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Wang Q, Feng X, Liu Y, Li W, Cui W, Sun Y, Zhang S, Wang F, Xing B. Response of peanut plant and soil N-fixing bacterial communities to conventional and biodegradable microplastics. JOURNAL OF HAZARDOUS MATERIALS 2023; 459:132142. [PMID: 37515992 DOI: 10.1016/j.jhazmat.2023.132142] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/14/2023] [Accepted: 07/23/2023] [Indexed: 07/31/2023]
Abstract
Microplastics (MPs) occur and distribute widely in agroecosystems, posing a potential threat to soil-plant systems. However, little is known about their effects on legumes and N-fixing microbes. Here, we explored the effects of high-density polyethylene (HDPE), polystyrene (PS), and polylactic acid (PLA) on the growth of peanuts and soil N-fixing bacterial communities. All MPs treatments showed no phytotoxic effects on plant biomass, and PS and PLA even increased plant height, especially at the high dose. All MPs changed soil NO3--N and NH4+-N contents and the activities of urease and FDAse. Particularly, high-dose PLA decreased soil NO3--N content by 97% and increased soil urease activity by 104%. In most cases, MPs negatively affected plant N content, and high-dose PLA had the most pronounced effects. All MPs especially PLA changed soil N-fixing bacterial community structure. Symbiotic N-fixer Rhizoboales were greatly enriched by high-dose PLA, accompanied by the emergence of root nodulation, which may represent an adaptive strategy for peanuts to overcome N deficiency caused by PLA MPs pollution. Our findings indicate that MPs can change peanut-N fixing bacteria systems in a type- and dose-dependent manner, and biodegradable MPs may have more profound consequences for N biogeochemical cycling than traditional MPs.
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Affiliation(s)
- Quanlong Wang
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Xueying Feng
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Yingying Liu
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Wenguang Li
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Wenzhi Cui
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Yuhuan Sun
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Shuwu Zhang
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China
| | - Fayuan Wang
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, Shandong Province 266042, PR China.
| | - Baoshan Xing
- Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA 01003, USA
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2
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Koendjbiharie JG, van Kranenburg R, Kengen SWM. The PEP-pyruvate-oxaloacetate node: variation at the heart of metabolism. FEMS Microbiol Rev 2021; 45:fuaa061. [PMID: 33289792 PMCID: PMC8100219 DOI: 10.1093/femsre/fuaa061] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/18/2020] [Indexed: 12/15/2022] Open
Abstract
At the junction between the glycolysis and the tricarboxylic acid cycle-as well as various other metabolic pathways-lies the phosphoenolpyruvate (PEP)-pyruvate-oxaloacetate node (PPO-node). These three metabolites form the core of a network involving at least eleven different types of enzymes, each with numerous subtypes. Obviously, no single organism maintains each of these eleven enzymes; instead, different organisms possess different subsets in their PPO-node, which results in a remarkable degree of variation, despite connecting such deeply conserved metabolic pathways as the glycolysis and the tricarboxylic acid cycle. The PPO-node enzymes play a crucial role in cellular energetics, with most of them involved in (de)phosphorylation of nucleotide phosphates, while those responsible for malate conversion are important redox enzymes. Variations in PPO-node therefore reflect the different energetic niches that organisms can occupy. In this review, we give an overview of the biochemistry of these eleven PPO-node enzymes. We attempt to highlight the variation that exists, both in PPO-node compositions, as well as in the roles that the enzymes can have within those different settings, through various recent discoveries in both bacteria and archaea that reveal deviations from canonical functions.
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Affiliation(s)
- Jeroen G Koendjbiharie
- Laboratory of Microbiology, Wageningen University, Stippeneng4, 6708 WE Wageningen, The Netherlands
| | - Richard van Kranenburg
- Laboratory of Microbiology, Wageningen University, Stippeneng4, 6708 WE Wageningen, The Netherlands
- Corbion, Arkelsedijk 46, 4206 AC Gorinchem, The Netherlands
| | - Servé W M Kengen
- Laboratory of Microbiology, Wageningen University, Stippeneng4, 6708 WE Wageningen, The Netherlands
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3
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Abstract
Nitrogenase is a metalloenzyme system that plays a critical role in biological nitrogen fixation, and the study of how its metallocenters are assembled into functional entities to facilitate the catalytic reduction of dinitrogen to ammonia is an active area of interest. The diazotroph Azotobacter vinelandii is especially amenable to culturing and genetic manipulation, and this organism has provided the basis for many insights into the assembly of nitrogenase proteins and their respective metallocofactors. This chapter will cover the basic procedures necessary for growing A. vinelandii cultures and subsequent recombinant transformation and protein expression techniques. Furthermore, protocols for nitrogenase protein purification and substrate reduction activity assays are described. These methods provide a solid framework for the assessment of nitrogenase assembly and catalysis.
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Affiliation(s)
| | - Yilin Hu
- University of California, Irvine, Irvine, CA, United States.
| | - Markus W Ribbe
- University of California, Irvine, Irvine, CA, United States.
