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Caballero Cerbon DA, Widmann J, Weuster-Botz D. Metabolic control analysis enabled the improvement of the L-cysteine production process with Escherichia coli. Appl Microbiol Biotechnol 2024; 108:108. [PMID: 38212968 PMCID: PMC10784400 DOI: 10.1007/s00253-023-12928-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 09/14/2023] [Accepted: 09/30/2023] [Indexed: 01/13/2024]
Abstract
L-cysteine is an amino acid with relevance to the pharmaceutical, food, feed, and cosmetic industry. The environmental and societal impact of its chemical production has led to the development of more sustainable fermentative L-cysteine production processes with engineered E. coli based on glucose and thiosulfate as sulphur source. Still, most of the published processes show low yields. For the identification of further metabolic engineering targets, engineered E. coli cells were withdrawn from a fed-batch production process, followed by in vivo metabolic control analysis (MCA) based on the data of short-term perturbation experiments, metabolomics (LC-MS), and thermodynamic flux analysis (TFA). In vivo MCA indicated that the activities of the L-cysteine synthases of the cells withdrawn from the production process might be limiting, and we hypothesised that the L-cysteine precursor O-acetylserine (OAS) might be exported from the cells faster than it took to transform OAS into L-cysteine. By increasing the expression of the L-cysteine synthases, either sulfocysteine synthase or L-cysteine synthase, which transform OAS into L-cysteine, an improvement of up to 70% in specific L-cysteine productivity and up to 47% in the final L-cysteine concentration was achieved in standardised fed-batch processes thereby increasing the yield on glucose by more than 85 to 9.2% (w/w). KEY POINTS: • Metabolic control analysis was applied to analyse L-cysteine production with E. coli • OAS export was faster than its transformation to L-cysteine • Overexpression of L-cysteine synthases improved L-cysteine productivity and yield.
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Affiliation(s)
- Daniel Alejandro Caballero Cerbon
- Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, Boltzmannstr. 15, 85748, Garching, Germany
| | - Jeremias Widmann
- Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, Boltzmannstr. 15, 85748, Garching, Germany
| | - Dirk Weuster-Botz
- Chair of Biochemical Engineering, School of Engineering and Design, Technical University of Munich, Boltzmannstr. 15, 85748, Garching, Germany.
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Kugler A, Stensjö K. Machine learning predicts system-wide metabolic flux control in cyanobacteria. Metab Eng 2024; 82:171-182. [PMID: 38395194 DOI: 10.1016/j.ymben.2024.02.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 02/14/2024] [Accepted: 02/20/2024] [Indexed: 02/25/2024]
Abstract
Metabolic fluxes and their control mechanisms are fundamental in cellular metabolism, offering insights for the study of biological systems and biotechnological applications. However, quantitative and predictive understanding of controlling biochemical reactions in microbial cell factories, especially at the system level, is limited. In this work, we present ARCTICA, a computational framework that integrates constraint-based modelling with machine learning tools to address this challenge. Using the model cyanobacterium Synechocystis sp. PCC 6803 as chassis, we demonstrate that ARCTICA effectively simulates global-scale metabolic flux control. Key findings are that (i) the photosynthetic bioproduction is mainly governed by enzymes within the Calvin-Benson-Bassham (CBB) cycle, rather than by those involve in the biosynthesis of the end-product, (ii) the catalytic capacity of the CBB cycle limits the photosynthetic activity and downstream pathways and (iii) ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is a major, but not the most, limiting step within the CBB cycle. Predicted metabolic reactions qualitatively align with prior experimental observations, validating our modelling approach. ARCTICA serves as a valuable pipeline for understanding cellular physiology and predicting rate-limiting steps in genome-scale metabolic networks, and thus provides guidance for bioengineering of cyanobacteria.
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Affiliation(s)
- Amit Kugler
- Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, SE-751 20, Uppsala, Sweden
| | - Karin Stensjö
- Microbial Chemistry, Department of Chemistry-Ångström Laboratory, Uppsala University, Box 523, SE-751 20, Uppsala, Sweden.
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Mazat JP. The metabolic control theory: Its development and its application to mitochondrial oxidative phosphorylation. Biosystems 2023; 234:105038. [PMID: 37838015 DOI: 10.1016/j.biosystems.2023.105038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 09/08/2023] [Accepted: 09/21/2023] [Indexed: 10/16/2023]
Abstract
Metabolic Control Theory (MCT) and Metabolic Control Analysis (MCA) are the two sides, theoretical and experimental, of the measurement of the sensitivity of metabolic networks in the vicinity of a steady state. We will describe the birth and the development of this theory from the first analyses of linear pathways up to a global mathematical theory applicable to any metabolic network. We will describe how the theory, given the global nature of mitochondrial oxidative phosphorylation, solved the problem of what controls mitochondrial ATP synthesis and then how it led to a better understanding of the differential tissue expression of human mitochondrial pathologies and of the heteroplasmy of mitochondrial DNA, leading to the concept of the threshold effect.
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Affiliation(s)
- Jean-Pierre Mazat
- IBGC CNRS UMR 5095 & Université de Bordeaux, 1, rue Camille Saint-Saëns, 33077, BORDEAUX Cedex, France.
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Puurand M, Tepp K, Kaambre T. Diving into cancer OXPHOS - The application of metabolic control analysis to cell and tissue research. Biosystems 2023; 233:105032. [PMID: 37739307 DOI: 10.1016/j.biosystems.2023.105032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 08/30/2023] [Accepted: 09/12/2023] [Indexed: 09/24/2023]
Abstract
Knowing how the oxidative phosphorylation (OXPHOS) system in cancer cells operates differently from that of normal cells would help find compounds that specifically paralyze the energy metabolism of cancer cells. The first experiments in the study of mitochondrial respiration using the metabolic control analysis (MCA) method were done with isolated liver mitochondria in the early 80s of the last century. Subsequent studies have shown that the regulation of mitochondrial respiration by ADP in isolated mitochondria differs significantly from a model of mitochondria in situ, where the contacts with components in the cytoplasm are largely preserved. The method of selective permeabilization of the outer membrane of the cells allows the application of MCA to evaluate the contribution of different components of the OXPHOS system to its functioning while mitochondria are in a natural state. In this review, we summarize the use of MCA to study OXPHOS in cancer using permeabilized cells and tissues. In addition, we give examples of how this data fits into cancer research with a completely different approach and methodology.
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Affiliation(s)
- Marju Puurand
- Laboratory of Chemical Biology, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia.
| | - Kersti Tepp
- Laboratory of Chemical Biology, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Tuuli Kaambre
- Laboratory of Chemical Biology, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
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Westerhoff HV. On paradoxes between optimal growth, metabolic control analysis, and flux balance analysis. Biosystems 2023; 233:104998. [PMID: 37591451 DOI: 10.1016/j.biosystems.2023.104998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 08/04/2023] [Accepted: 08/08/2023] [Indexed: 08/19/2023]
Abstract
In Microbiology it is often assumed that growth rate is maximal. This may be taken to suggest that the dependence of the growth rate on every enzyme activity is at the top of an inverse-parabolic function, i.e. that all flux control coefficients should equal zero. This might seem to imply that the sum of these flux control coefficients equals zero. According to the summation law of Metabolic Control Analysis (MCA) the sum of flux control coefficients should equal 1 however. And in Flux Balance Analysis (FBA) catabolism is often limited by a hard bound, causing catabolism to fully control the fluxes, again in apparent contrast with a flux control coefficient of zero. Here we resolve these paradoxes (apparent contradictions) in an analysis that uses the 'Edinburgh pathway', the 'Amsterdam pathway', as well as a generic metabolic network providing the building blocks or Gibbs energy for microbial growth. We review and show that (i) optimization depends on so-called enzyme control coefficients rather than the 'catalytic control coefficients' of MCA's summation law, (ii) when optimization occurs at fixed total protein, the former differ from the latter to the extent that they may all become equal to zero in the optimum state, (iii) in more realistic scenarios of optimization where catalytically inert biomass is compensating or maintenance metabolism is taken into consideration, the optimum enzyme concentrations should not be expected to equal those that maximize the specific growth rate, (iv) optimization may be in terms of yield rather than specific growth rate, which resolves the paradox because the sum of catalytic control coefficients on yield equals 0, (v) FBA effectively maximizes growth yield, and for yield the summation law states 0 rather than 1, thereby removing the paradox, (vi) furthermore, FBA then comes more often to a 'hard optimum' defined by a maximum catabolic flux and a catabolic-enzyme control coefficient of 1. The trade-off between maintenance metabolism and growth is highlighted as worthy of further analysis.
