1
|
Lao-Martil D, Verhagen KJA, Schmitz JPJ, Teusink B, Wahl SA, van Riel NAW. Kinetic Modeling of Saccharomyces cerevisiae Central Carbon Metabolism: Achievements, Limitations, and Opportunities. Metabolites 2022; 12:74. [PMID: 35050196 PMCID: PMC8779790 DOI: 10.3390/metabo12010074] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 01/11/2022] [Accepted: 01/12/2022] [Indexed: 11/23/2022] Open
Abstract
Central carbon metabolism comprises the metabolic pathways in the cell that process nutrients into energy, building blocks and byproducts. To unravel the regulation of this network upon glucose perturbation, several metabolic models have been developed for the microorganism Saccharomyces cerevisiae. These dynamic representations have focused on glycolysis and answered multiple research questions, but no commonly applicable model has been presented. This review systematically evaluates the literature to describe the current advances, limitations, and opportunities. Different kinetic models have unraveled key kinetic glycolytic mechanisms. Nevertheless, some uncertainties regarding model topology and parameter values still limit the application to specific cases. Progressive improvements in experimental measurement technologies as well as advances in computational tools create new opportunities to further extend the model scale. Notably, models need to be made more complex to consider the multiple layers of glycolytic regulation and external physiological variables regulating the bioprocess, opening new possibilities for extrapolation and validation. Finally, the onset of new data representative of individual cells will cause these models to evolve from depicting an average cell in an industrial fermenter, to characterizing the heterogeneity of the population, opening new and unseen possibilities for industrial fermentation improvement.
Collapse
Affiliation(s)
- David Lao-Martil
- Department of Biomedical Engineering, Eindhoven University of Technology, Groene Loper 5, 5612 AE Eindhoven, The Netherlands;
| | - Koen J. A. Verhagen
- Lehrstuhl für Bioverfahrenstechnik, FAU Erlangen-Nürnberg, 91052 Erlangen, Germany; (K.J.A.V.); (S.A.W.)
| | - Joep P. J. Schmitz
- DSM Biotechnology Center, Alexander Fleminglaan 1, 2613 AX Delft, The Netherlands;
| | - Bas Teusink
- Systems Biology Lab, Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit Amsterdam, 1081 HZ Amsterdam, The Netherlands;
| | - S. Aljoscha Wahl
- Lehrstuhl für Bioverfahrenstechnik, FAU Erlangen-Nürnberg, 91052 Erlangen, Germany; (K.J.A.V.); (S.A.W.)
| | - Natal A. W. van Riel
- Department of Biomedical Engineering, Eindhoven University of Technology, Groene Loper 5, 5612 AE Eindhoven, The Netherlands;
- Amsterdam University Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| |
Collapse
|
2
|
Hamill PG, Stevenson A, McMullan PE, Williams JP, Lewis ADR, S S, Stevenson KE, Farnsworth KD, Khroustalyova G, Takemoto JY, Quinn JP, Rapoport A, Hallsworth JE. Microbial lag phase can be indicative of, or independent from, cellular stress. Sci Rep 2020; 10:5948. [PMID: 32246056 PMCID: PMC7125082 DOI: 10.1038/s41598-020-62552-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 03/16/2020] [Indexed: 01/01/2023] Open
Abstract
Measures of microbial growth, used as indicators of cellular stress, are sometimes quantified at a single time-point. In reality, these measurements are compound representations of length of lag, exponential growth-rate, and other factors. Here, we investigate whether length of lag phase can act as a proxy for stress, using a number of model systems (Aspergillus penicillioides; Bacillus subtilis; Escherichia coli; Eurotium amstelodami, E. echinulatum, E. halophilicum, and E. repens; Mrakia frigida; Saccharomyces cerevisiae; Xerochrysium xerophilum; Xeromyces bisporus) exposed to mechanistically distinct types of cellular stress including low water activity, other solute-induced stresses, and dehydration-rehydration cycles. Lag phase was neither proportional to germination rate for X. bisporus (FRR3443) in glycerol-supplemented media (r2 = 0.012), nor to exponential growth-rates for other microbes. In some cases, growth-rates varied greatly with stressor concentration even when lag remained constant. By contrast, there were strong correlations for B. subtilis in media supplemented with polyethylene-glycol 6000 or 600 (r2 = 0.925 and 0.961), and for other microbial species. We also analysed data from independent studies of food-spoilage fungi under glycerol stress (Aspergillus aculeatinus and A. sclerotiicarbonarius); mesophilic/psychrotolerant bacteria under diverse, solute-induced stresses (Brochothrix thermosphacta, Enterococcus faecalis, Pseudomonas fluorescens, Salmonella typhimurium, Staphylococcus aureus); and fungal enzymes under acid-stress (Terfezia claveryi lipoxygenase and Agaricus bisporus tyrosinase). These datasets also exhibited diversity, with some strong- and moderate correlations between length of lag and exponential growth-rates; and sometimes none. In conclusion, lag phase is not a reliable measure of stress because length of lag and growth-rate inhibition are sometimes highly correlated, and sometimes not at all.