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4
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Choi PH, Jo J, Lin YC, Lin MH, Chou CY, Dietrich LEP, Tong L. A distinct holoenzyme organization for two-subunit pyruvate carboxylase. Nat Commun 2016; 7:12713. [PMID: 27708276 PMCID: PMC5059739 DOI: 10.1038/ncomms12713] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Accepted: 07/26/2016] [Indexed: 01/15/2023] Open
Abstract
Pyruvate carboxylase (PC) has important roles in metabolism and is crucial for virulence for some pathogenic bacteria. PC contains biotin carboxylase (BC), carboxyltransferase (CT) and biotin carboxyl carrier protein (BCCP) components. It is a single-chain enzyme in eukaryotes and most bacteria, and functions as a 500 kD homo-tetramer. In contrast, PC is a two-subunit enzyme in a collection of Gram-negative bacteria, with the α subunit containing the BC and the β subunit the CT and BCCP domains, and it is believed that the holoenzyme has α4β4 stoichiometry. We report here the crystal structures of a two-subunit PC from Methylobacillus flagellatus. Surprisingly, our structures reveal an α2β4 stoichiometry, and the overall architecture of the holoenzyme is strikingly different from that of the homo-tetrameric PCs. Biochemical and mutagenesis studies confirm the stoichiometry and other structural observations. Our functional studies in Pseudomonas aeruginosa show that its two-subunit PC is important for colony morphogenesis. Pyruvate carboxylases are homotetrameric enzymes in eukaryotes and most bacteria. Here, the authors report the structure of an unusual two-subunit form of the enzyme from the Gram-negative bacterium Methylobacillus flagellates, revealing an unexpected α2β4 stoichiometry.
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Affiliation(s)
- Philip H Choi
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Jeanyoung Jo
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Yu-Cheng Lin
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Min-Han Lin
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan
| | - Chi-Yuan Chou
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 112, Taiwan
| | - Lars E P Dietrich
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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5
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Affiliation(s)
- John C Wallace
- School of Molecular & Biomedical Science, University of Adelaide, Adelaide, SA, Australia.
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6
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Abstract
This review aims to discuss the varied types of inhibitors of biotin-dependent carboxylases, with an emphasis on the inhibitors of pyruvate carboxylase. Some of these inhibitors are physiologically relevant, in that they provide ways of regulating the cellular activities of the enzymes e.g. aspartate and prohibitin inhibition of pyruvate carboxylase. Most of the inhibitors that will be discussed have been used to probe various aspects of the structure and function of these enzymes. They target particular parts of the structure e.g. avidin - biotin, FTP - ATP binding site, oxamate - pyruvate binding site, phosphonoacetate - binding site of the putative carboxyphosphate intermediate.
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Affiliation(s)
- Tonya N Zeczycki
- Department of Biochemistry, University of Wisconsin, Madison, WI 53726, USA
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7
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Jitrapakdee S, Surinya KH, Adina-Zada A, Polyak SW, Stojkoski C, Smyth R, Booker GW, Cleland WW, Attwood PV, Wallace JC. Conserved Glu40 and Glu433 of the biotin carboxylase domain of yeast pyruvate carboxylase I isoenzyme are essential for the association of tetramers. Int J Biochem Cell Biol 2007; 39:2120-34. [PMID: 17659996 DOI: 10.1016/j.biocel.2007.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 05/18/2007] [Accepted: 06/03/2007] [Indexed: 11/20/2022]
Abstract
The native form of pyruvate carboxylase is an alpha4 tetramer but the tetramerisation domain of each subunit is currently unknown. To identify this domain we co-expressed yeast pyruvate carboxylase 1 isozyme (Pyc1) with an N-terminal myc tag, together with constructs encoding either the biotin carboxylase (BC) domain or the transcarboxylase-biotin carboxyl carrier domain (TC-BCC), each with an N-terminal 9-histidine tag. From tag-affinity chromatography experiments, the subunit contacts within the tetramer were identified to be primarily located in the 55 kDa BC domain. From modelling studies based on known structures of biotin carboxylase domains and subunits we have predicted that Arg36 and Glu433 and Glu40 and Lys426, respectively, are involved pairwise in subunit interactions and are located on opposing subunits in the putative subunit interface of Pyc1. Co-expression of mutant forms with wild type Pyc1 showed that the R36E mutation had no effect on the interaction of these subunits with those of wild type Pyc1, while the E40R, E433R and R36E:E433R mutations caused severe loss of interaction with wild type Pyc1. Ultracentrifugal analysis of these mutants when expressed and purified separately indicated that the predominant form of E40R, E433R and R36R:E433R mutants is the monomer, and that their specific activities are less than 2% of the wild type. Studies on the association state and specific activity of the R36E mutant at different concentrations showed it to be much more susceptible to tetramer dissociation and inactivation than the wild type. Our results suggest that Glu40 and Glu433 play essential roles in subunit interactions.