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Affiliation(s)
- Hans V Westerhoff
- Department of Molecular Cell Biology, Vrije Universiteit Amsterdam, A-Life, De Boelelaan 1085, 1081 HV, Amsterdam, the Netherlands; Synthetic Systems Biology and Nuclear Organization, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 XH, Amsterdam, the Netherlands; School of Biological Sciences, Medicine and Health, University of Manchester, Manchester, United Kingdom; Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch, 7600, South Africa.
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de Paz-Lugo P, Lupiáñez JA, Sicilia J, Meléndez-Hevia E. Control analysis of collagen synthesis by glycine, proline and lysine in bovine chondrocytes in vitro - Its relevance for medicine and nutrition. Biosystems 2023; 232:105004. [PMID: 37598999 DOI: 10.1016/j.biosystems.2023.105004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 08/08/2023] [Accepted: 08/17/2023] [Indexed: 08/22/2023]
Abstract
Collagen synthesis is severely diminished in osteoarthritis; thus, enhancing it may help the regeneration of cartilage. Collagen synthesis is submitted to a large procollagen cycle where the greater part of the newly synthesized protein is degraded inside the cell producing a huge waste of material and energy. We have applied the Metabolic Control Analysis approach to study the control of collagen synthesis flux by means of the response coefficients of the flux with respect to glycine, proline and lysine. Our results show that the main cause of the procollagen cycle is a protein misfolding mainly due to glycine scarcity, as well as a moderate deficiency of proline and lysine for collagen synthesis. Thus, increasing these amino acids in the diet (especially glycine) may well be a strategy for helping cartilage regeneration by enhancing collagen synthesis and reducing its huge waste in the procollagen cycle; this possibly contributes to the treatment and prevention of osteoarthritis.
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Affiliation(s)
- Patricia de Paz-Lugo
- Instituto del Metabolismo Celular, Calle Manuel de Falla nº15, La Laguna, 38208, Tenerife, Canary Islands, Spain.
| | - José Antonio Lupiáñez
- Universidad de Granada, Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias, Avda. Fuentenueva nº 1, 18071, Granada, Spain.
| | - Joaquín Sicilia
- Universidad de La Laguna, Departamento de Matemáticas, Estadística e Investigación Operativa, Avda. Astrofísico Francisco Sánchez, S/n. La Laguna, 38206, Tenerife, Canary Islands, Spain.
| | - Enrique Meléndez-Hevia
- Instituto del Metabolismo Celular, Calle Manuel de Falla nº15, La Laguna, 38208, Tenerife, Canary Islands, Spain.
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van Niekerk DD, Rust E, Bruggeman F, Westerhoff HV, Snoep JL. Is distance from equilibrium a good indicator for a reaction's flux control? Biosystems 2023; 232:104988. [PMID: 37541333 DOI: 10.1016/j.biosystems.2023.104988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Revised: 07/26/2023] [Accepted: 07/27/2023] [Indexed: 08/06/2023]
Abstract
By analysing a large set of models obtained from the JWS Online and Biomodels databases, we tested to what extent the disequilibrium ratio can be used as an estimator for the flux control of a reaction, a discussion point that was already raised by Kacser and Burns, and Heinrich and Rapoport in their seminal MCA manuscripts. Whereas no functional relation was observed, the disequilibrium ratio can be used as an estimator for the maximal flux control of a reaction step. We extended the original analysis of the relationship by incorporating the overall pathway disequilibrium ratio in the expression, which made it possible to make explicit expressions for flux control coefficients.
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Affiliation(s)
| | - Erik Rust
- Department of Biochemistry, Stellenbosch University, South Africa
| | - Frank Bruggeman
- Molecular Cell Biology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Hans V Westerhoff
- Molecular Cell Biology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands; Swammerdam Institute for Life Sciences, University of Amsterdam, Sciencepark 904, 1098 XH Amsterdam, The Netherlands; School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PT, UK; Stellenbosch Institute of Advanced Studies (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch 7600, South Africa
| | - Jacky L Snoep
- Department of Biochemistry, Stellenbosch University, South Africa; Molecular Cell Biology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
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Kouril T, October C, Hollocks S, Odendaal C, van Niekerk DD, Snoep JL. Inhibitor titrations reveal low control of glyceraldehyde 3-phosphate dehydrogenase and high control of hexokinase on glycolytic flux in an aggressive triple-negative breast cancer cell line. Biosystems 2023; 231:104969. [PMID: 37423593 DOI: 10.1016/j.biosystems.2023.104969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 07/11/2023]
Abstract
The glycolytic flux, and in particular lactate production, is strongly increased in cancer cells compared to normal cells, a characteristic often referred to as aerobic glycolysis or the Warburg effect. This makes the glycolytic pathway a potential drug target, in particular if the flux control distribution in the pathway has shifted due to the metabolic reprogramming in cancer cells. The flux response of a drug is dependent on both the sensitivity of the target to the drug and the flux control of the target, and both these characteristics can be exploited to obtain selectivity for cancer cells. Traditionally drug development programs have focused on selective sensitivity of the drug, not necessarily focussing on the flux control of the target. We determined the flux control of two steps that have been suggested to have high control in cancer cells, using two inhibitors, iodoacetic acid and 3-bromopyruvate, and measured a flux control of the glyceraldehyde 3-phosphate dehydrogenase close to zero, while the hexokinase holds 50% of all flux control in glycolysis in an invasive cancer cell line MDA-mb-231.
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Affiliation(s)
- Theresa Kouril
- Department of Biochemistry, Stellenbosch University, South Africa
| | - Craig October
- Department of Biochemistry, Stellenbosch University, South Africa
| | | | | | | | - Jacky L Snoep
- Department of Biochemistry, Stellenbosch University, South Africa; Molecular Cell Biology, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
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de Atauri P, Foguet C, Cascante M. Control analysis in the identification of key enzymes driving metabolic adaptations: Towards drug target discovery. Biosystems 2023; 231:104984. [PMID: 37506820 DOI: 10.1016/j.biosystems.2023.104984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 07/18/2023] [Accepted: 07/25/2023] [Indexed: 07/30/2023]
Abstract
Metabolic Control Analysis (MCA) marked a turning point in understanding the design principles of metabolic network control by establishing control coefficients as a means to quantify the degree of control that an enzyme exerts on flux or metabolite concentrations. MCA has demonstrated that control of metabolic pathways is distributed among many enzymes rather than depending on a single rate-limiting step. MCA also proved that this distribution depends not only on the stoichiometric structure of the network but also on other kinetic determinants, such as the degree of saturation of the enzyme active site, the distance to thermodynamic equilibrium, and metabolite feedback regulatory loops. Consequently, predicting the alterations that occur during metabolic adaptation in response to strong changes involving a redistribution in such control distribution can be challenging. Here, using the framework provided by MCA, we illustrate how control distribution in a metabolic pathway/network depends on enzyme kinetic determinants and to what extent the redistribution of control affects our predictions on candidate enzymes suitable as targets for small molecule inhibition in the drug discovery process. Our results uncover that kinetic determinants can lead to unexpected control distribution and outcomes that cannot be predicted solely from stoichiometric determinants. We also unveil that the inference of key enzyme-drivers of an observed metabolic adaptation can be dramatically improved using mean control coefficients and ruling out those enzyme activities that are associated with low control coefficients. As the use of constraint-based stoichiometric genome-scale metabolic models (GSMMs) becomes increasingly prevalent for identifying genes/enzymes that could be potential drug targets, we anticipate that incorporating kinetic determinants and ruling out enzymes with low control coefficients into GSMM workflows will facilitate more accurate predictions and reveal novel therapeutic targets.
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Affiliation(s)
- Pedro de Atauri
- Department of Biochemistry and Molecular Biomedicine & Institute of Biomedicine of Universitat de Barcelona, Faculty of Biology, Universitat de Barcelona, Barcelona, 08028, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III (ISCIII), Madrid, 28020, Spain.
| | - Carles Foguet
- British Heart Foundation Cardiovascular Epidemiology Unit and Victor Phillip Dahdaleh Heart and Lung Research Institute, University of Cambridge, Cambridge, CB2 0BD, United Kingdom
| | - Marta Cascante
- Department of Biochemistry and Molecular Biomedicine & Institute of Biomedicine of Universitat de Barcelona, Faculty of Biology, Universitat de Barcelona, Barcelona, 08028, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Instituto de Salud Carlos III (ISCIII), Madrid, 28020, Spain.
