinate acyltransferase. To date, characterized representatives of short chain fatty acid kinases exhibit relatively narrow substrate specificity. In this work, biochemical characterization of a predicted acetate kinase from Rhodobacter sphaeroides reveals a novel enzyme with broad substrate specificity for primary fatty acids of varying lengths (C2--C8).
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Affiliation(s)
- Maxwell J Bachochin
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, 900 Wood Rd, Kenosha, WI, 53141-2000, USA
| | - Michelle Van Allen
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, 900 Wood Rd, Kenosha, WI, 53141-2000, USA
| | - Robert D Barber
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, 900 Wood Rd, Kenosha, WI, 53141-2000, USA.
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Bachochin MJ, Venegas JC, Singh G, Zhang L, Barber RD. Characterization of a butyrate kinase from Desulfovibrio vulgaris str. Hildenborough. FEMS Microbiol Lett 2020; 367:5804727. [PMID: 32166312 DOI: 10.1093/femsle/fnaa047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 03/10/2020] [Indexed: 11/13/2022] Open
Abstract
Short and branched chain fatty acid kinases participate in both bacterial anabolic and catabolic processes, including fermentation, through the reversible, ATP-dependent synthesis of acyl phosphates. This study reports biochemical properties of a predicted butyrate kinase from Desulfovibrio vulgaris str. Hildenborough (DvBuk) expressed heterologously and purified from Escherichia coli. Gel filtration chromatography indicates purified DvBuk is active as a dimer. The optimum temperature and pH for DvBuk activity is 44°C and 7.5, respectively. The enzyme displays enhanced thermal stability in the presence of substrates as observed for similar enzymes. Measurement of kcat and KM for various substrates reveals DvBuk exhibits the highest catalytic efficiencies for butyrate, valerate and isobutyrate. In particular, these measurements reveal this enzyme's apparent high affinity for C4 fatty acids relative to other butyrate kinases. These results have implications on structure and function relationships within the ASKHA superfamily of phosphotransferases, particularly regarding the acyl binding pocket, as well as potential physiological roles for this enzyme in Desulfovibrio vulgaris str. Hildenborough.
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Affiliation(s)
- Maxwell J Bachochin
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, Room 355 Greenquist Hall; 900 Wood Rd., Kenosha, WI 53141-2000, USA
| | - Jessica Castillo Venegas
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, Room 355 Greenquist Hall; 900 Wood Rd., Kenosha, WI 53141-2000, USA
| | - Gundeep Singh
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, Room 355 Greenquist Hall; 900 Wood Rd., Kenosha, WI 53141-2000, USA
| | - Liyang Zhang
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, Room 355 Greenquist Hall; 900 Wood Rd., Kenosha, WI 53141-2000, USA
| | - Robert D Barber
- Department of Biological Sciences, College of Natural and Health Sciences, University of Wisconsin-Parkside, Room 355 Greenquist Hall; 900 Wood Rd., Kenosha, WI 53141-2000, USA
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7
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Wu C, McCune TS. Implementation of research on potential drug target cloning and characterization in a biochemistry laboratory. BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION : A BIMONTHLY PUBLICATION OF THE INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2020; 48:108-117. [PMID: 31782881 DOI: 10.1002/bmb.21319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 10/21/2019] [Accepted: 11/15/2019] [Indexed: 06/10/2023]
Abstract
An approach for incorporating preliminary drug discovery research into a biochemistry laboratory is described. During a total of 42 hr (one 3-hr laboratory section a week for 14 weeks), students were exposed to bioinformatics; molecular cloning; protein expression, purification, and characterization; and enzymatic kinetic assays. This research-oriented laboratory not only includes the standard elements of common undergraduate biochemistry laboratory manuals but also emphasizes the logical connections among biochemistry laboratory techniques. Moreover, this approach exposed students to laboratory research and the concept of drug discovery.
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Affiliation(s)
- Chun Wu
- Division of Natural Sciences, Mount Marty College, Yankton, South Dakota
| | - Tyler S McCune
- Division of Natural Sciences, Mount Marty College, Yankton, South Dakota
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Yoshida Y, Sato M, Nonaka T, Hasegawa Y, Kezuka Y. Characterization of the phosphotransacetylase-acetate kinase pathway for ATP production in Porphyromonas gingivalis. J Oral Microbiol 2019; 11:1588086. [PMID: 31007866 PMCID: PMC6461089 DOI: 10.1080/20002297.2019.1588086] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 02/18/2019] [Accepted: 02/25/2019] [Indexed: 12/19/2022] Open
Abstract
Acetyl phosphate (AcP) is generally produced from acetyl coenzyme A by phosphotransacetylase (Pta), and subsequent reaction with ADP, catalyzed by acetate kinase (Ack), produces ATP. The mechanism of ATP production in Porphyromonas gingivalis is poorly understood. The aim of this study was to explore the molecular basis of the Pta-Ack pathway in this microorganism. Pta and Ack from P. gingivalis ATCC 33277 were enzymatically and structurally characterized. Structural and mutational analyses suggest that Pta is a dimer with two substrate-binding sites in each subunit. Ack is also dimeric, with a catalytic cleft in each subunit, and structural analysis indicates a dramatic domain motion that opens and closes the cleft during catalysis. ATP formation by Ack proceeds via a sequential mechanism. Reverse transcription-PCR analysis demonstrated that the pta (PGN_1179) and ack (PGN_1178) genes, tandemly located in the genome, are cotranscribed as an operon. Inactivation of pta or ack in P. gingivalis by homologous recombination was successful only when the inactivated gene was expressed in trans. Therefore, both pta and ack genes are essential for this microorganism. Insights into the Pta-Ack pathway reported herein would be helpful to understand the energy acquisition in P. gingivalis.