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Affiliation(s)
- Sarawut Jitrapakdee
- Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
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8
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Franke-Rinker D, Behrens U, Nöckel E, Forner C, Portnowa A. Gemeinsame Verwertung von Glucose und n-Alkanen bei der Citronensäuresynthese durch Saccharomycopsis lipolytica. J Basic Microbiol 2007. [DOI: 10.1002/jobm.19830230103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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9
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Sauer U, Eikmanns BJ. The PEP-pyruvate-oxaloacetate node as the switch point for carbon flux distribution in bacteria. FEMS Microbiol Rev 2004; 29:765-94. [PMID: 16102602 DOI: 10.1016/j.femsre.2004.11.002] [Citation(s) in RCA: 358] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2004] [Revised: 10/27/2004] [Accepted: 11/01/2004] [Indexed: 11/16/2022] Open
Abstract
In many organisms, metabolite interconversion at the phosphoenolpyruvate (PEP)-pyruvate-oxaloacetate node involves a structurally entangled set of reactions that interconnects the major pathways of carbon metabolism and thus, is responsible for the distribution of the carbon flux among catabolism, anabolism and energy supply of the cell. While sugar catabolism proceeds mainly via oxidative or non-oxidative decarboxylation of pyruvate to acetyl-CoA, anaplerosis and the initial steps of gluconeogenesis are accomplished by C3- (PEP- and/or pyruvate-) carboxylation and C4- (oxaloacetate- and/or malate-) decarboxylation, respectively. In contrast to the relatively uniform central metabolic pathways in bacteria, the set of enzymes at the PEP-pyruvate-oxaloacetate node represents a surprising diversity of reactions. Variable combinations are used in different bacteria and the question of the significance of all these reactions for growth and for biotechnological fermentation processes arises. This review summarizes what is known about the enzymes and the metabolic fluxes at the PEP-pyruvate-oxaloacetate node in bacteria, with a particular focus on the C3-carboxylation and C4-decarboxylation reactions in Escherichia coli, Bacillus subtilis and Corynebacterium glutamicum. We discuss the activities of the enzymes, their regulation and their specific contribution to growth under a given condition or to biotechnological metabolite production. The present knowledge unequivocally reveals the PEP-pyruvate-oxaloacetate nodes of bacteria to be a fascinating target of metabolic engineering in order to achieve optimized metabolite production.
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Affiliation(s)
- Uwe Sauer
- Institute of Biotechnology, ETH Zürich, Switzerland
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10
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Segura D, Espín G. Inactivation of pycA, encoding pyruvate carboxylase activity, increases poly-beta-hydroxybutyrate accumulation in Azotobacter vinelandii on solid medium. Appl Microbiol Biotechnol 2004; 65:414-8. [PMID: 15127163 DOI: 10.1007/s00253-004-1611-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2003] [Revised: 03/03/2004] [Accepted: 03/21/2004] [Indexed: 11/24/2022]
Abstract
Strain AJ1678, an Azotobacter vinelandii mutant overproducing the storage polymer poly-beta-hydroxybutyrate (PHB) in solid but not liquid complex medium with sucrose, was isolated after mini-Tn5 mutagenesis of strain UW136. Cloning and nucleotide sequencing of the affected locus led to identification of pycA, encoding a protein with high identity to the biotin carboxylase subunit of pyruvate carboxylase enzyme (PYC). A gene ( pycB) whose product is similar to the biotin-carrying subunit of PYC is present immediately downstream from pycA. An assay of pyruvate carboxylase activity and an avidin-blot analysis confirmed that pycA and pycB encode the two subunits of this enzyme. In many organisms, PYC catalyzes ATP-dependent carboxylation of pyruvate to generate oxaloacetate and is responsible for replenishing oxaloacetate for continued operation of the tricarboxylic acid cycle. We propose that the pycA mutation causes a slow-down in the TCA cycle activity due to a low oxaloacetate concentration, resulting in a higher availability of acetyl-CoA for the synthesis of poly-beta-hydroxybutyrate.
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Affiliation(s)
- D Segura
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, 62250, Cuernavaca, Morelos, Mexico
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11
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Koffas MAG, Jung GY, Aon JC, Stephanopoulos G. Effect of pyruvate carboxylase overexpression on the physiology of Corynebacterium glutamicum. Appl Environ Microbiol 2002; 68:5422-8. [PMID: 12406733 PMCID: PMC129921 DOI: 10.1128/aem.68.11.5422-5428.2002] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2002] [Accepted: 08/05/2002] [Indexed: 11/20/2022] Open
Abstract
Pyruvate carboxylase was recently sequenced in Corynebacterium glutamicum and shown to play an important role of anaplerosis in the central carbon metabolism and amino acid synthesis of these bacteria. In this study we investigate the effect of the overexpression of the gene for pyruvate carboxylase (pyc) on the physiology of C. glutamicum ATCC 21253 and ATCC 21799 grown on defined media with two different carbon sources, glucose and lactate. In general, the physiological effects of pyc overexpression in Corynebacteria depend on the genetic background of the particular strain studied and are determined to a large extent by the interplay between pyruvate carboxylase and aspartate kinase activities. If the pyruvate carboxylase activity is not properly matched by the aspartate kinase activity, pyc overexpression results in growth enhancement instead of greater lysine production, despite its central role in anaplerosis and aspartic acid biosynthesis. Aspartate kinase regulation by lysine and threonine, pyruvate carboxylase inhibition by aspartate (shown in this study using permeabilized cells), as well as well-established activation of pyruvate carboxylase by lactate and acetyl coenzyme A are the key factors in determining the effect of pyc overexpression on Corynebacteria physiology.