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Martin JP, Rasor BJ, DeBonis J, Karim AS, Jewett MC, Tyo KEJ, Broadbelt LJ. A dynamic kinetic model captures cell-free metabolism for improved butanol production. Metab Eng 2023; 76:133-145. [PMID: 36724840 DOI: 10.1016/j.ymben.2023.01.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 11/30/2022] [Accepted: 01/25/2023] [Indexed: 01/30/2023]
Abstract
Cell-free systems are useful tools for prototyping metabolic pathways and optimizing the production of various bioproducts. Mechanistically-based kinetic models are uniquely suited to analyze dynamic experimental data collected from cell-free systems and provide vital qualitative insight. However, to date, dynamic kinetic models have not been applied with rigorous biological constraints or trained on adequate experimental data to the degree that they would give high confidence in predictions and broadly demonstrate the potential for widespread use of such kinetic models. In this work, we construct a large-scale dynamic model of cell-free metabolism with the goal of understanding and optimizing butanol production in a cell-free system. Using a combination of parameterization methods, the resultant model captures experimental metabolite measurements across two experimental conditions for nine metabolites at timepoints between 0 and 24 h. We present analysis of the model predictions, provide recommendations for butanol optimization, and identify the aldehyde/alcohol dehydrogenase as the primary bottleneck in butanol production. Sensitivity analysis further reveals the extent to which various parameters are constrained, and our approach for probing valid parameter ranges can be applied to other modeling efforts.
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Affiliation(s)
- Jacob P Martin
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, 60208, USA
| | - Blake J Rasor
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, 60208, USA
| | - Jonathon DeBonis
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Ashty S Karim
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, 60208, USA
| | - Michael C Jewett
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, 60208, USA
| | - Keith E J Tyo
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA; Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, 60208, USA
| | - Linda J Broadbelt
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA.
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Schoppel K, Trachtmann N, Korzin EJ, Tzanavari A, Sprenger GA, Weuster-Botz D. Metabolic control analysis enables rational improvement of E. coli L-tryptophan producers but methylglyoxal formation limits glycerol-based production. Microb Cell Fact 2022; 21:201. [PMID: 36195869 PMCID: PMC9531422 DOI: 10.1186/s12934-022-01930-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 09/24/2022] [Indexed: 11/24/2022] Open
Abstract
Background Although efficient l-tryptophan production using engineered Escherichia coli is established from glucose, the use of alternative carbon sources is still very limited. Through the application of glycerol as an alternate, a more sustainable substrate (by-product of biodiesel preparation), the well-studied intracellular glycolytic pathways are rerouted, resulting in the activity of different intracellular control sites and regulations, which are not fully understood in detail. Metabolic analysis was applied to well-known engineered E. coli cells with 10 genetic modifications. Cells were withdrawn from a fed-batch production process with glycerol as a carbon source, followed by metabolic control analysis (MCA). This resulted in the identification of several additional enzymes controlling the carbon flux to l-tryptophan. Results These controlling enzyme activities were addressed stepwise by the targeted overexpression of 4 additional enzymes (trpC, trpB, serB, aroB). Their efficacy regarding l-tryptophan productivity was evaluated under consistent fed-batch cultivation conditions. Although process comparability was impeded by process variances related to a temporal, unpredictable break-off in l-tryptophan production, process improvements of up to 28% with respect to the l-tryptophan produced were observed using the new producer strains. The intracellular effects of these targeted genetic modifications were revealed by metabolic analysis in combination with MCA and expression analysis. Furthermore, it was discovered that the E. coli cells produced the highly toxic metabolite methylglyoxal (MGO) during the fed-batch process. A closer look at the MGO production and detoxification on the metabolome, fluxome, and transcriptome level of the engineered E. coli indicated that the highly toxic metabolite plays a critical role in the production of aromatic amino acids with glycerol as a carbon source. Conclusions A detailed process analysis of a new l-tryptophan producer strain revealed that several of the 4 targeted genetic modifications of the E. colil-tryptophan producer strain proved to be effective, and, for others, new engineering approaches could be derived from the results. As a starting point for further strain and process optimization, the up-regulation of MGO detoxifying enzymes and a lowering of the feeding rate during the last third of the cultivation seems reasonable. Supplementary Information The online version contains supplementary material available at 10.1186/s12934-022-01930-1.
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Affiliation(s)
- Kristin Schoppel
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching, Germany
| | - Natalia Trachtmann
- Institute of Microbiology, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Emil J Korzin
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching, Germany
| | - Angelina Tzanavari
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching, Germany
| | - Georg A Sprenger
- Institute of Microbiology, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Dirk Weuster-Botz
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstrasse 15, 85748, Garching, Germany.
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Schoppel K, Trachtmann N, Mittermeier F, Sprenger GA, Weuster-Botz D. Metabolic control analysis of L-tryptophan producing Escherichia coli applying targeted perturbation with shikimate. Bioprocess Biosyst Eng 2021; 44:2591-2613. [PMID: 34519841 PMCID: PMC8536597 DOI: 10.1007/s00449-021-02630-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 08/27/2021] [Indexed: 12/26/2022]
Abstract
L-tryptophan production from glycerol with Escherichia coli was analysed by perturbation studies and metabolic control analysis. The insertion of a non-natural shikimate transporter into the genome of an Escherichia coli L-tryptophan production strain enabled targeted perturbation within the product pathway with shikimate during parallelised short-term perturbation experiments with cells withdrawn from a 15 L fed-batch production process. Expression of the shikimate/H+-symporter gene (shiA) from Corynebacterium glutamicum did not alter process performance within the estimation error. Metabolic analyses and subsequent extensive data evaluation were performed based on the data of the parallel analysis reactors and the production process. Extracellular rates and intracellular metabolite concentrations displayed evident deflections in cell metabolism and particularly in chorismate biosynthesis due to the perturbations with shikimate. Intracellular flux distributions were estimated using a thermodynamics-based flux analysis method, which integrates thermodynamic constraints and intracellular metabolite concentrations to restrain the solution space. Feasible flux distributions, Gibbs reaction energies and concentration ranges were computed simultaneously for the genome-wide metabolic model, with minimum bias in relation to the direction of metabolic reactions. Metabolic control analysis was applied to estimate elasticities and flux control coefficients, predicting controlling sites for L-tryptophan biosynthesis. The addition of shikimate led to enhanced deviations in chorismate biosynthesis, revealing a so far not observed control of 3-dehydroquinate synthase on L-tryptophan formation. The relative expression of the identified target genes was analysed with RT-qPCR. Transcriptome analysis revealed disparities in gene expression and the localisation of target genes to further improve the microbial L-tryptophan producer by metabolic engineering.
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Affiliation(s)
- Kristin Schoppel
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstraße 15, 85748, Garching, Germany
| | - Natalia Trachtmann
- Institute of Microbiology, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Fabian Mittermeier
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstraße 15, 85748, Garching, Germany
| | - Georg A Sprenger
- Institute of Microbiology, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany
| | - Dirk Weuster-Botz
- Institute of Biochemical Engineering, Technical University of Munich, Boltzmannstraße 15, 85748, Garching, Germany.
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Shimizu H, Toya Y. Recent advances in metabolic engineering-integration of in silico design and experimental analysis of metabolic pathways. J Biosci Bioeng 2021; 132:429-436. [PMID: 34509367 DOI: 10.1016/j.jbiosc.2021.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/07/2021] [Indexed: 11/29/2022]
Abstract
Microorganisms are widely used to produce valuable compounds. Because thousands of metabolic reactions occur simultaneously and many metabolic reactions are related to target production and cell growth, the development of a rational design method for metabolic pathway modification to optimize target production is needed. In this paper, recent advances in metabolic engineering are reviewed, specifically considering computational pathway modification design and experimental evaluation of metabolic fluxes by 13C-metabolic flux analysis. Computational tools for seeking effective gene deletion targets and recruiting heterologous genes are described in flux balance analysis approaches. A kinetic model and adaptive laboratory evolution were applied to identify and eliminate the rate-limiting step in metabolic pathways. Data science-based approaches for process monitoring and control are described to maximize the performance of engineered cells in bioreactors.