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Affiliation(s)
- Yasuo Yoshida
- Department of Microbiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan
| | - Mitsunari Sato
- Department of Microbiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan
| | - Takamasa Nonaka
- Division of Structural Biology, Department of Pharmaceutical Sciences, School of Pharmacy, Iwate Medical University, Yahaba, Japan
| | - Yoshiaki Hasegawa
- Department of Microbiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan
| | - Yuichiro Kezuka
- Division of Structural Biology, Department of Pharmaceutical Sciences, School of Pharmacy, Iwate Medical University, Yahaba, Japan
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9
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Dang T, Ingram-Smith C. Investigation of pyrophosphate versus ATP substrate selection in the Entamoeba histolytica acetate kinase. Sci Rep 2017; 7:5912. [PMID: 28724909 PMCID: PMC5517563 DOI: 10.1038/s41598-017-06156-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 06/08/2017] [Indexed: 12/21/2022] Open
Abstract
Acetate kinase (ACK; E.C. 2.7.2.1), which catalyzes the interconversion of acetate and acetyl phosphate, is nearly ubiquitous in bacteria but is present only in one genus of archaea and certain eukaryotic microbes. All ACKs utilize ATP/ADP as the phosphoryl donor/acceptor in the respective directions of the reaction (acetate + ATP \documentclass[12pt]{minimal}
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\begin{document}$${\boldsymbol{\leftrightarrows }}$$\end{document}⇆ acetyl phosphate + ADP), with the exception of the Entamoeba histolytica ACK (EhACK) which uses pyrophosphate (PPi)/inorganic phosphate (Pi) (acetyl phosphate + Pi
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\begin{document}$${\boldsymbol{\leftrightarrows }}$$\end{document}⇆ acetate + PPi). Structural analysis and modeling of EhACK indicated steric hindrance by active site residues constricts entry to the adenosine pocket as compared to ATP-utilizing Methanosarcina thermophila ACK (MtACK). Reciprocal alterations were made to enlarge the adenosine pocket of EhACK and reduce that of MtACK. The EhACK variants showed a step-wise increase in ADP and ATP binding but were still unable to use these as substrates, and enzymatic activity with Pi/PPi was negatively impacted. Consistent with this, ATP utilization by MtACK variants was negatively affected but the alterations were not sufficient to convert this enzyme to Pi/PPi utilization. Our results suggest that controlling access to the adenosine pocket can contribute to substrate specificity but is not the sole determinant.
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Affiliation(s)
- Thanh Dang
- Department of Genetics and Biochemistry and the Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC, 29634, USA
| | - Cheryl Ingram-Smith
- Department of Genetics and Biochemistry and the Eukaryotic Pathogens Innovation Center, Clemson University, Clemson, SC, 29634, USA.
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Gonzalez-Gil L, Carballa M, Lema JM. Cometabolic Enzymatic Transformation of Organic Micropollutants under Methanogenic Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:2963-2971. [PMID: 28198617 DOI: 10.1021/acs.est.6b05549] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Anaerobic digestion (AD) has been shown to have the biological potential to decrease concentrations of several organic micropollutants (OMPs) in sewage sludge. However, the mechanisms and factors behind these biotransformations, which are essential for elucidating the possible transformation products and to foster the complete removal of OMPs via operational strategies, remain unclear. Therefore, this study investigated the transformation mechanisms of 20 OMPs during the methanogenic step of AD with a focus on the role of acetate kinase (AK), which is a key enzyme in methane production. The results from lab-scale methanogenic reactors showed that this step accounts for much of the reported OMP biotransformation in AD. Furthermore, enzymatic assays confirmed that AK transforms galaxolide, naproxen, nonylphenol, octylphenol, ibuprofen, diclofenac, bisphenol A, and triclosan. Except for galaxolide, for which further studies are required to refine conclusions, the OMP's chemical structure was a determinant for AK action because only compounds that contain a carboxyl or hydroxyl group and have moderate steric hindrance were enzymatically transformed, likely by phosphorylation. For these seven compounds, this enzymatic mechanism accounts for 10-90% of the measured methanogenic biotransformation, suggesting that other active enzymes of the AD process are also involved in OMP biotransformation.
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Affiliation(s)
- Lorena Gonzalez-Gil
- Department of Chemical Engineering, Institute of Technology, Universidade de Santiago de Compostela , Campus Vida, 15782 Santiago de Compostela, Spain
| | - Marta Carballa
- Department of Chemical Engineering, Institute of Technology, Universidade de Santiago de Compostela , Campus Vida, 15782 Santiago de Compostela, Spain
| | - Juan M Lema
- Department of Chemical Engineering, Institute of Technology, Universidade de Santiago de Compostela , Campus Vida, 15782 Santiago de Compostela, Spain
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11
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Structure of the acetophenone carboxylase core complex: prototype of a new class of ATP-dependent carboxylases/hydrolases. Sci Rep 2017; 7:39674. [PMID: 28054554 PMCID: PMC5214803 DOI: 10.1038/srep39674] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/24/2016] [Indexed: 01/15/2023] Open
Abstract
Degradation of the aromatic ketone acetophenone is initiated by its carboxylation to benzoylacetate catalyzed by acetophenone carboxylase (Apc) in a reaction dependent on the hydrolysis of two ATP to ADP and Pi. Apc is a large protein complex which dissociates during purification into a heterooctameric Apc(αα′βγ)2 core complex of 482 kDa and Apcε of 34 kDa. In this report, we present the X-ray structure of the Apc(αα′βγ)2 core complex from Aromatoleum aromaticum at ca. 3 Å resolution which reveals a unique modular architecture and serves as model of a new enzyme family. Apcβ contains a novel domain fold composed of two β-sheets in a barrel-like arrangement running into a bundle of eight short polyproline (type II)-like helical segments. Apcα and Apcα′ possess ATP binding modules of the ASKHA superfamily integrated into their multidomain structures and presumably operate as ATP-dependent kinases for acetophenone and bicarbonate, respectively. Mechanistic aspects of the novel carboxylation reaction requiring massive structural rearrangements are discussed and criteria for specifically annotating the family members Apc, acetone carboxylase and hydantoinase are defined.
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Narihiro T, Nobu MK, Tamaki H, Kamagata Y, Sekiguchi Y, Liu WT. Comparative Genomics of Syntrophic Branched-Chain Fatty Acid Degrading Bacteria. Microbes Environ 2016; 31:288-92. [PMID: 27431485 PMCID: PMC5017805 DOI: 10.1264/jsme2.me16057] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The syntrophic degradation of branched-chain fatty acids (BCFAs) such as 2-methylbutyrate and isobutyrate is an essential step in the production of methane from proteins/amino acids in anaerobic ecosystems. While a few syntrophic BCFA-degrading bacteria have been isolated, their metabolic pathways in BCFA and short-chain fatty acid (SCFA) degradation as well as energy conservation systems remain unclear. In an attempt to identify these pathways, we herein performed comparative genomics of three syntrophic bacteria: 2-methylbutyrate-degrading “Syntrophomonas wolfei subsp. methylbutyratica” strain JCM 14075T (=4J5T), isobutyrate-degrading Syntrophothermus lipocalidus strain TGB-C1T, and non-BCFA-metabolizing S. wolfei subsp. wolfei strain GöttingenT. We demonstrated that 4J5 and TGB-C1 both encode multiple genes/gene clusters involved in β-oxidation, as observed in the Göttingen genome, which has multiple copies of genes associated with butyrate degradation. The 4J5 genome possesses phylogenetically distinct β-oxidation genes, which may be involved in 2-methylbutyrate degradation. In addition, these Syntrophomonadaceae strains harbor various hydrogen/formate generation systems (i.e., electron-bifurcating hydrogenase, formate dehydrogenase, and membrane-bound hydrogenase) and energy-conserving electron transport systems, including electron transfer flavoprotein (ETF)-linked acyl-CoA dehydrogenase, ETF-linked iron-sulfur binding reductase, ETF dehydrogenase (FixABCX), and flavin oxidoreductase-heterodisulfide reductase (Flox-Hdr). Unexpectedly, the TGB-C1 genome encodes a nitrogenase complex, which may function as an alternative H2 generation mechanism. These results suggest that the BCFA-degrading syntrophic strains 4J5 and TGB-C1 possess specific β-oxidation-related enzymes for BCFA oxidation as well as appropriate energy conservation systems to perform thermodynamically unfavorable syntrophic metabolism.