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Affiliation(s)
- Mattheos A G Koffas
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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12
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Velayudhan J, Kelly DJ. Analysis of gluconeogenic and anaplerotic enzymes in Campylobacter jejuni: an essential role for phosphoenolpyruvate carboxykinase. MICROBIOLOGY (READING, ENGLAND) 2002; 148:685-694. [PMID: 11882702 DOI: 10.1099/00221287-148-3-685] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Campylobacter jejuni is unable to utilize glucose as a carbon source due to the absence of the key glycolytic enzyme 6-phosphofructokinase. The genome sequence of C. jejuni NCTC 11168 indicates that homologues of all the appropriate enzymes for gluconeogenesis from phosphoenolpyruvate (PEP) are present, in addition to the anaplerotic enzymes pyruvate carboxylase (PYC), phosphoenolpyruvate carboxykinase (PCK) and malic enzyme (MEZ). Surprisingly, a pyruvate kinase (PYK) homologue is also present. To ascertain the role of these enzymes, insertion mutants in pycA, pycB, pyk and mez were generated. However, this could not be achieved for pckA, indicating that PCK is an essential enzyme in C. jejuni. The lack of PEP synthase and pyruvate orthophosphate dikinase activities confirmed a unique role for PCK in PEP synthesis. The pycA mutant was unable to grow in defined medium with pyruvate or lactate as the major carbon source, thus indicating an important role for PYC in anaplerosis. Sequence and biochemical data indicate that the PYC of C. jejuni is a member of the alpha4beta4, acetyl-CoA-independent class of PYCs, with a 65.8 kDa subunit containing the biotin moiety. Whereas growth of the mez mutant was comparable to that of the wild-type, the pyk mutant displayed a decreased growth rate in complex medium. Nevertheless, the mez and pyk mutants were able to grow with pyruvate, lactate or malate as carbon sources in defined medium. PYK was present in cell extracts at a much higher specific activity [>800 nmol x min(-1) x (mg protein)(-1)] than PYC or PCK [<65 nmol x min(-1) x (mg protein)(-1)], was activated by fructose 1,6-bisphosphate and displayed other regulatory properties strongly indicative of a catabolic role. It is concluded that PYK may function in the catabolism of unidentified substrates which are metabolized through PEP. In view of the high K(m) of MEZ for malate (approximately 9 mM) and the lack of a growth phenotype of the mez mutant, MEZ seems to have only a minor anaplerotic role in C. jejuni.
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Affiliation(s)
- Jyoti Velayudhan
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK1
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13
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A. Osmani S, C. Scrutton M. Activation of pyruvate carboxylase from aspergillus nidulans
by acetyl coenzyme A. FEBS Lett 2001. [DOI: 10.1016/0014-5793(81)80794-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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14
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Abstract
Pyruvate carboxylase (PC; EC 6.4.1.1), a member of the biotin-dependent enzyme family, catalyses the ATP-dependent carboxylation of pyruvate to oxaloacetate. PC has been found in a wide variety of prokaryotes and eukaryotes. In mammals, PC plays a crucial role in gluconeogenesis and lipogenesis, in the biosynthesis of neurotransmitter substances, and in glucose-induced insulin secretion by pancreatic islets. The reaction catalysed by PC and the physical properties of the enzyme have been studied extensively. Although no high-resolution three-dimensional structure has yet been determined by X-ray crystallography, structural studies of PC have been conducted by electron microscopy, by limited proteolysis, and by cloning and sequencing of genes and cDNA encoding the enzyme. Most well characterized forms of active PC consist of four identical subunits arranged in a tetrahedron-like structure. Each subunit contains three functional domains: the biotin carboxylation domain, the transcarboxylation domain and the biotin carboxyl carrier domain. Different physiological conditions, including diabetes, hyperthyroidism, genetic obesity and postnatal development, increase the level of PC expression through transcriptional and translational mechanisms, whereas insulin inhibits PC expression. Glucocorticoids, glucagon and catecholamines cause an increase in PC activity or in the rate of pyruvate carboxylation in the short term. Molecular defects of PC in humans have recently been associated with four point mutations within the structural region of the PC gene, namely Val145-->Ala, Arg451-->Cys, Ala610-->Thr and Met743-->Thr.
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Affiliation(s)
- S Jitrapakdee
- Department of Biochemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
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15
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Peters-Wendisch PG, Kreutzer C, Kalinowski J, Pátek M, Sahm H, Eikmanns BJ. Pyruvate carboxylase from Corynebacterium glutamicum: characterization, expression and inactivation of the pyc gene. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 4):915-927. [PMID: 9579065 DOI: 10.1099/00221287-144-4-915] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In addition to phosphoenolpyruvate carboxylase (PEPCx), pyruvate carboxylase (PCx) has recently been found as an anaplerotic enzyme in the amino-acid-producing bacterium Corynebacterium glutamicum. Using oligonucleotides designed according to conserved regions of PCx amino acid sequences from other organisms, a 200 bp fragment central to the C. glutamicum PCx gene (pyc) was amplified from genomic DNA by PCR. This fragment was then used to identify and to subclone the entire C. glutamicum pyc gene. The cloned pyc gene was expressed in C. glutamicum, as cells harbouring the gene on plasmid showed four- to fivefold higher specific PCx activities when compared to the wild-type (WT). Moreover, increased PCx protein levels in the pyc-plasmid-carrying strain were readily detected after SDS-PAGE of cell-free extracts. DNA sequence analysis of the pyc gene, including its 5' and 3' flanking regions, and N-terminal sequencing of the pyc gene product predicts a PCx polypeptide of 1140 amino acids with an M(r) of 123070. The amino acid sequence of this polypeptide shows between 62% and 45% identity when compared to PCx enzymes from other organisms. Transcriptional analyses revealed that the pyc gene from C. glutamicum is monocistronic (3.5 kb mRNA) and that its transcription is initiated at an A residue 55 bp upstream of the translational start. Inactivation of the chromosomal pyc gene in C. glutamicum WT led to the absence of PCx activity and to negligible growth on lactate, indicating that PCx is essential for growth on this carbon source. Inactivation of both the PCx gene and the PEPCx gene in C. glutamicum led additionally to the inability to grow on glucose, indicating that no further anaplerotic enzymes for growth on carbohydrates exist in this organism.