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Affiliation(s)
- Hiroshi Shimizu
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Yoshihiro Toya
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan
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Hameri T, Fengos G, Hatzimanikatis V. The effects of model complexity and size on metabolic flux distribution and control: case study in Escherichia coli. BMC Bioinformatics 2021; 22:134. [PMID: 33743594 PMCID: PMC7981984 DOI: 10.1186/s12859-021-04066-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Accepted: 03/08/2021] [Indexed: 12/31/2022] Open
Abstract
Background Significant efforts have been made in building large-scale kinetic models of cellular metabolism in the past two decades. However, most kinetic models published to date, remain focused around central carbon pathways or are built around ad hoc reduced models without clear justification on their derivation and usage. Systematic algorithms exist for reducing genome-scale metabolic reconstructions to build thermodynamically feasible and consistently reduced stoichiometric models. However, it is important to study how network complexity affects conclusions derived from large-scale kinetic models built around consistently reduced models before we can apply them to study biological systems. Results We reduced the iJO1366 Escherichia Coli genome-scale metabolic reconstruction systematically to build three stoichiometric models of different size. Since the reduced models are expansions around the core subsystems for which the reduction was performed, the models are nested. We present a method for scaling up the flux profile and the concentration vector reference steady-states from the smallest model to the larger ones, whilst preserving maximum equivalency. Populations of kinetic models, preserving similarity in kinetic parameters, were built around the reference steady-states and their metabolic sensitivity coefficients (MSCs) were computed. The MSCs were sensitive to the model complexity. We proposed a metric for measuring the sensitivity of MSCs to these structural changes. Conclusions We proposed for the first time a workflow for scaling up the size of kinetic models while preserving equivalency between the kinetic models. Using this workflow, we demonstrate that model complexity in terms of networks size has significant impact on sensitivity characteristics of kinetic models. Therefore, it is essential to account for the effects of network complexity when constructing kinetic models. The presented metric for measuring MSC sensitivity to structural changes can guide modelers and experimentalists in improving model quality and guide synthetic biology and metabolic engineering. Our proposed workflow enables the testing of the suitability of a kinetic model for answering certain study-specific questions. We argue that the model-based metabolic design targets that are common across models of different size are of higher confidence, while those that are different could be the objective of investigations for model improvement. Supplementary Information The online version contains supplementary material available at 10.1186/s12859-021-04066-y.
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Affiliation(s)
- Tuure Hameri
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), 1015, Lausanne, Switzerland
| | - Georgios Fengos
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), 1015, Lausanne, Switzerland
| | - Vassily Hatzimanikatis
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), 1015, Lausanne, Switzerland.
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Kitamura S, Shimizu H, Toya Y. Identification of a rate-limiting step in a metabolic pathway using the kinetic model and in vitro experiment. J Biosci Bioeng 2020; 131:271-276. [PMID: 33168471 DOI: 10.1016/j.jbiosc.2020.10.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/19/2020] [Accepted: 10/22/2020] [Indexed: 11/16/2022]
Abstract
Identification of the rate-limiting step in a metabolic pathway is an important challenge in metabolic engineering for enhancing pathway flow. Although specific enzyme activities (Vmax) provide valuable clues for the identification, it is time-consuming and difficult to measure multiple enzymes in the pathway because different assay protocols are required for each enzyme. In the present study, we propose a method to simultaneously determine the Vmax values of multiple enzymes using a kinetic model with a time course of the intermediate concentrations through an in vitro experiment. To demonstrate this method, nine glycolysis reactions for converting glucose-6-phosphate (G6P) to pyruvate in Escherichia coli were considered. In a reaction mixture containing G6P and cofactors, glycolysis was initiated by adding a crude cell extract obtained from stationary phase cells. The Vmax values were optimized to minimize the difference between the measured and simulated time-courses using a kinetic model. Metabolic control analysis using the kinetic model with the estimated Vmax values revealed that fructose bisphosphate aldolase (FBA) was the rate-limiting step in the upper part of glycolysis. The addition of FBA in the reaction mixture successfully increased the glycolytic flux in vitro. Furthermore, in vivo, the specific glucose consumption rate of an FBA overexpression strain was 1.4 times higher than that of the control strain during the stationary phase. These results confirmed that FBA was the rate-limiting step in glycolysis under the stationary phase. This approach provides Vmax values of multiple enzymes in a pathway for metabolic control analysis with a kinetic model.
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Affiliation(s)
- Sayaka Kitamura
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Hiroshi Shimizu
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yoshihiro Toya
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
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16
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Harwood JL. Working with Randy: The Diacylglycerol Acyltransferase Story. Lipids 2020; 55:419-423. [PMID: 32701170 DOI: 10.1002/lipd.12267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 03/29/2020] [Accepted: 06/17/2020] [Indexed: 12/19/2022]
Abstract
Vegetable oils are one of the main agricultural commodities. Demand has been increasing steadily over the last five decades and, with finite land available, it is vital that we increase productivity. My laboratory has focused on the regulation of plant lipid metabolism and, as part of this work, we identified diacylglycerol acyltransferase (DGAT) as important at regulating carbon flux during oil accumulation. This led to collaborations with Randy Weselake's research group when we quantified the importance of DGAT in oilseed rape by using flux control analysis. Later, with David Taylor, we showed that over-expression of DGAT boosted oil accumulation in field-grown crops by around 8%. These studies led to a multitude of experiments with different oil crops, such as oil palm and soybean, as well as many rewarding collaborations with Randy.
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Affiliation(s)
- John L Harwood
- School of Biosciences, Cardiff University, Cardiff, CF10 3AX, Wales, UK
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17
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Abstract
To validate therapeutic targets in metabolic pathways of trypanosomatids, the criterion of enzyme essentiality determined by gene knockout or knockdown is usually being applied. Since, it is often found that most of the enzymes/proteins analyzed are essential, additional criteria have to be implemented for drug target prioritization. Metabolic control analysis (MCA), often in conjunction with kinetic pathway modeling, offers such possibility for prioritization. MCA is a theoretical and experimental approach to analyze how metabolic pathways are controlled. It involves strategies to perform quantitative analyses to determine the degree in which an enzyme controls a pathway flux, a value called flux control coefficient ([Formula: see text]). By determining the [Formula: see text] of individual steps in a metabolic pathway, the distribution of control of the pathway is established, that is, the identification of the main flux-controlling steps. Therefore, MCA can help in ranking pathway enzymes as drug targets from a metabolic perspective. In this chapter, three approaches to determine [Formula: see text] are reviewed: (1) In vitro pathway reconstitution, (2) manipulation of enzyme activities within parasites, and (3) in silico kinetic modeling of the metabolic pathway. To perform these methods, accurate experimental data of enzyme activities, metabolite concentrations and pathway fluxes are necessary. The methodology is illustrated with the example of trypanothione metabolism of Trypanosoma cruzi and protocols to determine such experimental data for this metabolic process are also described. However, the MCA strategy can be applied to any metabolic pathway in the parasite and general directions to perform it are provided in this chapter.
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Affiliation(s)
- Zabdi González-Chávez
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Ciudad de México, Mexico
| | - Citlali Vázquez
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Ciudad de México, Mexico
| | - Rafael Moreno-Sánchez
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Ciudad de México, Mexico
| | - Emma Saavedra
- Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chávez, Ciudad de México, Mexico.
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Volke DC, Rohwer J, Fischer R, Jennewein S. Investigation of the methylerythritol 4-phosphate pathway for microbial terpenoid production through metabolic control analysis. Microb Cell Fact 2019; 18:192. [PMID: 31690314 DOI: 10.1186/s12934-019-1235-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 10/17/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Terpenoids are of high interest as chemical building blocks and pharmaceuticals. In microbes, terpenoids can be synthesized via the methylerythritol phosphate (MEP) or mevalonate (MVA) pathways. Although the MEP pathway has a higher theoretical yield, metabolic engineering has met with little success because the regulation of the pathway is poorly understood. RESULTS We applied metabolic control analysis to the MEP pathway in Escherichia coli expressing a heterologous isoprene synthase gene (ispS). The expression of ispS led to the accumulation of isopentenyl pyrophosphate (IPP)/dimethylallyl pyrophosphate (DMAPP) and severely impaired bacterial growth, but the coexpression of ispS and isopentenyl diphosphate isomerase (idi) restored normal growth and wild-type IPP/DMAPP levels. Targeted proteomics and metabolomics analysis provided a quantitative description of the pathway, which was perturbed by randomizing the ribosome binding site in the gene encoding 1-deoxyxylulose 5-phosphate synthase (Dxs). Dxs has a flux control coefficient of 0.35 (i.e., a 1% increase in Dxs activity resulted in a 0.35% increase in pathway flux) in the isoprene-producing strain and therefore exerted significant control over the flux though the MEP pathway. At higher dxs expression levels, the intracellular concentration of 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEcPP) increased substantially in contrast to the other MEP pathway intermediates, which were linearly dependent on the abundance of Dxs. This indicates that 4-hydroxy-3-methylbut-2-en-1-yl diphosphate synthase (IspG), which consumes MEcPP, became saturated and therefore limited the flux towards isoprene. The higher intracellular concentrations of MEcPP led to the efflux of this intermediate into the growth medium. DISCUSSION These findings show the importance of Dxs, Idi and IspG and metabolite export for metabolic engineering of the MEP pathway and will facilitate further approaches for the microbial production of valuable isoprenoids.