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Affiliation(s)
- Takashi Narihiro
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
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Moore TC, Escalante-Semerena JC. The EutQ and EutP proteins are novel acetate kinases involved in ethanolamine catabolism: physiological implications for the function of the ethanolamine metabolosome in Salmonella enterica. Mol Microbiol 2015; 99:497-511. [PMID: 26448059 DOI: 10.1111/mmi.13243] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/05/2015] [Indexed: 11/29/2022]
Abstract
Salmonella enterica catabolizes ethanolamine inside a compartment known as the metabolosome. The ethanolamine utilization (eut) operon of this bacterium encodes all functions needed for the assembly and function of this structure. To date, the roles of EutQ and EutP were not known. Herein we show that both proteins have acetate kinase activity and that EutQ is required during anoxic growth of S. enterica on ethanolamine and tetrathionate. EutP and EutQ-dependent ATP synthesis occurred when enzymes were incubated with ADP, Mg(II) ions and acetyl-phosphate. EutQ and EutP also synthesized acetyl-phosphate from ATP and acetate. Although EutP had acetate kinase activity, ΔeutP strains lacked discernible phenotypes under the conditions where ΔeutQ strains displayed clear phenotypes. The kinetic parameters indicate that EutP is a faster enzyme than EutQ. Our evidence supports the conclusion that EutQ and EutP represent novel classes of acetate kinases. We propose that EutQ is necessary to drive flux through the pathway under physiological conditions, preventing a buildup of acetaldehyde. We also suggest that ATP generated by these enzymes may be used as a substrate for EutT, the ATP-dependent corrinoid adenosyltransferase and for the EutA ethanolamine ammonia-lyase reactivase.
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Affiliation(s)
- Theodore C Moore
- Department of Microbiology, University of Georgia, 120 Cedar Street, Athens, GA, 30602, USA
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14
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Rozova ON, Khmelenina VN, Gavletdinova JZ, Mustakhimov II, Trotsenko YA. Acetate kinase-an enzyme of the postulated phosphoketolase pathway in Methylomicrobium alcaliphilum 20Z. Antonie van Leeuwenhoek 2015; 108:965-74. [PMID: 26275877 DOI: 10.1007/s10482-015-0549-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 07/24/2015] [Indexed: 01/10/2023]
Abstract
Recombinant acetate kinase (AcK) was obtained from the aerobic haloalkalitolerant methanotroph Methylomicrobium alcaliphilum 20Z by heterologous expression in Escherichia coli and purification by affinity chromatography. The substrate specificity, the kinetics and oligomeric state of the His6-tagged AcK were determined. The M. alcaliphilum AcK (2 × 45 kDa) catalyzed the reversible phosphorylation of acetate into acetyl phosphate and exhibited a dependence on Mg(2+) or Mn(2+) ions and strong specificity to ATP/ADP. The enzyme showed the maximal activity and high stability at 70 °C. AcK was 20-fold more active in the reaction of acetate synthesis compared to acetate phosphorylation and had a higher affinity to acetyl phosphate (K m 0.11 mM) than to acetate (K m 5.6 mM). The k cat /K m ratios indicated that the enzyme had a remarkably high catalytic efficiency for acetate and ATP formation (k cat/K m = 1.7 × 10(6)) compared to acetate phosphorylation (k cat/K m = 2.5 × 10(3)). The ack gene of M. alcaliphilum 20Z was shown to be co-transcribed with the xfp gene encoding putative phosphoketolase. The Blast analysis revealed the ack and xfp genes in most genomes of the sequenced aerobic methanotrophs, as well as methylotrophic bacteria not growing on methane. The distribution and metabolic role of the postulated phosphoketolase shunted glycolytic pathway in aerobic C1-utilizing bacteria is discussed.
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Affiliation(s)
- Olga N Rozova
- Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, Prospect Nauki 5, Pushchino, 142290, Russia,
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15
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Ferry JG. Acetate Metabolism in Anaerobes from the Domain Archaea. Life (Basel) 2015; 5:1454-71. [PMID: 26068860 PMCID: PMC4500148 DOI: 10.3390/life5021454] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 06/01/2015] [Indexed: 01/26/2023] Open
Abstract
Acetate and acetyl-CoA play fundamental roles in all of biology, including anaerobic prokaryotes from the domains Bacteria and Archaea, which compose an estimated quarter of all living protoplasm in Earth's biosphere. Anaerobes from the domain Archaea contribute to the global carbon cycle by metabolizing acetate as a growth substrate or product. They are components of anaerobic microbial food chains converting complex organic matter to methane, and many fix CO2 into cell material via synthesis of acetyl-CoA. They are found in a diversity of ecological habitats ranging from the digestive tracts of insects to deep-sea hydrothermal vents, and synthesize a plethora of novel enzymes with biotechnological potential. Ecological investigations suggest that still more acetate-metabolizing species with novel properties await discovery.
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Affiliation(s)
- James G Ferry
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
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16
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Müller B, Manzoor S, Niazi A, Bongcam-Rudloff E, Schnürer A. Genome-guided analysis of physiological capacities of Tepidanaerobacter acetatoxydans provides insights into environmental adaptations and syntrophic acetate oxidation. PLoS One 2015; 10:e0121237. [PMID: 25811859 PMCID: PMC4374699 DOI: 10.1371/journal.pone.0121237] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 01/30/2015] [Indexed: 11/21/2022] Open
Abstract
This paper describes the genome-based analysis of Tepidanaerobacter acetatoxydans strain Re1, a syntrophic acetate-oxidising bacterium (SAOB). Principal issues such as environmental adaptations, metabolic capacities, and energy conserving systems have been investigated and the potential consequences for syntrophic acetate oxidation discussed. Briefly, in pure culture, T. acetatoxydans grows with different organic compounds and produces acetate as the main product. In a syntrophic consortium with a hydrogenotrophic methanogen, it can also reverse its metabolism and instead convert acetate to formate/H2 and CO2. It can only proceed if the product formed is continuously removed. This process generates a very small amount of energy that is scarcely enough for growth, which makes this particular syntrophy of special interest. As a crucial member of the biogas-producing community in ammonium-rich engineered AD processes, genomic features conferring ammonium resistance, bacterial defense, oxygen and temperature tolerance were found, as well as attributes related to biofilm formation and flocculation. It is likely that T. acetatoxydans can form an electrochemical gradient by putative electron-bifurcating Rnf complex and [Fe-Fe] hydrogenases, as observed in other acetogens. However, genomic deficiencies related to acetogenic metabolism and anaerobic respiration were discovered, such as the lack of formate dehydrogenase and F1F0 ATP synthase. This has potential consequences for the metabolic pathways used under SAO and non-SAO conditions. The two complete sets of bacteriophage genomes, which were found to be encoded in the genome, are also worthy of mention.