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Affiliation(s)
| | - Caroline Kreutzer
- Institut für Biotechnologie, Forschungszentrum Jülich, D-52425 Julich, Germany
| | - Jörn Kalinowski
- Lehrstuhl für Genetik, Universität Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany
| | - Miroslav Pátek
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídenská 1083, CZ-14220 Prague, Czech Republic
| | - Hermann Sahm
- Institut für Biotechnologie, Forschungszentrum Jülich, D-52425 Julich, Germany
| | - Bernhard J Eikmanns
- Institut für Biotechnologie, Forschungszentrum Jülich, D-52425 Julich, Germany
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16
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Mukhopadhyay B, Stoddard SF, Wolfe RS. Purification, regulation, and molecular and biochemical characterization of pyruvate carboxylase from Methanobacterium thermoautotrophicum strain deltaH. J Biol Chem 1998; 273:5155-66. [PMID: 9478969 DOI: 10.1074/jbc.273.9.5155] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
We discovered that Methanobacterium thermoautotrophicum strain DeltaH possessed pyruvate carboxylase (PYC), and this biotin prototroph required exogenously supplied biotin to exhibit detectable amounts of PYC activity. The enzyme was highly labile and was stabilized by 10% inositol in buffers to an extent that allowed purification to homogeneity and characterization. The purified enzyme was absolutely dependent on ATP, Mg2+ (or Mn2+ or Co2+), pyruvate, and bicarbonate for activity; phosphoenolpyruvate could not replace pyruvate, and acetyl-CoA was not required. The enzyme was inhibited by ADP and alpha-ketoglutarate but not by aspartate or glutamate. ATP was inhibitory at high concentrations. The enzyme, unlike other PYCs, exhibited nonlinear kinetics with respect to bicarbonate and was inhibited by excess Mg2+, Mn2+, or Co2+. The 540-kDa enzyme of A4B4 composition contained a non-biotinylated 52-kDa subunit (PYCA) and a 75-kDa biotinylated subunit (PYCB). The pycB gene was probably monocistronic and followed by a putative gene of a DNA-binding protein on the opposite strand. The pycA was about 727 kilobase pairs away from pycB on the chromosome and was probably co-transcribed with the biotin ligase gene (birA). PYCA and PYCB showed substantial sequence identities (33-62%) to, respectively, the biotin carboxylase and biotin carboxyl carrier + carboxyltransferase domains or subunits of known biotin-dependent carboxylases/decarboxylases. We discovered that PYCB and probably the equivalent domains or subunits of all biotin-dependent carboxylases harbored the serine/threonine dehydratase types of pyridoxal-phosphate attachment site. Our results and the existence of an alternative oxaloacetate synthesizing enzyme phosphoenolpyruvate carboxylase in M. thermoautotrophicum strain DeltaH (Kenealy, W. R., and Zeikus, J. G. (1982) FEMS Microbiol. Lett. 14, 7-10) raise several questions for future investigations.
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Affiliation(s)
- B Mukhopadhyay
- Department of Microbiology, University of Illinois, Urbana, Illinois 61801, USA.
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17
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Peters-Wendisch PG, Wendisch VF, Paul S, Eikmanns BJ, Sahm H. Pyruvate carboxylase as an anaplerotic enzyme in Corynebacterium glutamicum. Microbiology (Reading) 1997; 143:1095-1103. [DOI: 10.1099/00221287-143-4-1095] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The recent discovery that phosphoenolpyruvate carboxylase (PEPCx) is dispensable for growth and lysine production in Corynebacterium glutamicum implies that this organism possesses (an) alternative anaplerotic enzyme(s). In permeabilized cells of C. glutamicum, we detected pyruvate carboxylase (PCx) activity. This activity was effectively inhibited by low concentrations of ADP, AMP and acetyl-CoA. PCx activity was highest [45 ± 5 nmol min−1 (mg dry wt)−1] in cells grown on lactate or pyruvate, and was about two- to threefold lower when the cells were grown on glucose or acetate, suggesting that formation of PCx is regulated by the carbon source in the growth medium. In cells grown at low concentrations of biotin (< 5 μg I−1), PCx activity was drastically reduced, indicating that the enzyme is a biotin protein. Growth experiments with the wild-type and a defined PEPCx-negative mutant of C. glutamicum on glucose showed that the mutant has a significantly higher demand for biotin than the wild-type, whereas both strains have the same high biotin requirement for growth on lactate and the same low biotin requirement for growth on acetate. These results indicate that (i) PCx is an essential anaplerotic enzyme for growth on glucose in the absence of PEPCx, (ii) PCx is an essential anaplerotic enzyme for growth on lactate even in the presence of PEPCx, and (iii) PCx has no anaplerotic significance for growth on acetate as the carbon source. In support of these conclusions, screening for clones unable to grow on a minimal medium containing lactate, but able to grow on a medium containing glucose or acetate, led to the isolation of PCx-defective mutants of C. glutamicum.