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Tröndle J, Schoppel K, Bleidt A, Trachtmann N, Sprenger GA, Weuster-Botz D. Metabolic control analysis of L-tryptophan production with Escherichia coli based on data from short-term perturbation experiments. J Biotechnol 2019; 307:15-28. [PMID: 31639341 DOI: 10.1016/j.jbiotec.2019.10.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2019] [Accepted: 10/10/2019] [Indexed: 12/21/2022]
Abstract
E. coli strain NT1259 /pF112aroFBLkan was able to produce 14.3 g L-1 L-tryptophan within 68 h in a fed-batch process from glycerol on a 15 L scale. To gain detailed insight into metabolism of this E. coli strain in the fed-batch process, a sample of L-tryptophan producing cells was withdrawn after 47 h, was separated rapidly and then resuspended in four parallel stirred-tank bioreactors with fresh media. Four different carbon sources (glucose, glycerol, succinate, pyruvate) were supplied individually with varying feeding rates within 19 min and the metabolic reactions of the cells in the four parallel reactors were analyzed by quantification of extracellular and intracellular substrate, product and metabolite concentrations. Data analysis allowed the estimation of intracellular carbon fluxes and of thermodynamic limitations concerning intracellular concentrations and reaction energies. Carbon fluxes and intracellular metabolite concentrations enabled the estimation of elasticities and flux control coefficients by applying metabolic control analysis making use of a metabolic model considering 48 enzymatic reactions and 56 metabolites. As the flux control coefficients describe connections between enzyme activities and metabolic fluxes, they reveal genetic targets for strain improvement. Metabolic control analysis of the recombinant E. coli cells withdrawn from the fed-batch production process clearly indicated that (i) the supply of two precursors for L-tryptophan biosynthesis, L-serine and phosphoribosyl-pyrophosphate, as well as (ii) the formation of aromatic byproducts and (iii) the enzymatic steps of igps and trps2 within the L-tryptophan biosynthesis pathway have major impact on fed-batch production of L-tryptophan from glycerol and should be the targets for further strain improvements.
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Affiliation(s)
- Julia Tröndle
- Technical University of Munich, Institute of Biochemical Engineering, Boltzmannstr. 15, 85748, Garching, Germany
| | - Kristin Schoppel
- Technical University of Munich, Institute of Biochemical Engineering, Boltzmannstr. 15, 85748, Garching, Germany
| | - Arne Bleidt
- Technical University of Munich, Institute of Biochemical Engineering, Boltzmannstr. 15, 85748, Garching, Germany
| | - Natalia Trachtmann
- University of Stuttgart, Institute of Microbiology, Allmandring 31, 70569, Stuttgart, Germany
| | - Georg A Sprenger
- University of Stuttgart, Institute of Microbiology, Allmandring 31, 70569, Stuttgart, Germany
| | - Dirk Weuster-Botz
- Technical University of Munich, Institute of Biochemical Engineering, Boltzmannstr. 15, 85748, Garching, Germany.
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20
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Meshram RJ, Goundge MB, Kolte BS, Gacche RN. An in silico approach in identification of drug targets in Leishmania: A subtractive genomic and metabolic simulation analysis. Parasitol Int 2018; 69:59-70. [PMID: 30503238 DOI: 10.1016/j.parint.2018.11.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 10/17/2018] [Accepted: 11/28/2018] [Indexed: 12/26/2022]
Abstract
Leishmaniasis is one of the major health issue in developing countries. The current therapeutic regimen for this disease is less effective with lot of adverse effects thereby warranting an urgent need to develop not only new and selective drug candidates but also identification of effective drug targets. Here we present subtractive genomics procedure for identification of putative drug targets in Leishmania. Comprehensive druggability analysis has been carried out in the current work for identified metabolic pathways and drug targets. We also demonstrate effective metabolic simulation methodology to pinpoint putative drug targets in threonine biosynthesis pathway. Metabolic simulation data from the current study indicate that decreasing flux through homoserine kinase reaction can be considered as a good therapeutic opportunity. The data from current study is expected to show new avenue for designing experimental strategies in search of anti-leishmanial agents.
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Affiliation(s)
- Rohan J Meshram
- Bioinformatics Centre, Savitribai Phule Pune University, Pune 411007, India.
| | - Mayuri B Goundge
- Bioinformatics Centre, Savitribai Phule Pune University, Pune 411007, India
| | - Baban S Kolte
- Bioinformatics Centre, Savitribai Phule Pune University, Pune 411007, India; Department of Biotechnology, Savitribai Phule Pune University, Pune 411007, India
| | - Rajesh N Gacche
- Department of Biotechnology, Savitribai Phule Pune University, Pune 411007, India
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21
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Gerencser AA. Metabolic activation-driven mitochondrial hyperpolarization predicts insulin secretion in human pancreatic beta-cells. Biochim Biophys Acta Bioenerg 2018; 1859:817-828. [PMID: 29886047 DOI: 10.1016/j.bbabio.2018.06.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/18/2018] [Accepted: 06/05/2018] [Indexed: 12/31/2022]
Abstract
Mitochondrial metabolism plays a central role in insulin secretion in pancreatic beta-cells. Generation of protonmotive force and ATP synthesis from glucose-originated pyruvate are critical steps in the canonical pathway of glucose-stimulated insulin secretion. Mitochondrial metabolism is intertwined with pathways that are thought to amplify insulin secretion with mechanisms distinct from the canonical pathway, and the relative importance of these two pathways is controversial. Here I show that glucose-induced mitochondrial membrane potential (MMP) hyperpolarization is necessary for, and predicts, the rate of insulin secretion in primary cultured human beta-cells. When glucose concentration is elevated, increased metabolism results in a substantial MMP hyperpolarization, as well as in increased rates of ATP synthesis and turnover marked by faster cell respiration. Using modular kinetic analysis I explored what properties of cellular energy metabolism enable a large glucose-induced change in MMP in human beta-cells. I found that an ATP-dependent pathway activates glucose or substrate oxidation, acting as a positive feedback in energy metabolism. This activation mechanism is essential for concomitant fast respiration and high MMP, and for a high magnitude glucose-induced MMP hyperpolarization and therefore for insulin secretion.
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Affiliation(s)
- Akos A Gerencser
- Buck Institute for Research on Aging, 8001 Redwood Blvd, Novato, CA 94945, United States; Image Analyst Software, 43 Nova Lane, Novato, CA 94945, United States.
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22
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Saa PA, Nielsen LK. Formulation, construction and analysis of kinetic models of metabolism: A review of modelling frameworks. Biotechnol Adv 2017; 35:981-1003. [PMID: 28916392 DOI: 10.1016/j.biotechadv.2017.09.005] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 08/30/2017] [Accepted: 09/10/2017] [Indexed: 12/13/2022]
Abstract
Kinetic models are critical to predict the dynamic behaviour of metabolic networks. Mechanistic kinetic models for large networks remain uncommon due to the difficulty of fitting their parameters. Recent modelling frameworks promise new ways to overcome this obstacle while retaining predictive capabilities. In this review, we present an overview of the relevant mathematical frameworks for kinetic formulation, construction and analysis. Starting with kinetic formalisms, we next review statistical methods for parameter inference, as well as recent computational frameworks applied to the construction and analysis of kinetic models. Finally, we discuss opportunities and limitations hindering the development of larger kinetic reconstructions.