Collapse
Affiliation(s)
- Philip G Hamill
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - Andrew Stevenson
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - Phillip E McMullan
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - James P Williams
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - Abiann D R Lewis
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - Sudharsan S
- Department of Chemistry, PGP College of Arts and Science, NH-7, Karur Main Road, Paramathi, Namakkal, Tamil Nadu, 637 207, India
| | - Kath E Stevenson
- Special Collections and Archives, McClay Library, Queen's University Belfast, 10 College Park Avenue, Belfast, BT7 1LP, Northern Ireland
| | - Keith D Farnsworth
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - Galina Khroustalyova
- Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Str., 1-537, LV-1004, Riga, Latvia
| | - Jon Y Takemoto
- Utah State University, Department of Biology, 5305 Old Main Hill, Logan, UT, 84322, USA
| | - John P Quinn
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland
| | - Alexander Rapoport
- Laboratory of Cell Biology, Institute of Microbiology and Biotechnology, University of Latvia, Jelgavas Str., 1-537, LV-1004, Riga, Latvia
| | - John E Hallsworth
- Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast, BT9 5DL, Northern Ireland.
| |
Collapse
|
3
|
Takaine M, Ueno M, Kitamura K, Imamura H, Yoshida S. Reliable imaging of ATP in living budding and fission yeast. J Cell Sci 2019; 132:jcs.230649. [PMID: 30858198 DOI: 10.1242/jcs.230649] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 03/04/2019] [Indexed: 01/12/2023] Open
Abstract
Adenosine triphosphate (ATP) is a main metabolite essential for all living organisms. However, our understanding of ATP dynamics within a single living cell is very limited. Here, we optimized the ATP-biosensor QUEEN and monitored the dynamics of ATP with good spatial and temporal resolution in living yeasts. We found stable maintenance of ATP concentration in wild-type yeasts, regardless of carbon sources or cell cycle stages, suggesting that mechanism exists to maintain ATP at a specific concentration. We further found that ATP concentration is not necessarily an indicator of metabolic activity, as there is no clear correlation between ATP level and growth rates. During fission yeast meiosis, we found a reduction in ATP levels, suggesting that ATP homeostasis is controlled by differentiation. The use of QUEEN in yeasts offers an easy and reliable assay for ATP dynamicity and will answer several unaddressed questions about cellular metabolism in eukaryotes.