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Affiliation(s)
| | - Volker F. Wendisch
- Institut für Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | - Susanne Paul
- Institut für Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | | | - Hermann Sahm
- Institut für Biotechnologie, Forschungszentrum Jülich, D-52425 Jülich, Germany
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Yakunin AF, Hallenbeck PC. Regulation of synthesis of pyruvate carboxylase in the photosynthetic bacterium Rhodobacter capsulatus. J Bacteriol 1997; 179:1460-8. [PMID: 9045800 PMCID: PMC178853 DOI: 10.1128/jb.179.5.1460-1468.1997] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The synthesis of pyruvate carboxylase (PC) was studied by using quantitative immunoblot analysis with an antibody raised against PC purified from Rhodobacter capsulatus and was found to vary 20-fold depending on the growth conditions. The PC content was high in cells grown on pyruvate or on carbon substrates metabolized via pyruvate (lactate, D-malate, glucose, or fructose) and low in cells grown on tricarboxylic acid (TCA) cycle intermediates or substrates metabolized without intermediate formation of pyruvate (acetate or glutamate). Under dark aerobic growth conditions with lactate as a carbon source, the PC content was approximately twofold higher than that found under light anaerobic growth conditions. The results of incubation experiments demonstrate that PC synthesis is induced by pyruvate and repressed by TCA cycle intermediates, with negative control dominating over positive control. The content of PC in R. capsulatus cells was also directly related to the growth rate in continuous cultures. The analysis of intracellular levels of pyruvate and TCA cycle intermediates in cells grown under different conditions demonstrated that the content of PC is directly proportional to the ratio between pyruvate and C4 dicarboxylates. These results suggest that the regulation of PC synthesis by oxygen and its direct correlation with growth rate may reflect effects on the balance of intracellular pyruvate and C4 dicarboxylates. Thus, this important enzyme is potentially regulated both allosterically and at the level of synthesis.
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Affiliation(s)
- A F Yakunin
- Département de Microbiologie et Immunologie, Université de Montreal, Québec, Canada
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19
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Dunn MF, Encarnación S, Araíza G, Vargas MC, Dávalos A, Peralta H, Mora Y, Mora J. Pyruvate carboxylase from Rhizobium etli: mutant characterization, nucleotide sequence, and physiological role. J Bacteriol 1996; 178:5960-70. [PMID: 8830693 PMCID: PMC178453 DOI: 10.1128/jb.178.20.5960-5970.1996] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Pyruvate carboxylase (PYC), a biotin-dependent enzyme which catalyzes the conversion of pyruvate to oxaloacetate, was hypothesized to play an important anaplerotic role in the growth of Rhizobium etli during serial subcultivation in minimal media containing succinate (S. Encarnación, M. Dunn, K. Willms, and J. Mora, J. Bacteriol. 177:3058-3066, 1995). R. etli and R. tropici pyc::Tn5-mob mutants were selected for their inability to grow in minimal medium with pyruvate as a sole carbon source. During serial subcultivation in minimal medium containing 30 mM succinate, the R. etli parent and pyc mutant strains exhibited similar decreases in growth rate with each subculture. Supplementation of the medium with biotin prevented the growth decrease of the parent but not the mutant strain, indicating that PYC was necessary for the growth of R. etli under these conditions. The R. tropici pyc mutant grew normally in subcultures regardless of biotin supplementation. The symbiotic phenotypes of the pyc mutants from both species were similar to those of the parent strains. The R. etli pyc was cloned, sequenced, and found to encode a 126-kDa protein of 1,154 amino acids. The deduced amino acid sequence is highly homologous to other PYC sequences, and the catalytic domains involved in carboxylation, pyruvate binding, and biotinylation are conserved. The sequence and biochemical data show that the R. etli PYC is a member of the alpha4, homotetrameric, acetyl coenzyme A-activated class of PYCs.
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Affiliation(s)
- M F Dunn
- Departamento de Ecología Molecular, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Cuernavaca, Morelos.
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Jetten MSM, Pitoc GA, Follettie MT, Sinskey AJ. Regulation of phospho(enol)-pyruvate-and oxaloacetate-converting enzymes in Corynebacterium glutamicum. Appl Microbiol Biotechnol 1994. [DOI: 10.1007/bf00166080] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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21
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Jetten MS, Sinskey AJ. Characterization of phosphoenolpyruvate carboxykinase fromCorynebacterium glutamicum. FEMS Microbiol Lett 1993. [DOI: 10.1111/j.1574-6968.1993.tb06383.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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22
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O'Regan M, Thierbach G, Bachmann B, Villeval D, Lepage P, Viret JF, Lemoine Y. Cloning and nucleotide sequence of the phosphoenolpyruvate carboxylase-coding gene of Corynebacterium glutamicum ATCC13032. Gene 1989; 77:237-51. [PMID: 2666264 DOI: 10.1016/0378-1119(89)90072-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
As a first step in determining the importance of the anaplerotic function of phosphoenolpyruvate carboxylase (PEPC) in amino acid biosynthesis, the ppc gene coding for PEPC of Corynebacterium glutamicum ATCC13032 has been cloned by complementation of an Escherichia coli ppc mutant strain. PEPC activity encoded by the cloned gene is not affected by acetyl-CoA under conditions where the E. coli enzyme is strongly activated, whereas acetyl-CoA is able to relieve inhibition by L-aspartate used singly or in combination with alpha-ketoglutarate. Amplification of the ppc gene in a C. glutamicum lysine-excreting strain resulted in increased PEPC-specific activity and lysine productivity. The nucleotide sequence of a DNA fragment of 4885 bp encompassing the ppc gene has been determined. At the amino acid level, PEPC from C. glutamicum presents overall a high degree of similarity with corresponding enzymes from three different organisms. The location of some strictly conserved regions may have important implications for PEPC activity and allostery.
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Affiliation(s)
- M O'Regan
- Degussa AG/Asta Pharma AG, Halle-Kûnsebeck F.R.G
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Trotsenko Y, Doronina N, Govorukhina N. Metabolism of non-motile obligately methylotrophic bacteria. FEMS Microbiol Lett 1986. [DOI: 10.1111/j.1574-6968.1986.tb01290.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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24
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Nishikawa K, Kuwana H. Localization of pyruvate carboxylase in the cells of Neurospora crassa. EXPERIENTIA 1984; 40:356-7. [PMID: 6232147 DOI: 10.1007/bf01952549] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The cell wall of Neurospora crassa was digested enzymatically and the cytosolic and the mitochondrial fractions were separated. The activity of pyruvate carboxylase (EC 6.4.1.1) was detected entirely in the cytosolic fraction. This indicates that the location of pyruvate carboxylase of N. crassa is in the cytosol, but is not in the mitochondria; this is different from the situation in animal tissues.