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23
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Ivanina AV, Nesmelova I, Leamy L, Sokolov EP, Sokolova IM. Intermittent hypoxia leads to functional reorganization of mitochondria and affects cellular bioenergetics in marine molluscs. ACTA ACUST UNITED AC 2017; 219:1659-74. [PMID: 27252455 DOI: 10.1242/jeb.134700] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Accepted: 03/14/2016] [Indexed: 12/11/2022]
Abstract
Fluctuations in oxygen (O2) concentrations represent a major challenge to aerobic organisms and can be extremely damaging to their mitochondria. Marine intertidal molluscs are well-adapted to frequent O2 fluctuations, yet it remains unknown how their mitochondrial functions are regulated to sustain energy metabolism and prevent cellular damage during hypoxia and reoxygenation (H/R). We used metabolic control analysis to investigate the mechanisms of mitochondrial responses to H/R stress (18 h at <0.1% O2 followed by 1 h of reoxygenation) using hypoxia-tolerant intertidal clams Mercenaria mercenaria and hypoxia-sensitive subtidal scallops Argopecten irradians as models. We also assessed H/R-induced changes in cellular energy balance, oxidative damage and unfolded protein response to determine the potential links between mitochondrial dysfunction and cellular injury. Mitochondrial responses to H/R in scallops strongly resembled those in other hypoxia-sensitive organisms. Exposure to hypoxia followed by reoxygenation led to a strong decrease in the substrate oxidation (SOX) and phosphorylation (PHOS) capacities as well as partial depolarization of mitochondria of scallops. Elevated mRNA expression of a reactive oxygen species-sensitive enzyme aconitase and Lon protease (responsible for degradation of oxidized mitochondrial proteins) during H/R stress was consistent with elevated levels of oxidative stress in mitochondria of scallops. In hypoxia-tolerant clams, mitochondrial SOX capacity was enhanced during hypoxia and continued rising during the first hour of reoxygenation. In both species, the mitochondrial PHOS capacity was suppressed during hypoxia, likely to prevent ATP wastage by the reverse action of FO,F1-ATPase. The PHOS capacity recovered after 1 h of reoxygenation in clams but not in scallops. Compared with scallops, clams showed a greater suppression of energy-consuming processes (such as protein turnover and ion transport) during hypoxia, indicated by inactivation of the translation initiation factor EIF-2α, suppression of 26S proteasome activity and a dramatic decrease in the activity of Na(+)/K(+)-ATPase. The steady-state levels of adenylates were preserved during H/R exposure and AMP-dependent protein kinase was not activated in either species, indicating that the H/R exposure did not lead to severe energy deficiency. Taken together, our findings suggest that mitochondrial reorganizations sustaining high oxidative phosphorylation flux during recovery, combined with the ability to suppress ATP-demanding cellular functions during hypoxia, may contribute to high resilience of clams to H/R stress and help maintain energy homeostasis during frequent H/R cycles in the intertidal zone.
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Affiliation(s)
- Anna V Ivanina
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Irina Nesmelova
- Department of Physics, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Larry Leamy
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
| | - Eugene P Sokolov
- Department of General Surgery, Carolinas Medical Center, Charlotte, NC 28232, USA
| | - Inna M Sokolova
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223, USA
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24
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Miskovic L, Alff-Tuomala S, Soh KC, Barth D, Salusjärvi L, Pitkänen JP, Ruohonen L, Penttilä M, Hatzimanikatis V. A design-build-test cycle using modeling and experiments reveals interdependencies between upper glycolysis and xylose uptake in recombinant S. cerevisiae and improves predictive capabilities of large-scale kinetic models. Biotechnol Biofuels 2017; 10:166. [PMID: 28674555 PMCID: PMC5485749 DOI: 10.1186/s13068-017-0838-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 06/06/2017] [Indexed: 05/28/2023]
Abstract
BACKGROUND Recent advancements in omics measurement technologies have led to an ever-increasing amount of available experimental data that necessitate systems-oriented methodologies for efficient and systematic integration of data into consistent large-scale kinetic models. These models can help us to uncover new insights into cellular physiology and also to assist in the rational design of bioreactor or fermentation processes. Optimization and Risk Analysis of Complex Living Entities (ORACLE) framework for the construction of large-scale kinetic models can be used as guidance for formulating alternative metabolic engineering strategies. RESULTS We used ORACLE in a metabolic engineering problem: improvement of the xylose uptake rate during mixed glucose-xylose consumption in a recombinant Saccharomyces cerevisiae strain. Using the data from bioreactor fermentations, we characterized network flux and concentration profiles representing possible physiological states of the analyzed strain. We then identified enzymes that could lead to improved flux through xylose transporters (XTR). For some of the identified enzymes, including hexokinase (HXK), we could not deduce if their control over XTR was positive or negative. We thus performed a follow-up experiment, and we found out that HXK2 deletion improves xylose uptake rate. The data from the performed experiments were then used to prune the kinetic models, and the predictions of the pruned population of kinetic models were in agreement with the experimental data collected on the HXK2-deficient S. cerevisiae strain. CONCLUSIONS We present a design-build-test cycle composed of modeling efforts and experiments with a glucose-xylose co-utilizing recombinant S. cerevisiae and its HXK2-deficient mutant that allowed us to uncover interdependencies between upper glycolysis and xylose uptake pathway. Through this cycle, we also obtained kinetic models with improved prediction capabilities. The present study demonstrates the potential of integrated "modeling and experiments" systems biology approaches that can be applied for diverse applications ranging from biotechnology to drug discovery.
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Affiliation(s)
- Ljubisa Miskovic
- Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | | | - Keng Cher Soh
- Ecole Polytechnique Federale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Dorothee Barth
- VTT Technical Research Centre of Finland Ltd, Espoo, Finland
| | | | | | - Laura Ruohonen
- VTT Technical Research Centre of Finland Ltd, Espoo, Finland
| | - Merja Penttilä
- VTT Technical Research Centre of Finland Ltd, Espoo, Finland
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25
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Teleki A, Rahnert M, Bungart O, Gann B, Ochrombel I, Takors R. Robust identification of metabolic control for microbial l-methionine production following an easy-to-use puristic approach. Metab Eng 2017; 41:159-172. [PMID: 28389396 DOI: 10.1016/j.ymben.2017.03.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 02/15/2017] [Accepted: 03/31/2017] [Indexed: 11/28/2022]
Abstract
The identification of promising metabolic engineering targets is a key issue in metabolic control analysis (MCA). Conventional approaches make intensive use of model-based studies, such as exploiting post-pulse metabolic dynamics after proper perturbation of the microbial system. Here, we present an easy-to-use, purely data-driven approach, defining pool efflux capacities (PEC) for identifying reactions that exert the highest flux control in linear pathways. Comparisons with linlog-based MCA and data-driven substrate elasticities (DDSE) showed that similar key control steps were identified using PEC. Using the example of l-methionine production with recombinant Escherichia coli, PEC consistently and robustly identified main flux controls using perturbation data after a non-labeled 12C-l-serine stimulus. Furthermore, the application of full-labeled 13C-l-serine stimuli yielded additional insights into stimulus propagation to l-methionine. PEC analysis performed on the 13C data set revealed the same targets as the 12C data set. Notably, the typical drawback of metabolome analysis, namely, the omnipresent leakage of metabolites, was excluded using the 13C PEC approach.
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Affiliation(s)
- A Teleki
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
| | - M Rahnert
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
| | - O Bungart
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
| | - B Gann
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
| | - I Ochrombel
- Evonik Nutrition & Care GmbH, Kantstr. 2, 33790 Halle, Germany
| | - R Takors
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany.
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Andreozzi S, Chakrabarti A, Soh KC, Burgard A, Yang TH, Van Dien S, Miskovic L, Hatzimanikatis V. Identification of metabolic engineering targets for the enhancement of 1,4-butanediol production in recombinant E. coli using large-scale kinetic models. Metab Eng 2016; 35:148-159. [PMID: 26855240 DOI: 10.1016/j.ymben.2016.01.009] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Revised: 12/16/2015] [Accepted: 01/29/2016] [Indexed: 11/24/2022]
Abstract
Rational metabolic engineering methods are increasingly employed in designing the commercially viable processes for the production of chemicals relevant to pharmaceutical, biotechnology, and food and beverage industries. With the growing availability of omics data and of methodologies capable to integrate the available data into models, mathematical modeling and computational analysis are becoming important in designing recombinant cellular organisms and optimizing cell performance with respect to desired criteria. In this contribution, we used the computational framework ORACLE (Optimization and Risk Analysis of Complex Living Entities) to analyze the physiology of recombinant Escherichia coli producing 1,4-butanediol (BDO) and to identify potential strategies for improved production of BDO. The framework allowed us to integrate data across multiple levels and to construct a population of large-scale kinetic models despite the lack of available information about kinetic properties of every enzyme in the metabolic pathways. We analyzed these models and we found that the enzymes that primarily control the fluxes leading to BDO production are part of central glycolysis, the lower branch of tricarboxylic acid (TCA) cycle and the novel BDO production route. Interestingly, among the enzymes between the glucose uptake and the BDO pathway, the enzymes belonging to the lower branch of TCA cycle have been identified as the most important for improving BDO production and yield. We also quantified the effects of changes of the target enzymes on other intracellular states like energy charge, cofactor levels, redox state, cellular growth, and byproduct formation. Independent earlier experiments on this strain confirmed that the computationally obtained conclusions are consistent with the experimentally tested designs, and the findings of the present studies can provide guidance for future work on strain improvement. Overall, these studies demonstrate the potential and effectiveness of ORACLE for the accelerated design of microbial cell factories.