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Affiliation(s)
- Bettina Müller
- Department of Microbiology, Swedish University of Agricultural Sciences, BioCenter, Uppsala, Sweden
- * E-mail:
| | - Shahid Manzoor
- Department of Animal Breeding and Genetics Science, Swedish University of Agricultural Science, SLU-Global Bioinformatics Centre, Uppsala, Sweden
- University of the Punjab, Lahore, Pakistan
| | - Adnan Niazi
- Department of Animal Breeding and Genetics Science, Swedish University of Agricultural Science, SLU-Global Bioinformatics Centre, Uppsala, Sweden
| | - Erik Bongcam-Rudloff
- Department of Animal Breeding and Genetics Science, Swedish University of Agricultural Science, SLU-Global Bioinformatics Centre, Uppsala, Sweden
| | - Anna Schnürer
- Department of Microbiology, Swedish University of Agricultural Sciences, BioCenter, Uppsala, Sweden
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17
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Ingram-Smith C, Wharton J, Reinholz C, Doucet T, Hesler R, Smith K. The Role of Active Site Residues in ATP Binding and Catalysis in the Methanosarcina thermophila Acetate Kinase. Life (Basel) 2015; 5:861-71. [PMID: 25775277 PMCID: PMC4390882 DOI: 10.3390/life5010861] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/02/2015] [Accepted: 03/04/2015] [Indexed: 11/16/2022] Open
Abstract
Acetate kinase (ACK), which catalyzes the reversible phosphorylation of acetate by ATP, is a member of the acetate and sugar kinase/heat shock cognate/actin (ASKHA) superfamily. ASKHA family members share a common core fold that includes an ATPase domain with five structural motifs. The PHOSPHATE1 motif has previously been shown to be important for catalysis. We have investigated the role of two of these motifs in the Methanosarcina thermophila ACK (MtACK) and have shown that residues projecting into the ACK active site from the PHOSPHATE2 and ADENOSINE loops and a third highly conserved loop designated here as LOOP3 play key roles in nucleotide triphosphate (NTP) selection and utilization. Alteration of Asn211 of PHOSPHATE2, Gly239 of LOOP3, and Gly331 of ADENOSINE greatly reduced catalysis. In particular, Gly331, which is highly conserved throughout the ASKHA superfamily, has the greatest effect on substrate selection. Alteration at this site strongly skewed MtACK toward utilization of purines over pyrimidines, unlike the wild type enzyme that shows broad NTP utilization. Further investigation into differences between the ATPase domain in MtACK and other acetate kinases that show different substrate preferences will provide us with a better understanding of the diversity of phosphoryl donor selection in this enzyme family.
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Affiliation(s)
- Cheryl Ingram-Smith
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
| | - Jeffrey Wharton
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
| | - Christian Reinholz
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
| | - Tara Doucet
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
| | - Rachel Hesler
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
| | - Kerry Smith
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634, USA.
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18
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Yang W, Catalanotti C, D'Adamo S, Wittkopp TM, Ingram-Smith CJ, Mackinder L, Miller TE, Heuberger AL, Peers G, Smith KS, Jonikas MC, Grossman AR, Posewitz MC. Alternative acetate production pathways in Chlamydomonas reinhardtii during dark anoxia and the dominant role of chloroplasts in fermentative acetate production. THE PLANT CELL 2014; 26:4499-518. [PMID: 25381350 PMCID: PMC4277214 DOI: 10.1105/tpc.114.129965] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 07/15/2014] [Accepted: 10/15/2014] [Indexed: 05/18/2023]
Abstract
Chlamydomonas reinhardtii insertion mutants disrupted for genes encoding acetate kinases (EC 2.7.2.1) (ACK1 and ACK2) and a phosphate acetyltransferase (EC 2.3.1.8) (PAT2, but not PAT1) were isolated to characterize fermentative acetate production. ACK1 and PAT2 were localized to chloroplasts, while ACK2 and PAT1 were shown to be in mitochondria. Characterization of the mutants showed that PAT2 and ACK1 activity in chloroplasts plays a dominant role (relative to ACK2 and PAT1 in mitochondria) in producing acetate under dark, anoxic conditions and, surprisingly, also suggested that Chlamydomonas has other pathways that generate acetate in the absence of ACK activity. We identified a number of proteins associated with alternative pathways for acetate production that are encoded on the Chlamydomonas genome. Furthermore, we observed that only modest alterations in the accumulation of fermentative products occurred in the ack1, ack2, and ack1 ack2 mutants, which contrasts with the substantial metabolite alterations described in strains devoid of other key fermentation enzymes.
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Affiliation(s)
- Wenqiang Yang
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305
| | - Claudia Catalanotti
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305
| | - Sarah D'Adamo
- Colorado School of Mines, Department of Chemistry and Geochemistry, Golden, Colorado 80401
| | - Tyler M Wittkopp
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305 Stanford University, Department of Biology, Stanford, California 94305
| | - Cheryl J Ingram-Smith
- Clemson University, Department of Genetics and Biochemistry, Clemson, South Carolina 29634
| | - Luke Mackinder
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305
| | - Tarryn E Miller
- Colorado School of Mines, Department of Chemistry and Geochemistry, Golden, Colorado 80401
| | - Adam L Heuberger
- Colorado State University, Proteomics and Metabolomics Facility, Fort Collins, Colorado 80523
| | - Graham Peers
- Colorado State University, Department of Biology, Fort Collins, Colorado 80523
| | - Kerry S Smith
- Clemson University, Department of Genetics and Biochemistry, Clemson, South Carolina 29634
| | - Martin C Jonikas
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305
| | - Arthur R Grossman
- Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305
| | - Matthew C Posewitz
- Colorado School of Mines, Department of Chemistry and Geochemistry, Golden, Colorado 80401
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19
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Welte C, Kröninger L, Deppenmeier U. Experimental evidence of an acetate transporter protein and characterization of acetate activation in aceticlastic methanogenesis of Methanosarcina mazei. FEMS Microbiol Lett 2014; 359:147-53. [PMID: 25088360 DOI: 10.1111/1574-6968.12550] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 06/12/2014] [Accepted: 07/28/2014] [Indexed: 11/29/2022] Open
Abstract
Aceticlastic methanogens metabolize acetate to methane and carbon dioxide. The central metabolism and the electron transport chains of these organisms have already been investigated. However, no particular attention has been paid to the mechanism by which acetate enters the archaeal cell. In our study we investigated Methanosarcina mazei acetate kinase (Ack) and the acetate uptake reaction. At a concentration of 2 mM acetate, the Ack activity in cell extract of M. mazei was not limiting for the methane formation rate. Instead, the methanogenesis rate was controlled by the substrate concentration and increased 10-fold at 10 mM acetate. Subsequently, we analyzed the involvement of the putative acetate permease MM_0903 using a corresponding deletion mutant. At 2 mM acetate, only 25% of the wild-type methane formation rate was measured in the mutant. This indicated that the supply of acetate to Ack was limiting the rate of methane formation. Moreover, the mutant revealed an increased acetate kinase activity compared with the wild type. These results show for the first time that an acetate transporter is involved in aceticlastic methanogenesis and may be an important factor in the acetate threshold concentration for methanogenesis of Methanosarcina spp.