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Franke-Rinker D, Behrens U, Nöckel E, Forner C, Portnowa A. [Joint utilization of glucose and n-alkanes in citric acid synthesis by Saccharomycopsis lipolytica]. ZEITSCHRIFT FUR ALLGEMEINE MIKROBIOLOGIE 1983; 23:9-16. [PMID: 6868651 DOI: 10.1002/jobm.3630230103] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Fermentations for the overproduction of citrate and isocitrate with S. lipolytica in media containing both glucose and n-alkanes as mixed C-source have been performed. Biomass and product yields strongly depend on the C-source of the inoculation culture. If the inoculation culture had been taken from media containing glucose as sole C-source both glucose and n-alkanes were utilized for cell growth in the main culture whereas only glucose was utilized if the inoculation medium contained only n-alkanes. For idiophasic citrate and isocitrate production both glucose and n-alkanes were consumed independently of the C-source of the inoculum but that C-source was preferentially utilized which has been the C-source of the inoculation culture. These findings are reflected by the activities of the isocitrate lyase and the pyruvate carboxylase, respectively. In S. lipolytica both anaplerotic pathways are coexisting but the C-source of the inoculation culture determines the level of the specific activities even if the ratio of the cell-mass of the inoculum to the cell mass of the main culture at the end of the growth phase is about 1:35.
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Osmani SA, Marston FA, Selmes IP, Chapman AG, Scrutton MC. Pyruvate carboxylase from Aspergillus nidulans. Regulatory properties. EUROPEAN JOURNAL OF BIOCHEMISTRY 1981; 118:271-8. [PMID: 7026241 DOI: 10.1111/j.1432-1033.1981.tb06396.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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28
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Charles A, Butler B, Willer D. Pyruvate carboxylase from the facultative chemolithotrophs Thiobacillus A2and Thiobacillus novellus. FEMS Microbiol Lett 1980. [DOI: 10.1111/j.1574-6968.1980.tb05020.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Scrutton MC. Fine control of the conversion of pyruvate (phosphoenolypyruvate) to oxaloacetate in various species. FEBS Lett 1978; 89:1-9. [PMID: 350618 DOI: 10.1016/0014-5793(78)80510-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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30
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Taylor B, Frey W, Barden R, Scrutton M, Utter M. The use of the ultracentrifuge to determine the catalytically competent forms of enzymes with more than one oligomeric structure. Multiple reacting forms of pyruvate carboxylase from chicken and rat liver. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)40803-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Gurr JA, Jones KM. Purification and characterization of pyruvate carboxylase from Arthrobacter globiformis. Arch Biochem Biophys 1977; 179:444-55. [PMID: 851353 DOI: 10.1016/0003-9861(77)90132-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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32
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O'Brien R, Chuang DT, Taylor BL, Utter MF. Novel enzymic machinery for the metabolism of oxalacetate, phosphoenolpyruvate, and pyruvate in Pseudomonas citronellolis. J Biol Chem 1977. [DOI: 10.1016/s0021-9258(17)40649-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Gottschalk EM, Mayer F, Klostermann A, Seubert W. Determination of molecular weight and molecular structure of rat-liver pyruvate carboxylase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1976; 64:411-21. [PMID: 1278167 DOI: 10.1111/j.1432-1033.1976.tb10317.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The molecular weight of pyruvate carboxylase isolated from pigeon and rat liver mitochondria was examined using analytical ultracentrifugation and electron microscopy. The enzyme molecule appeared as a tetramer with the four subunits arranged at the corners of a square. Sedimentation studies in the analytical ultracentrifuge, extrapolated to infinite dilution, showed the tetramer to have a molecular weight Mc=0r of 280 000 and an So20,w of 12.7 S. The tetramer could be dissociated into trimers and dimers of lower specific enzymic activity by storage at 4 degrees C or incubation at -- 20 degrees C at low protein concentrations. The isolated trimers and dimers had a molecular weight Mc=0r of 210 000 and 140 000, respectively, and an So20,w of 10.85 S and 7.55 S, respectively. Incubation with 2 M urea at 20 degrees C yielded enzymically inactive subunits (Mc=0r = 70 000; So20,w = 4.95 S). The molecular weights (for pyruvate carboxylase and its subunits), as calculated from the subunit diameter observed in the electron microscope, were consistent with the values obtained from sedimentation studies.
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Bridger GP, Sundaram TK. Occurrence of phosphenolpyruvate carboxylase in the extremely thermophilic bacterium Thermus aquaticus. J Bacteriol 1976; 125:1211-3. [PMID: 1254553 PMCID: PMC236202 DOI: 10.1128/jb.125.3.1211-1213.1976] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In the extreme thermophile Thermus aquaticus, phosphoenolpyruvate carboxylase catalyzes carbon dioxide fixation on the C3 metabolite phosphoenolpyruvate, producing oxaloacetate. In a moderately thermophilic Bacillus species this function is fulfilled by pyruvate carboyxlase. Like several of its mesophilic counterparts, the Thermus enzyme exhibits a requirement for acetyl coenzyme A.