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Affiliation(s)
- Stefano Andreozzi
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Anirikh Chakrabarti
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Keng Cher Soh
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | | | | | | | - Ljubisa Miskovic
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
| | - Vassily Hatzimanikatis
- Laboratory of Computational Systems Biotechnology (LCSB), Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland; Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland.
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Trausinger G, Gruber C, Krahulec S, Magnes C, Nidetzky B, Klimacek M. Identification of novel metabolic interactions controlling carbon flux from xylose to ethanol in natural and recombinant yeasts. Biotechnol Biofuels 2015; 8:157. [PMID: 26413156 PMCID: PMC4582818 DOI: 10.1186/s13068-015-0340-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 09/09/2015] [Indexed: 05/31/2023]
Abstract
BACKGROUND Unlike xylose-converting natural yeasts, recombinant strains of Saccharomyces cerevisiae expressing the same xylose assimilation pathway produce under anaerobic conditions xylitol rather than ethanol from xylose at low specific xylose conversion rates. Despite intense research efforts over the last two decades, differences in these phenotypes cannot be explained by current metabolic and kinetic models. To improve our understanding how metabolic flux of xylose carbon to ethanol is controlled, we developed a novel kinetic model based on enzyme mechanisms and applied quantitative metabolite profiling together with enzyme activity analysis to study xylose-to-ethanol metabolisms of Candida tenuis CBS4435 (q xylose = 0.10 g/gdc/h, 25 °C; Y ethanol = 0.44 g/g; Y xylitol = 0.09 g/g) and the recombinant S. cerevisiae strain BP000 (q xylose = 0.07 g/gdc/h, 30 °C; Y ethanol = 0.24 g/g; Y xylitol = 0.43 g/g), both expressing the same xylose reductase (XR), comprehensively. RESULTS Results from strain-to-strain metabolic control analysis indicated that activity levels of XR and the maximal flux capacity of the upper glycolysis (UG; both ≥ tenfold higher in CBS4435) contributed predominantly to phenotype differentiation while reactions from the oxidative pentose phosphate pathway played minor roles. Intracellular metabolite profiles supported results obtained from kinetic modeling and indicated a positive correlation between pool sizes of UG metabolites and carbon flux through the UG. For CBS4435, fast carbon flux through the UG could be associated with an allosteric control of 6-phosphofructokinase (PFK) activity by fructose 6-phosphate. The ability of CBS4435 to keep UG metabolites at high levels could be explained by low glycerol 3-phosphate phosphatase (GPP, 17-fold lower in CBS4435) and high XR activities. CONCLUSIONS By applying a systems biology approach in which we combined results obtained from metabolic control analysis based on kinetic modeling with data obtained from quantitative metabolite profiling and enzyme activity analyses, we could provide new insights into metabolic and kinetic interactions contributing to the control of carbon flux from xylose to ethanol. Supported by evidences presented two new targets, PFK and GPP, could be identified that aside from XR play pivotal roles in phenotype differentiation. Design of efficient and fast microbial ethanol producers in the future can certainly benefit from results presented in this study.
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Affiliation(s)
- Gert Trausinger
- />Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Petersgasse 12/1, 8010 Graz, Austria
- />HEALTH-Institute for Biomedicine and Health Sciences, Joanneum Research Forschungsgesellschaft m.b.H., Graz, Austria
| | - Christoph Gruber
- />Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Petersgasse 12/1, 8010 Graz, Austria
| | - Stefan Krahulec
- />Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Petersgasse 12/1, 8010 Graz, Austria
| | - Christoph Magnes
- />HEALTH-Institute for Biomedicine and Health Sciences, Joanneum Research Forschungsgesellschaft m.b.H., Graz, Austria
| | - Bernd Nidetzky
- />Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Petersgasse 12/1, 8010 Graz, Austria
| | - Mario Klimacek
- />Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, NAWI Graz, Petersgasse 12/1, 8010 Graz, Austria
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Ke W, Chang S, Chen X, Luo S, Jiang S, Yang P, Wu X, Zheng Z. Metabolic control analysis of L-lactate synthesis pathway in Rhizopus oryzae As 3.2686. Bioprocess Biosyst Eng 2015; 38:2189-99. [PMID: 26288952 DOI: 10.1007/s00449-015-1458-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 08/08/2015] [Indexed: 10/23/2022]
Abstract
The relationship between the metabolic flux and the activities of the pyruvate branching enzymes of Rhizopus oryzae As 3.2686 during L-lactate fermentation was investigated using the perturbation method of aeration. The control coefficients for five enzymes, pyruvate dehydrogenase (PDH), pyruvate carboxylase (PC), pyruvate decarboxylase (PDC), lactate dehydrogenase (LDH), and alcohol dehydrogenase (ADH), were calculated. Our results indicated significant correlations between PDH and PC, PDC and LDH, PDC and ADH, LDH and ADH, and PDC and PC. It also appeared that PDH, PC, and LDH strongly controlled the L-lactate flux; PDH and ADH strongly controlled the ethanol flux; while PDH and PC strongly controlled the acetyl coenzyme A flux and the oxaloacetate flux. Further, the flux control coefficient curves indicated that the control of the system gradually transferred from PDC to PC during the steady state. Therefore, PC was the key rate-limiting enzyme that controls the flux distribution.
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Affiliation(s)
- Wei Ke
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Shu Chang
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Xiaoju Chen
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Shuizhong Luo
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China.,Key Laboratory for Agricultural Products Processing of Anhui Province, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Shaotong Jiang
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China.,Key Laboratory for Agricultural Products Processing of Anhui Province, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Peizhou Yang
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China.,Key Laboratory for Agricultural Products Processing of Anhui Province, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Xuefeng Wu
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China.,Key Laboratory for Agricultural Products Processing of Anhui Province, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China
| | - Zhi Zheng
- School of Biotechnology and Food Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China. .,Key Laboratory for Agricultural Products Processing of Anhui Province, Hefei University of Technology, 193 Tunxi Road, Hefei, 230009, People's Republic of China.
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Kaldma A, Klepinin A, Chekulayev V, Mado K, Shevchuk I, Timohhina N, Tepp K, Kandashvili M, Varikmaa M, Koit A, Planken M, Heck K, Truu L, Planken A, Valvere V, Rebane E, Kaambre T. An in situ study of bioenergetic properties of human colorectal cancer: the regulation of mitochondrial respiration and distribution of flux control among the components of ATP synthasome. Int J Biochem Cell Biol 2014; 55:171-86. [PMID: 25218857 DOI: 10.1016/j.biocel.2014.09.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 08/12/2014] [Accepted: 09/02/2014] [Indexed: 11/25/2022]
Abstract
The aim of this study is to characterize the function of mitochondria and main energy fluxes in human colorectal cancer (HCC) cells. We have performed quantitative analysis of cellular respiration in post-operative tissue samples collected from 42 cancer patients. Permeabilized tumor tissue in combination with high resolution respirometry was used. Our results indicate that HCC is not a pure glycolytic tumor and the oxidative phosphorylation (OXPHOS) system may be the main provider of ATP in these tumor cells. The apparent Michaelis-Menten constant (Km) for ADP and maximal respiratory rate (Vm) values were calculated for the characterization of the affinity of mitochondria for exogenous ADP: normal colon tissue displayed low affinity (Km = 260 ± 55 μM) whereas the affinity of tumor mitochondria was significantly higher (Km = 126 ± 17 μM). But concurrently the Vm value of the tumor samples was 60-80% higher than that in control tissue. The reason for this change is related to the increased number of mitochondria. Our data suggest that in both HCC and normal intestinal cells tubulin β-II isoform probably does not play a role in the regulation of permeability of the MOM for adenine nucleotides. The mitochondrial creatine kinase energy transfer system is not functional in HCC and our experiments showed that adenylate kinase reactions could play an important role in the maintenance of energy homeostasis in colorectal carcinomas instead of creatine kinase. Immunofluorescent studies showed that hexokinase 2 (HK-2) was associated with mitochondria in HCC cells, but during carcinogenesis the total activity of HK did not change. Furthermore, only minor alterations in the expression of HK-1 and HK-2 isoforms have been observed. Metabolic Control analysis showed that the distribution of the control over electron transport chain and ATP synthasome complexes seemed to be similar in both tumor and control tissues. High flux control coefficients point to the possibility that the mitochondrial respiratory chain is reorganized in some way or assembled into large supercomplexes in both tissues.