Collapse
Affiliation(s)
- Masak Takaine
- Gunma University Initiative for Advanced Research (GIAR), Gunma University, Maebashi 371-8512, Japan .,Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512, Japan
| | - Masaru Ueno
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Japan.,Research Center for the Mathematics on Chromatin Live Dynamics, Hiroshima University, Japan
| | - Kenji Kitamura
- Center for Gene Science, Hiroshima University, 1-4-2 Kagamiyama, Higashi-Hiroshima 739-8527, Japan
| | - Hiromi Imamura
- Department of Functional Biology, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Satoshi Yoshida
- Gunma University Initiative for Advanced Research (GIAR), Gunma University, Maebashi 371-8512, Japan .,Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512, Japan.,School of International Liberal Studies, Waseda University, Tokyo, 169-8050, Japan.,Japan Science and Technology Agency, PREST
| |
Collapse
|
4
|
Vrabl P, Schinagl CW, Artmann DJ, Krüger A, Ganzera M, Pötsch A, Burgstaller W. The Dynamics of Plasma Membrane, Metabolism and Respiration (PM-M-R) in Penicillium ochrochloron CBS 123824 in Response to Different Nutrient Limitations-A Multi-level Approach to Study Organic Acid Excretion in Filamentous Fungi. Front Microbiol 2017; 8:2475. [PMID: 29312185 PMCID: PMC5732977 DOI: 10.3389/fmicb.2017.02475] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 11/29/2017] [Indexed: 11/23/2022] Open
Abstract
Filamentous fungi are important cell factories. In contrast, we do not understand well even basic physiological behavior in these organisms. This includes the widespread phenomenon of organic acid excretion. One strong hurdle to fully exploit the metabolic capacity of these organisms is the enormous, highly environment sensitive phenotypic plasticity. In this work we explored organic acid excretion in Penicillium ochrochloron from a new point of view by simultaneously investigating three essential metabolic levels: the plasma membrane H+-ATPase (PM); energy metabolism, in particular adenine and pyridine nucleotides (M); and respiration, in particular the alternative oxidase (R). This was done in strictly standardized chemostat culture with different nutrient limitations (glucose, ammonium, nitrate, and phosphate). These different nutrient limitations led to various quantitative phenotypes (as represented by organic acid excretion, oxygen consumption, glucose consumption, and biomass formation). Glucose-limited grown mycelia were used as the reference point (very low organic acid excretion). Both ammonium and phosphate grown mycelia showed increased organic acid excretion, although the patterns of excreted acids were different. In ammonium-limited grown mycelia amount and activity of the plasma membrane H+-ATPase was increased, nucleotide concentrations were decreased, energy charge (EC) and catabolic reduction charge (CRC) were unchanged and alternative respiration was present but not quantifiable. In phosphate-limited grown mycelia (no data on the H+-ATPase) nucleotide concentrations were still lower, EC was slightly decreased, CRC was distinctly decreased and alternative respiration was present and quantifiable. Main conclusions are: (i) the phenotypic plasticity of filamentous fungi demands adaptation of sample preparation and analytical methods at the phenotype level; (ii) each nutrient condition is unique and its metabolic situation must be considered separately; (iii) organic acid excretion is inversely related to nucleotide concentration (but not EC); (iv) excretion of organic acids is the outcome of a simultaneous adjustment of several metabolic levels to nutrient conditions.
Collapse
Affiliation(s)
- Pamela Vrabl
- Institute of Microbiology, University of Innsbruck, Innsbruck, Austria
| | | | | | - Anja Krüger
- Institute of Pharmacy/Pharmacognosy, University of Innsbruck, Innsbruck, Austria
| | - Markus Ganzera
- Institute of Pharmacy/Pharmacognosy, University of Innsbruck, Innsbruck, Austria
| | - Ansgar Pötsch
- Plant Biochemistry, Ruhr University Bochum, Bochum, Germany
- School of Biomedical and Healthcare Sciences, Plymouth University, Plymouth, United Kingdom
| | | |
Collapse
|
5
|
Nikolaev YV, Kochanowski K, Link H, Sauer U, Allain FHT. Systematic Identification of Protein-Metabolite Interactions in Complex Metabolite Mixtures by Ligand-Detected Nuclear Magnetic Resonance Spectroscopy. Biochemistry 2016; 55:2590-600. [PMID: 27065204 DOI: 10.1021/acs.biochem.5b01291] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein-metabolite interactions play a vital role in the regulation of numerous cellular processes. Consequently, identifying such interactions is a key prerequisite for understanding cellular regulation. However, the noncovalent nature of the binding between proteins and metabolites has so far hampered the development of methods for systematically mapping protein-metabolite interactions. The few available, largely mass spectrometry-based, approaches are restricted to specific metabolite classes, such as lipids. In this study, we address this issue and show the potential of ligand-detected nuclear magnetic resonance (NMR) spectroscopy, which is routinely used in drug development, to systematically identify protein-metabolite interactions. As a proof of concept, we selected four well-characterized bacterial and mammalian proteins (AroG, Eno, PfkA, and bovine serum albumin) and identified metabolite binders in complex mixes of up to 33 metabolites. Ligand-detected NMR captured all of the reported protein-metabolite interactions, spanning a full range of physiologically relevant Kd values (low micromolar to low millimolar). We also detected a number of novel interactions, such as promiscuous binding of the negatively charged metabolites citrate, AMP, and ATP, as well as binding of aromatic amino acids to AroG protein. Using in vitro enzyme activity assays, we assessed the functional relevance of these novel interactions in the case of AroG and show that l-tryptophan, l-tyrosine, and l-histidine act as novel inhibitors of AroG activity. Thus, we conclude that ligand-detected NMR is suitable for the systematic identification of functionally relevant protein-metabolite interactions.