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Scrutton MC, Fatebene F. An assay system for localisation of pyruvate and phosphoenolpyruvate carboxylase activity on polyacrylamide gels and its application to detection of these enzymes in tissue and cell extracts. Anal Biochem 1975; 69:247-60. [PMID: 1108699 DOI: 10.1016/0003-2697(75)90584-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Barden RE, Taylor BL, Isoashi F, Frey WH, Zander G, Lee JC, Utter MF. Structural properties of pyruvate carboxylases from chicken liver and other sources. Proc Natl Acad Sci U S A 1975; 72:4308-12. [PMID: 1105579 PMCID: PMC388710 DOI: 10.1073/pnas.72.11.4308] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Varieties of pyruvate carboxylase [pyruvate: CO2 ligase (ADP-forming), EC 6.4.1.1] obtained from the livers of several species of vertebrates, including humans, all show the same basic structure. They are composed of large polypeptide chains of molecular weights ranging from 1.2 to 1.3 X 10(5) for the different varieties of the enzyme. The native form of the enzyme appears to be a tetramer with a molecular weight of about 5 X 10(5). In the case of pyruvate carboxylase from chicken liver each polypeptide chain contains a biotin moiety, thus supporting the thesis that the tetramer contains four identical polypeptide chains. Pyruvate carboxylase from yeast appears to be basically similar to those from the vertebrate species and has a tetrameric structure. Each protomer contains a single polypeptide chain with a molecular weitht of 1.25 X 10(5). In contrast, pyruvate carboxylase from two bacterial species, Pseudomonas citronellolis and Axotobacter vinelandii, appears to be a dimer with a molecular weight (2.5 X 10(5)) about half that of the animal and yeast species. As a further difference, each of the protomers of the bacterial enzymes contain two polypeptides of 6.5 and 5.4 X 10(5) molecular weight in case of the Pseudomonas enzyme. The larger of the two polypeptides contains the biotin moiety. The functional units of the bacterial enzyme thus appear to contain two polypeptides while that of the liver and yeast enzymes is made up of a single chain. Neither of these arrangements corresponds with those of other biotin enzymes whose structure has been extensively studied (acetyl-CoA carboxylases from liver or Excherichia coli, and transcarboxylase from Propionibacterium).
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Scrutton MC. A plea for a comparative approach to evaluation of the physiological significance of regulatory mechanism observed in in vitro studies. Med Hypotheses 1975; 1:207-13. [PMID: 1228372 DOI: 10.1016/0306-9877(75)90004-3] [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: 12/26/2022]
Abstract
Regulatory mechanisms proposed on the vasis of in vitro studies using purified enzymes should be evaluated for their physiological significance in different species and under various conditions. The procedures presently employed for such evaluation are examined, and it is suggested that difficulties of application or interpretation arise, especially in studies on highly differentiated organisms. The use of comparative enzymology as an alternative approach to this problem is proposed, using in the main data obtained in studies on pyruvate carboxylase to illustrate the potential of this method. Some problems which arise in the use of comparative studies in this context are considered.
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Schindler PW, Scrutton MC. Mode of action of the macrolide-type antibiotic, chlorothricin. Effect of the antibiotic on the catalytic activity and some structural parameters of pyruvate carboxylases purified from rat and chicken liver. EUROPEAN JOURNAL OF BIOCHEMISTRY 1975; 55:543-53. [PMID: 1175611 DOI: 10.1111/j.1432-1033.1975.tb02191.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The macrolide-type antibiotic chlorothricin inhibits pyruvate carboxylases purified from rat liver, chicken liver and Azotobacter vinelandii. Under standard assay conditions the concentration of chlorothricin required for half-maximal inhibition of oxalacetate synthesis is 0.26 mM (rat liver), 0.12 mM (chicken liver), and 0.5 mM (Azobacter vinelandii). Inhibition by chlorothricin appears non-competitive in character when measured as a function of the concentration of the substrates of the pyruvate carboxylase reaction as well as of CoASAc and Mg2+. This pattern of inhibition suggests that this antibiotic interacts at unique sites on chicken and rat liver pyruvate carboxylase which are distinct from both the catalytic and activator sites. Interaction of chlorothricin with the two vertebrate liver pyruvate carboxylases differs from the effect exerted by this antibiotic on pyruvate carboxylase purified from Azotobacter vinelandii. A sigmoidal relationship between initial velocity and inhibitor concentration is observed for the vertebrate enzymes under most conditions whereas a hyperbolic profile characterizes the concentration dependence of inhibition of the Azotobacter vinelandii enzyme by chlorothricin. In the case of rat liver pyruvate carboxylase chlorothricin does not alter the extent of cooperativity in the relationship between initial rate and CoASAc concentration. However, a small but significant increase of the Hill coefficient from a value of 2.7 in the absence of antibiotic to that of 3.3 in the presence of 0.5 mM chlorothricin is observed for chicken liver pyruvate carboxylase. Chlorothricin decreases the rate of inactivation observed when rat liver pyruvate carboxylase is incubated with trinitrobenzenesulfonate and when chicken liver pyruvate carboxylase is incubated at 2 degrees C. The maximal decrease in inactivation observed in the presence of saturating concentrations of antibiotic is 50% for cold inactivation of the chicken liver enzyme and 60% for inactivation of the enzyme from rat liver by trinitrobenzenesulfonate. In both cases a sigmoidal relationship is observed between inactivation rate and chlorothricin concentration. These data as well as the initial rate studies suggest that multiple interacting sites for this antibiotic are present on the vertebrate liver pyruvate carboxylases. The occupancy of these sites appears to cause significant distortion of both the catalytic and the activator sites.
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