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Affiliation(s)
- Cornelia Welte
- Institute for Microbiology & Biotechnology, University of Bonn, Bonn, Germany; Department of Microbiology, Radboud University Nijmegen, Nijmegen, The Netherlands
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20
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Yoshioka A, Murata K, Kawai S. Structural and mutational analysis of amino acid residues involved in ATP specificity of Escherichia coli acetate kinase. J Biosci Bioeng 2014; 118:502-7. [PMID: 24856051 DOI: 10.1016/j.jbiosc.2014.04.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 04/21/2014] [Accepted: 04/21/2014] [Indexed: 11/30/2022]
Abstract
Acetate kinase (AK) generally utilizes ATP as a phosphoryl donor, but AK from Entamoeba histolytica (PPi-ehiAK) uses pyrophosphate (PPi), not ATP, and is PPi-specific. The determinants of the phosphoryl donor specificity are unknown. Here, we inferred 5 candidate amino acid residues associated with this specificity, based on structural information. Each candidate residue in Escherichia coli ATP-specific AK (ATP-ecoAK), which is unable to use PPi, was substituted with the respective PPi-ehiAK amino acid residue. Each variant ATP-ecoAK had an increased Km for ATP, indicating that the 5 residues are the determinants for the specificity to ATP in ATP-ecoAK. Moreover, Asn-337 of ATP-ecoAK was shown to be particularly significant for the specificity to ATP. The 5 residues are highly conserved in 2625 PPi-ehiAK homologs, implying that almost all organisms have ATP-dependent, rather than PPi-dependent, AK.
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Affiliation(s)
- Aya Yoshioka
- Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Kousaku Murata
- Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Shigeyuki Kawai
- Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
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21
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Cold Adaptation: Structural and Functional Characterizations of Psychrophilic and Mesophilic Acetate Kinase. Protein J 2014; 33:313-22. [DOI: 10.1007/s10930-014-9562-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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22
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23
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Towards a computational model of a methane producing archaeum. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2014; 2014:898453. [PMID: 24729742 PMCID: PMC3960522 DOI: 10.1155/2014/898453] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 12/18/2013] [Indexed: 11/17/2022]
Abstract
Progress towards a complete model of the methanogenic archaeum Methanosarcina acetivorans is reported. We characterized size distribution of the cells using differential interference contrast microscopy, finding them to be ellipsoidal with mean length and width of 2.9 μm and 2.3 μm, respectively, when grown on methanol and 30% smaller when grown on acetate. We used the single molecule pull down (SiMPull) technique to measure average copy number of the Mcr complex and ribosomes. A kinetic model for the methanogenesis pathways based on biochemical studies and recent metabolic reconstructions for several related methanogens is presented. In this model, 26 reactions in the methanogenesis pathways are coupled to a cell mass production reaction that updates enzyme concentrations. RNA expression data (RNA-seq) measured for cell cultures grown on acetate and methanol is used to estimate relative protein production per mole of ATP consumed. The model captures the experimentally observed methane production rates for cells growing on methanol and is most sensitive to the number of methyl-coenzyme-M reductase (Mcr) and methyl-tetrahydromethanopterin:coenzyme-M methyltransferase (Mtr) proteins. A draft transcriptional regulation network based on known interactions is proposed which we intend to integrate with the kinetic model to allow dynamic regulation.
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24
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Similar connotation in chronic hepatitis B and nonalcoholic Fatty liver patients with dampness-heat syndrome. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:793820. [PMID: 23690853 PMCID: PMC3638589 DOI: 10.1155/2013/793820] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 03/02/2013] [Accepted: 03/04/2013] [Indexed: 11/30/2022]
Abstract
The phenomenon that the same syndrome turns up in different diseases appears in the sight of people around the world, which raises the thought for possibility of “Same Treatment for Different Diseases.” Actually, treatment based on ZHENG classification in Traditional Chinese Medicine could bring revelation for the former finding. The dampness-heat syndrome in chronic hepatitis B and nonalcoholic fatty liver is regarded as the breakthrough point. We discussed the molecular mechanism of similar connotation that exists in chronic hepatitis B and nonalcoholic fatty liver by metabonomics to give the modern understanding of dampness-heat syndrome. Both urine and serum metabolic profiling revealed that obvious differences existed between dampness-heat syndrome and non-dampness-heat syndrome but the commonality was proved to appear in chronic hepatitis B and nonalcoholic fatty liver patients with dampness-heat syndrome. Furthermore, disorder of body fluid metabolism, decline in digestive capacity, and imbalance of intestinal flora were found to be the new guiding for treatment, with the hope to provide the basis for Chinese personalized medicine.
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25
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Miller CL, Karna SLR, Seshu J. Borrelia host adaptation Regulator (BadR) regulates rpoS to modulate host adaptation and virulence factors in Borrelia burgdorferi. Mol Microbiol 2013; 88:105-24. [PMID: 23387366 DOI: 10.1111/mmi.12171] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2013] [Indexed: 11/27/2022]
Abstract
The RpoS transcription factor of Borrelia burgdorferi is a 'gatekeeper' because it activates genes required for spirochaetes to transition from tick to vertebrate hosts. However, it remains unknown how RpoS becomes repressed to allow the spirochaetes to transition back from the vertebrate host to the tick vector. Here we show that a putative carbohydrate-responsive regulatory protein, designated BadR (Borrelia host adaptation Regulator), is a transcriptional repressor of rpoS. BadR levels are elevated in B. burgdorferi cultures grown under in vitro conditions mimicking unfed-ticks and badR-deficient strains are defective for growth under these same conditions. Microarray and immunoblot analyses of badR-deficient strains showed upregulation of rpoS and other factors important for virulence in vertebrate hosts, as well as downregulation of putative tick-specific determinants (e.g. linear plasmid 28-4 genes). DNA-binding assays revealed BadR binds to upstream regions of rpoS. Site-directed mutations in BadR and the presence of phosphorylated sugars affected BadR's binding to the rpoS promoters. badR-deficient B. burgdorferi were unable to colonize mice. Several putative tick-specific targets have been identified. Our study identified a novel regulator, BadR, and provides a link between nutritional environmental cues utilized by spirochaetes to adaptation to disparate conditions found in the tick and vertebrate hosts.