Collapse
Affiliation(s)
- Yaroslav V Nikolaev
- Institute of Molecular Biology & Biophysics, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Karl Kochanowski
- Institute of Molecular Systems Biology, ETH Zürich , CH-8093 Zürich, Switzerland.,Life Science Zurich PhD Program on Systems Biology , Zurich, Switzerland
| | - Hannes Link
- Institute of Molecular Systems Biology, ETH Zürich , CH-8093 Zürich, Switzerland.,Max-Planck Institute for Terrestrial Microbiology , Marburg, Germany
| | - Uwe Sauer
- Institute of Molecular Systems Biology, ETH Zürich , CH-8093 Zürich, Switzerland
| | - Frederic H-T Allain
- Institute of Molecular Biology & Biophysics, ETH Zürich , CH-8093 Zürich, Switzerland
| |
Collapse
|
6
|
Pseudo-transition Analysis Identifies the Key Regulators of Dynamic Metabolic Adaptations from Steady-State Data. Cell Syst 2015; 1:270-82. [DOI: 10.1016/j.cels.2015.09.008] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Revised: 08/12/2015] [Accepted: 09/30/2015] [Indexed: 11/20/2022]
|
7
|
Kochanowski K, Sauer U, Noor E. Posttranslational regulation of microbial metabolism. Curr Opin Microbiol 2015; 27:10-7. [PMID: 26048423 DOI: 10.1016/j.mib.2015.05.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 05/04/2015] [Accepted: 05/08/2015] [Indexed: 10/23/2022]
Abstract
Fluxes in microbial metabolism are controlled by various regulatory layers that alter abundance or activity of metabolic enzymes. Recent studies suggest a division of labor between these layers: transcriptional regulation mostly controls the allocation of protein resources, passive flux regulation by enzyme saturation and thermodynamics allows rapid responses at the expense of higher protein cost, and posttranslational regulation is utilized by cells to directly take control of metabolic decisions. We present recent advances in elucidating the role of these regulatory layers, focusing on posttranslational modifications and allosteric interactions. As the systematic mapping of posttranslational regulatory events has now become possible, the next challenge is to identify those regulatory events that are functionally relevant under a given condition.
Collapse
Affiliation(s)
- Karl Kochanowski
- Institute of Molecular Systems Biology, ETH Zurich, Auguste-Piccard-Hof 1, CH-8093 Zurich, Switzerland; Life Science Zurich PhD Program on Systems Biology, Zurich, Switzerland
| | - Uwe Sauer
- Institute of Molecular Systems Biology, ETH Zurich, Auguste-Piccard-Hof 1, CH-8093 Zurich, Switzerland.