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Affiliation(s)
- Andrus Kaldma
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Aleksandr Klepinin
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Vladimir Chekulayev
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Kati Mado
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Igor Shevchuk
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Natalja Timohhina
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Kersti Tepp
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | | | - Minna Varikmaa
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | - Andre Koit
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia
| | | | | | - Laura Truu
- Tallinn University of Technology, Tallinn, Estonia
| | - Anu Planken
- Cancer Research Competence Center, Tallinn, Estonia
| | | | - Egle Rebane
- Cancer Research Competence Center, Tallinn, Estonia
| | - Tuuli Kaambre
- Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia; Tallinn University, Tallinn, Estonia.
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30
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Guschina IA, Everard JD, Kinney AJ, Quant PA, Harwood JL. Studies on the regulation of lipid biosynthesis in plants: application of control analysis to soybean. Biochim Biophys Acta 2014; 1838:1488-500. [PMID: 24565795 DOI: 10.1016/j.bbamem.2014.02.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Revised: 02/03/2014] [Accepted: 02/11/2014] [Indexed: 01/13/2023]
Abstract
Although there is much knowledge of the enzymology (and genes coding the proteins) of lipid biosynthesis in higher plants, relatively little attention has been paid to regulation. We have demonstrated the important role for cholinephosphate cytidylyltransferase in the biosynthesis of the major extra-plastidic membrane lipid, phosphatidylcholine. We followed this work by applying control analysis to light-induced fatty acid synthesis. This was the first such application to lipid synthesis in any organism. The data showed that acetyl-CoA carboxylase was very important, exerting about half of the total control. We then applied metabolic control analysis to lipid accumulation in important oil crops - oilpalm, olive, and rapeseed. Recent data with soybean show that the block of fatty acid biosynthesis reactions exerts somewhat more control (63%) than lipid assembly although both are clearly very important. These results suggest that gene stacks, targeting both parts of the overall lipid synthesis pathway will be needed to increase significantly oil yields in soybean. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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Affiliation(s)
| | - John D Everard
- DuPont Agricultural Biotechnology, P.O. Box 80353, Wilmington, DE 19880, USA
| | - Anthony J Kinney
- DuPont Agricultural Biotechnology, P.O. Box 80353, Wilmington, DE 19880, USA
| | - Patti A Quant
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - John L Harwood
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK.
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31
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Varikmaa M, Bagur R, Kaambre T, Grichine A, Timohhina N, Tepp K, Shevchuk I, Chekulayev V, Metsis M, Boucher F, Saks V, Kuznetsov AV, Guzun R. Role of mitochondria-cytoskeleton interactions in respiration regulation and mitochondrial organization in striated muscles. Biochim Biophys Acta 2014; 1837:232-45. [PMID: 24189374 DOI: 10.1016/j.bbabio.2013.10.011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Revised: 09/28/2013] [Accepted: 10/28/2013] [Indexed: 01/08/2023]
Abstract
The aim of this work was to study the regulation of respiration and energy fluxes in permeabilized oxidative and glycolytic skeletal muscle fibers, focusing also on the role of cytoskeletal protein tubulin βII isotype in mitochondrial metabolism and organization. By analyzing accessibility of mitochondrial ADP, using respirometry and pyruvate kinase-phosphoenolpyruvate trapping system for ADP, we show that the apparent affinity of respiration for ADP can be directly linked to the permeability of the mitochondrial outer membrane (MOM). Previous studies have shown that MOM permeability in cardiomyocytes can be regulated by VDAC interaction with cytoskeletal protein, βII tubulin. We found that in oxidative soleus skeletal muscle the high apparent Km for ADP is associated with low MOM permeability and high expression of non-polymerized βII tubulin. Very low expression of non-polymerized form of βII tubulin in glycolytic muscles is associated with high MOM permeability for adenine nucleotides (low apparent Km for ADP).
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32
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Preller A, Wilson CAM, Quiroga-Roger D, Ureta T. Hexokinase and not glycogen synthase controls the flux through the glycogen synthesis pathway in frog oocytes. FEBS Lett 2013; 587:2825-31. [PMID: 23831065 DOI: 10.1016/j.febslet.2013.06.037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 06/20/2013] [Accepted: 06/21/2013] [Indexed: 10/26/2022]
Abstract
Here we set out to evaluate the role of hexokinase and glycogen synthase in the control of glycogen synthesis in vivo. We used metabolic control analysis (MCA) to determine the flux control coefficient for each of the enzymes involved in the pathway. Acute microinjection experiments in frog oocytes were specifically designed to change the endogenous activities of the enzymes, either by directly injecting increasing amounts of a given enzyme (HK, PGM and UGPase) or by microinjection of a positive allosteric effector (glc-6P for GS). Values of 0.61 ± 0.07, 0.19 ± 0.03, 0.13 ± 0.03, and -0.06 ± 0.08 were obtained for the flux control coefficients of hexokinase EC 2.7.1.1 (HK), phosphoglucomutase EC 5.4.2.1 (PGM), UDPglucose pyrophosphorylase EC 2.7.7.9 (UGPase) and glycogen synthase EC 2.4.1.11 (GS), respectively. These values satisfy the summation theorem since the sum of the control coefficients for all the enzymes of the pathway is 0.87. The results show that, in frog oocytes, glycogen synthesis through the direct pathway is under the control of hexokinase. Phosphoglucomutase and UDPG-pyrophosphorylase have a modest influence, while the control exerted by glycogen synthase is null.
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Affiliation(s)
- Ana Preller
- Department of Biology, Faculty of Sciences, University of Chile, Las Palmeras 3425, Ñuñoa, Santiago, Chile.
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Singh VK, Ghosh I. Methylerythritol phosphate pathway to isoprenoids: kinetic modeling and in silico enzyme inhibitions in Plasmodium falciparum. FEBS Lett 2013; 587:2806-17. [PMID: 23816706 DOI: 10.1016/j.febslet.2013.06.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 06/14/2013] [Accepted: 06/17/2013] [Indexed: 11/19/2022]
Abstract
The methylerythritol phosphate (MEP) pathway of Plasmodium falciparum (P. falciparum) has become an attractive target for anti-malarial drug discovery. This study describes a kinetic model of this pathway, its use in validating 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) as drug target from the systemic perspective, and additional target identification, using metabolic control analysis and in silico inhibition studies. In addition to DXR, 1-deoxy-d-xylulose 5-phosphate synthase (DXS) can be targeted because it is the first enzyme of the pathway and has the highest flux control coefficient followed by that of DXR. In silico inhibition of both enzymes caused large decrement in the pathway flux. An added advantage of targeting DXS is its influence on vitamin B1 and B6 biosynthesis. Two more potential targets, 2-C-methyl-d-erythritol 2,4-cyclodiphosphate synthase and 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase, were also identified. Their inhibition caused large accumulation of their substrates causing instability of the system. This study demonstrates that both types of enzyme targets, one acting via flux reduction and the other by metabolite accumulation, exist in P. falciparum MEP pathway. These groups of targets can be exploited for independent anti-malarial drugs.
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Affiliation(s)
- Vivek Kumar Singh
- School of Computational & Integrative Sciences, Jawaharlal Nehru University, New Delhi, India.
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Abstract
Modulation of metabolic fluxes in plants is usually not a successful business. The main reason is our limited understanding of metabolic plasticity and metabolic control, with the latter still largely influenced by the idea that each pathway has a rate limiting step controlling the flux. Not only is experimental evidence for such steps lacking for most pathways, despite intensive search, but there are also theoretical arguments against the idea that highly regulated enzymes catalyzing reactions far from equilibrium must be considered a priori rate limiting. Conversely, it is argued that reactions close to equilibrium need a lot of enzyme to be maintained close to equilibrium and, contrary to accepted wisdom, begin to limit flux when reduced. Using a few key examples of plant metabolic pathways as case studies, I draw some general conclusions. The approach of augmenting flux by pushing a pathway from above is well exemplified by the attempts at increasing starch content in potato tubers, where several different approaches failed. Also pulling at the other end (close to the end product) has yielded little improvement, while targeting a reaction close to equilibrium (ADP/ATP translocation at the plastid envelope) successfully increased starch content. Rethinking control is equally well applicable to photosynthesis, with prime examples of 'neglected', unregulated enzymes exerting significant control and overprized 'limiting' enzymes having little control in normal conditions like rubisco. In this new paradigm, the role of most control mechanisms is also challenged: feedback inhibition and post-translational modification of enzymes are relevant to metabolite homeostasis rather than flux control, with moiety conservation being a major reason for this constraint. I advocate a more extensive use of control circuitry elements (e.g. sensors like riboswitches), metabolic shortcuts and transcription factors in metabolic engineering.
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Affiliation(s)
- Piero Morandini
- Department of Biology, University of Milan, CNR, Institute of Biophysics, via Celoria 26, 20133 Milan, Italy.
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