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Affiliation(s)
- Christine L Miller
- South Texas Center for Emerging Infectious Diseases, Center for Excellence in Infection Genomics and Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, USA
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26
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Lira-Silva E, Santiago-Martínez MG, Hernández-Juárez V, García-Contreras R, Moreno-Sánchez R, Jasso-Chávez R. Activation of methanogenesis by cadmium in the marine archaeon Methanosarcina acetivorans. PLoS One 2012; 7:e48779. [PMID: 23152802 PMCID: PMC3495967 DOI: 10.1371/journal.pone.0048779] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 10/01/2012] [Indexed: 12/01/2022] Open
Abstract
Methanosarcina acetivorans was cultured in the presence of CdCl2 to determine the metal effect on cell growth and biogas production. With methanol as substrate, cell growth and methane synthesis were not altered by cadmium, whereas with acetate, cadmium slightly increased both, growth and methane rate synthesis. In cultures metabolically active, incubations for short-term (minutes) with 10 µM total cadmium increased the methanogenesis rate by 6 and 9 folds in methanol- and acetate-grown cells, respectively. Cobalt and zinc but not copper or iron also activated the methane production rate. Methanogenic carbonic anhydrase and acetate kinase were directly activated by cadmium. Indeed, cells cultured in 100 µM total cadmium removed 41–69% of the heavy metal from the culture and accumulated 231–539 nmol Cd/mg cell protein. This is the first report showing that (i) Cd2+ has an activating effect on methanogenesis, a biotechnological relevant process in the bio-fuels field; and (ii) a methanogenic archaea is able to remove a heavy metal from aquatic environments.
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Affiliation(s)
- Elizabeth Lira-Silva
- Departamento de Bioquímica, Instituto Nacional de Cardiología, Tlalpan, México D.F., México
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27
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Novel pyrophosphate-forming acetate kinase from the protist Entamoeba histolytica. EUKARYOTIC CELL 2012; 11:1249-56. [PMID: 22903977 DOI: 10.1128/ec.00169-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Acetate kinase (ACK) catalyzes the reversible synthesis of acetyl phosphate by transfer of the γ-phosphate of ATP to acetate. Here we report the first biochemical and kinetic characterization of a eukaryotic ACK, that from the protist Entamoeba histolytica. Our characterization revealed that this protist ACK is the only known member of the ASKHA structural superfamily, which includes acetate kinase, hexokinase, and other sugar kinases, to utilize inorganic pyrophosphate (PP(i))/inorganic phosphate (P(i)) as the sole phosphoryl donor/acceptor. Detection of ACK activity in E. histolytica cell extracts in the direction of acetate/PP(i) formation but not in the direction of acetyl phosphate/P(i) formation suggests that the physiological direction of the reaction is toward acetate/PP(i) production. Kinetic parameters determined for each direction of the reaction are consistent with this observation. The E. histolytica PP(i)-forming ACK follows a sequential mechanism, supporting a direct in-line phosphoryl transfer mechanism as previously reported for the well-characterized Methanosarcina thermophila ATP-dependent ACK. Characterizations of enzyme variants altered in the putative acetate/acetyl phosphate binding pocket suggested that acetyl phosphate binding is not mediated solely through a hydrophobic interaction but also through the phosphoryl group, as for the M. thermophila ACK. However, there are key differences in the roles of certain active site residues between the two enzymes. The absence of known ACK partner enzymes raises the possibility that ACK is part of a novel pathway in Entamoeba.
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28
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Fluorescence Studies on the Stability, Flexibility and Substrate-Induced Conformational Changes of Acetate Kinases from Psychrophilic and Mesophilic Bacteria. Protein J 2012; 31:337-44. [DOI: 10.1007/s10930-012-9408-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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29
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Fowler ML, Ingram-Smith CJ, Smith KS. Direct detection of the acetate-forming activity of the enzyme acetate kinase. J Vis Exp 2011:3474. [PMID: 22214984 DOI: 10.3791/3474] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Acetate kinase, a member of the acetate and sugar kinase-Hsp70-actin (ASKHA) enzyme superfamily, is responsible for the reversible phosphorylation of acetate to acetyl phosphate utilizing ATP as a substrate. Acetate kinases are ubiquitous in the Bacteria, found in one genus of Archaea, and are also present in microbes of the Eukarya. The most well characterized acetate kinase is that from the methane-producing archaeon Methanosarcina thermophila. An acetate kinase which can only utilize PP(i) but not ATP in the acetyl phosphate-forming direction has been isolated from Entamoeba histolytica, the causative agent of amoebic dysentery, and has thus far only been found in this genus. In the direction of acetyl phosphate formation, acetate kinase activity is typically measured using the hydroxamate assay, first described by Lipmann, a coupled assay in which conversion of ATP to ADP is coupled to oxidation of NADH to NAD(+) by the enzymes pyruvate kinase and lactate dehydrogenase, or an assay measuring release of inorganic phosphate after reaction of the acetyl phosphate product with hydroxylamine. Activity in the opposite, acetate-forming direction is measured by coupling ATP formation from ADP to the reduction of NADP(+) to NADPH by the enzymes hexokinase and glucose 6-phosphate dehydrogenase. Here we describe a method for the detection of acetate kinase activity in the direction of acetate formation that does not require coupling enzymes, but is instead based on direct determination of acetyl phosphate consumption. After the enzymatic reaction, remaining acetyl phosphate is converted to a ferric hydroxamate complex that can be measured spectrophotometrically, as for the hydroxamate assay. Thus, unlike the standard coupled assay for this direction that is dependent on the production of ATP from ADP, this direct assay can be used for acetate kinases that produce ATP or PP(i).
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30
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Abstract
Most of the methane produced in nature derives from the methyl group of acetate, the major end product of anaerobes decomposing complex plant material. The acetate is derived from the metabolic intermediate acetyl-CoA via the combined activities of phosphotransacetylase and acetate kinase. In Methanosarcina species, the enzymes function in the reverse direction to activate acetate to acetyl-CoA prior to cleavage into a methyl and carbonyl group of which the latter is oxidized providing electrons for reduction of the former to methane. Thus, phosphotransacetylase and acetate kinase have a central role in the conversion of complex organic matter to methane by anaerobic microbial food chains. Both enzymes have been purified from Methanosarcina thermophila and characterized. Both enzymes from M. thermophila have also been produced in Escherichia coli permitting crystal structures and amino acid variants, the kinetic and biochemical studies of which have lead to proposals for catalytic mechanisms. The high identity of both enzymes to paralogs in the domain Bacteria suggests ancient origins and common mechanisms.
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Affiliation(s)
- James G Ferry
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania, USA
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31
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Structural correlations of activity of Clostridium acetobutylicum ATCC 824 butyrate kinase isozymes. Enzyme Microb Technol 2010. [DOI: 10.1016/j.enzmictec.2009.10.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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32
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Ragsdale SW, Pierce E. Acetogenesis and the Wood-Ljungdahl pathway of CO(2) fixation. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1784:1873-98. [PMID: 18801467 PMCID: PMC2646786 DOI: 10.1016/j.bbapap.2008.08.012] [Citation(s) in RCA: 706] [Impact Index Per Article: 44.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 08/12/2008] [Accepted: 08/13/2008] [Indexed: 01/04/2023]
Abstract
Conceptually, the simplest way to synthesize an organic molecule is to construct it one carbon at a time. The Wood-Ljungdahl pathway of CO(2) fixation involves this type of stepwise process. The biochemical events that underlie the condensation of two one-carbon units to form the two-carbon compound, acetate, have intrigued chemists, biochemists, and microbiologists for many decades. We begin this review with a description of the biology of acetogenesis. Then, we provide a short history of the important discoveries that have led to the identification of the key components and steps of this usual mechanism of CO and CO(2) fixation. In this historical perspective, we have included reflections that hopefully will sketch the landscape of the controversies, hypotheses, and opinions that led to the key experiments and discoveries. We then describe the properties of the genes and enzymes involved in the pathway and conclude with a section describing some major questions that remain unanswered.
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Affiliation(s)
- Stephen W Ragsdale
- Department of Biological Chemistry, MSRB III, 5301, 1150 W. Medical Center Drive, University of Michigan, Ann Arbor, MI 48109-0606, USA.
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33
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Abstract
The biochemistry of acetogenesis is reviewed. The microbes that catalyze the reactions that are central to acetogenesis are described and the focus is on the enzymology of the process. These microbes play a key role in the global carbon cycle, producing over 10 trillion kilograms of acetic acid annually. Acetogens have the ability to anaerobically convert carbon dioxide and CO into acetyl-CoA by the Wood-Ljungdahl pathway, which is linked to energy conservation. They also can convert the six carbons of glucose stoichiometrically into 3 mol of acetate using this pathway. Acetogens and other anaerobic microbes (e.g., sulfate reducers and methanogens) use the Wood-Ljungdahl pathway for cell carbon synthesis. Important enzymes in this pathway that are covered in this review are pyruvate ferredoxin oxidoreductase, CO dehydrogenase/acetyl-CoA synthase, a corrinoid iron-sulfur protein, a methyltransferase, and the enzymes involved in the conversion of carbon dioxide to methyl-tetrahydrofolate.
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Affiliation(s)
- Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.
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34
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Abstract
The anaerobic conversion of complex organic matter to CH(4) is an essential link in the global carbon cycle. In freshwater anaerobic environments, the organic matter is decomposed to CH(4) and CO(2) by a microbial food chain that terminates with methanogens that produce methane primarily by reduction of the methyl group of acetate and also reduction of CO(2). The process also occurs in marine environments, particularly those receiving large loads of organic matter, such as coastal sediments. The great majority of research on methanogens has focused on marine and freshwater CO(2)-reducing species, and freshwater acetate-utilizing species. Recent molecular, biochemical, bioinformatic, proteomic, and microarray analyses of the marine isolate Methanosarcina acetivorans has revealed that the pathway for acetate conversion to methane differs significantly from that in freshwater methanogens. Similar experimental approaches have also revealed striking contrasts with freshwater species for the pathway of CO-dependent CO(2) reduction to methane by M. acetivorans. The differences in both pathways reflect an adaptation by M. acetivorans to the marine environment.
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Affiliation(s)
- James G Ferry
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
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35
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Mukhopadhyay S, Hasson MS, Sanders DA. A continuous assay of acetate kinase activity: measurement of inorganic phosphate release generated by hydroxylaminolysis of acetyl phosphate. Bioorg Chem 2008; 36:65-9. [PMID: 18294673 PMCID: PMC2376208 DOI: 10.1016/j.bioorg.2007.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 12/18/2007] [Accepted: 12/27/2007] [Indexed: 11/22/2022]
Abstract
Acetate kinase, a member of the ASKHA (Acetate and Sugar Kinases, Hsp70, Actin) phosphotransferase superfamily is a central enzyme in prokaryotic carbon and energy metabolism. Recently extensive structural and biochemical studies of acetate kinase and related carboxylate kinases have been conducted. Analysis of the kinetic properties of wild-type and mutant enzymes has been impeded by the nature of the current assays for acetate kinase activity. These assays have the disadvantages of being either discontinuous or insensitive or of utilizing compounds that interfere with activity measurements. We have developed a novel continuous assay that depends on the purine nucleoside phosphorylase-based spectroscopic measurement of the inorganic phosphate generated by hydroxylaminolysis of one of the products of the acetate kinase reaction, acetyl phosphate. This assay has enabled a determination of the kinetic parameters of the Thermotoga maritima acetate kinase that indicates a lower K(m) for acetate than previously published.
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Affiliation(s)
- Soma Mukhopadhyay
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
| | | | - David A. Sanders
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907
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36
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Simanshu DK, Savithri HS, Murthy MRN. Crystal structures of Salmonella typhimurium propionate kinase and its complex with Ap4A: evidence for a novel Ap4A synthetic activity. Proteins 2008; 70:1379-88. [PMID: 17894350 DOI: 10.1002/prot.21626] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Propionate kinase catalyses the last step in the anaerobic breakdown of L-threonine to propionate in which propionyl phosphate and ADP are converted to propionate and ATP. Here we report the structures of propionate kinase (TdcD) in the native form as well as in complex with diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) by X-ray crystallography. Structure of TdcD obtained after cocrystallization with ATP showed Ap4A bound to the active site pocket suggesting the presence of Ap4A synthetic activity in TdcD. Binding of Ap4A to the enzyme was confirmed by the structure determination of a TdcD-Ap4A complex obtained after cocrystallization of TdcD with commercially available Ap4A. Mass spectroscopic studies provided further evidence for the formation of Ap4A by propionate kinase in the presence of ATP. In the TdcD-Ap4A complex structure, Ap4A is present in an extended conformation with one adenosine moiety present in the nucleotide binding site and other in the proposed propionate binding site. These observations tend to support direct in-line transfer of phosphoryl group during the kinase reaction.
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Affiliation(s)
- Dhirendra K Simanshu
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore-560 012, India
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37
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Structure and function of enzymes involved in the anaerobic degradation of L-threonine to propionate. J Biosci 2007; 32:1195-206. [PMID: 17954980 DOI: 10.1007/s12038-007-0121-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In Escherichia coli and Salmonella typhimurium, L-threonine is cleaved non-oxidatively to propionate via 2-ketobutyrate by biodegradative threonine deaminase, 2-ketobutyrate formate-lyase (or pyruvate formate-lyase), phosphotransacetylase and propionate kinase. In the anaerobic condition, L-threonine is converted to the energy-rich keto acid and this is subsequently catabolised to produce ATP via substrate-level phosphorylation, providing a source of energy to the cells. Most of the enzymes involved in the degradation of L-threonine to propionate are encoded by the anaerobically regulated tdc operon. In the recent past, extensive structural and biochemical studies have been carried out on these enzymes by various groups. Besides detailed structural and functional insights, these studies have also shown the similarities and differences between the other related enzymes present in the metabolic network. In this paper, we review the structural and biochemical studies carried out on these enzymes.
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38
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Gorrell A, Ferry JG. Investigation of the Methanosarcina thermophila acetate kinase mechanism by fluorescence quenching. Biochemistry 2007; 46:14170-6. [PMID: 17999468 DOI: 10.1021/bi701292a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Acetate kinase, a member of the acetate and sugar kinase/Hsc 70/actin (ASKHA) structural superfamily, catalyzes the reversible transfer of the gamma-phosphoryl group from ATP to acetate, yielding ADP and acetyl phosphate. A catalytic mechanism for the enzyme from Methanosarcina thermophila has been proposed on the basis of the crystal structure and kinetic analyses of amino acid replacement variants. The Gln43Trp variant was generated to further investigate the catalytic mechanism via changes in fluorescence. The dissociation constants for ADP.Mg2+ and ATP.Mg2+ ligands were determined for the Gln43Trp variant and double variants generated by replacing Arg241 and Arg91 with Ala and Lys. The dissociation constants and kinetic analyses indicated roles for the arginines in transition state stabilization for catalysis but not in nucleotide binding. The results also provide the first experimental evidence for domain motion and evidence that catalysis does not occur as two independent active sites of the homodimer but the active site activities are coordinated in a half-the-sites manner.
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Affiliation(s)
- Andrea Gorrell
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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39
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Ren NQ, Lin HL, Zhang K, Zheng GX, Duan ZJ, Lin M. Cloning, expression, and characterization of an acetate kinase from a high rate of biohydrogen bacterial strain Ethanoligenens sp. hit B49. Curr Microbiol 2007; 55:167-72. [PMID: 17619101 DOI: 10.1007/s00284-007-0172-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 03/28/2007] [Indexed: 10/23/2022]
Abstract
The acetate kinase (ack) gene from Ethanoligenens sp. hit B49, isolated from a biohydrogen production bioreactor, is a key enzyme and responsible for dephosphorylation of acetyl phosphate with the concomitant production of acetate and ATP; it was cloned, sequenced, and functionally expressed in Escherichia coli BL21(DE3). It contained a 1200-bp open reading frame and encoded a 399-amino-acid protein kinase (molecular weight, 43.22 kDa; isoionic point, pH 5.93) sharing 58% similarity with Thermotoga maritima MSB8 ack. Ack was heterologously expressed in E.coli BL21 (DE3). Ack specific activities of the refolded ack inclusion body from Ethanoligenens sp. hit B49 is 42.12 U at 25 degrees C, and the renaturation percent is 14.36%.
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Affiliation(s)
- Nan-qi Ren
- School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090 People's Republic of China
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40
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Ingram-Smith C, Martin SR, Smith KS. Acetate kinase: not just a bacterial enzyme. Trends Microbiol 2006; 14:249-53. [PMID: 16678422 DOI: 10.1016/j.tim.2006.04.001] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 03/01/2006] [Accepted: 04/10/2006] [Indexed: 11/23/2022]
Abstract
The bacterial enzymes acetate kinase (AK) and phosphotransacetylase (PTA) form a key pathway for synthesis of the central metabolic intermediate acetyl coenzyme A (acetyl-CoA) from acetate or for generation of ATP from excess acetyl-CoA. Putative AK genes have now been identified in some eukaryotic microbes. In Chlamydomonas reinhardtii and Phytophthora species, AK forms a pathway with PTA. AK has also been identified in non-yeast fungi but these fungi do not have PTA. Instead, AK forms a pathway with D-xylulose 5-phosphate phosphoketolase (XFP), a pathway that was also previously found only in bacteria. In Entamoeba histolytica, neither PTA nor XFP was found as a partner for AK. Thus, eukaryotic microbes seem to have incorporated the 'bacterial' enzyme AK into at least three different metabolic pathways.
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Affiliation(s)
- Cheryl Ingram-Smith
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC 29634-0318, USA
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Simanshu DK, Savithri HS, Murthy MRN. Crystal structures of ADP and AMPPNP-bound propionate kinase (TdcD) from Salmonella typhimurium: comparison with members of acetate and sugar kinase/heat shock cognate 70/actin superfamily. J Mol Biol 2005; 352:876-92. [PMID: 16139298 DOI: 10.1016/j.jmb.2005.07.069] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2005] [Revised: 07/27/2005] [Accepted: 07/28/2005] [Indexed: 10/25/2022]
Abstract
Recently, it has been shown that l-threonine can be catabolized non-oxidatively to propionate via 2-ketobutyrate. Propionate kinase (TdcD; EC 2.7.2.-) catalyses the last step of this metabolic process by enabling the conversion of propionyl phosphate and ADP to propionate and ATP. To provide insights into the substrate-binding pocket and catalytic mechanism of TdcD, the crystal structures of the enzyme from Salmonella typhimurium in complex with ADP and AMPPNP have been determined to resolutions of 2.2A and 2.3A, respectively, by molecular replacement using Methanosarcina thermophila acetate kinase (MAK; EC 2.7.2.1). Propionate kinase, like acetate kinase, contains a fold with the topology betabetabetaalphabetaalphabetaalpha, identical with that of glycerol kinase, hexokinase, heat shock cognaten 70 (Hsc70) and actin, the superfamily of phosphotransferases. The structure consists of two domains with the active site contained in a cleft at the domain interface. Examination of the active site pocket revealed a plausible structural rationale for the greater specificity of the enzyme towards propionate than acetate. This was further confirmed by kinetic studies with the purified enzyme, which showed about ten times lower K(m) for propionate (2.3 mM) than for acetate (26.9 mM). Comparison of TdcD complex structures with those of acetate and sugar kinase/Hsc70/actin obtained with different ligands has permitted the identification of catalytically essential residues involved in substrate binding and catalysis, and points to both structural and mechanistic similarities. In the well-characterized members of this superfamily, ATP phosphoryl transfer or hydrolysis is coupled to a large conformational change in which the two domains close around the active site cleft. The significant amino acid sequence similarity between TdcD and MAK has facilitated study of domain movement, which indicates that the conformation assumed by the two domains in the nucleotide-bound structure of TdcD may represent an intermediate point in the pathway of domain closure.
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