| | - Elad Noor
- Institute of Molecular Systems Biology, ETH Zurich, Auguste-Piccard-Hof 1, CH-8093 Zurich, Switzerland
| |
Collapse
|
8
|
Guo Z, Olsson L. Physiological response of Saccharomyces cerevisiae to weak acids present in lignocellulosic hydrolysate. FEMS Yeast Res 2014; 14:1234-48. [PMID: 25331461 DOI: 10.1111/1567-1364.12221] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2014] [Revised: 10/05/2014] [Accepted: 10/08/2014] [Indexed: 01/15/2023] Open
Abstract
Weak acids are present in lignocellulosic hydrolysate as potential inhibitors that can hamper the use of this renewable resource for fuel and chemical production. To study the effects of weak acids on yeast growth, physiological investigations were carried out in batch cultures using glucose as carbon source in the presence of acetic, formic, levulinic, and vanillic acid at three different concentrations at pH 5.0. The results showed that acids at moderate concentrations can stimulate the glycolytic flux, while higher levels of acid slow down the glycolytic flux for both aerobically and anaerobically grown yeast cells. In particular, the flux distribution between respiratory and fermentative growth was adjusted to achieve an optimal ATP generation to allow a maintained energy level as high as it is in nonstressed cells grown exponentially on glucose under aerobic conditions. In addition, yeast cells exposed to acids suffered from severe reactive oxygen species stress and depletion of reduced glutathione commensurate with exhaustion of the total glutathione pool. Furthermore, a higher cellular trehalose content was observed as compared to control cultivations, and this trehalose probably acts to enhance a number of stress tolerances of the yeast.
Collapse
Affiliation(s)
- Zhongpeng Guo
- Department of Chemical and Biological Engineering, Industrial Biotechnology, Chalmers University of Technology, Gothenburg, Sweden
| | | |
Collapse
|
9
|
van Heerden JH, Bruggeman FJ, Teusink B. Multi-tasking of biosynthetic and energetic functions of glycolysis explained by supply and demand logic. Bioessays 2014; 37:34-45. [PMID: 25350875 DOI: 10.1002/bies.201400108] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
After more than a century of research on glycolysis, we have detailed descriptions of its molecular organization, but despite this wealth of knowledge, linking the enzyme properties to metabolic pathway behavior remains challenging. These challenges arise from multi-layered regulation and the context and time dependence of component functions. However, when viewed as a system that functions according to the principles of supply and demand, a simplifying theoretical framework can be applied to study its regulation logic and to assess the coherence of experimental interpretations. These principles are universally applicable, as they emphasize the common metabolic tasks of glycolysis: the provision of free-energy carriers, and precursors for biosynthesis and stress-related compounds. Here we will review the regulation of multi-tasking by glycolysis and consider how an understanding of this central metabolic pathway can be pursued using general principles, rather than focusing on the biochemical details of constituent components.
Collapse
Affiliation(s)
- Johan H van Heerden
- Systems Bioinformatics, AIMMS, NISB, VU University, Amsterdam, The Netherlands; Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands
| | | | | |
Collapse
|
10
|
Abstract
Beyond fuelling cellular activities with building blocks and energy, metabolism also integrates environmental conditions into intracellular signals. The underlying regulatory network is complex and multifaceted: it ranges from slow interactions, such as changing gene expression, to rapid ones, such as the modulation of protein activity via post-translational modification or the allosteric binding of small molecules. In this Review, we outline the coordination of common metabolic tasks, including nutrient uptake, central metabolism, the generation of energy, the supply of amino acids and protein synthesis. Increasingly, a set of key metabolites is recognized to control individual regulatory circuits, which carry out specific functions of information input and regulatory output. Such a modular view of microbial metabolism facilitates an intuitive understanding of the molecular mechanisms that underlie cellular decision making.
Collapse
|
11
|
Reddy GK, Wendisch VF. Characterization of 3-phosphoglycerate kinase from Corynebacterium glutamicum and its impact on amino acid production. BMC Microbiol 2014; 14:54. [PMID: 24593686 PMCID: PMC3996851 DOI: 10.1186/1471-2180-14-54] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Accepted: 02/26/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Corynebacterium glutamicum cg1790/pgk encodes an enzyme active as a 3-phosphoglycerate kinase (PGK) (EC 2.7.2.3) catalyzing phosphoryl transfer from 1,3-biphosphoglycerate (bPG) to ADP to yield 3-phosphoglycerate (3-PG) and ATP in substrate chain phosphorylation. RESULTS C. glutamicum 3-phosphoglycerate kinase was purified to homogeneity from the soluble fraction of recombinant E. coli. PGK(His) was found to be active as a homodimer with molecular weight of 104 kDa. The enzyme preferred conditions of pH 7.0 to 7.4 and required Mg²⁺ for its activity. PGK(His) is thermo labile and it has shown maximal activity at 50-65°C. The maximal activity of PGK(His) was estimated to be 220 and 150 U mg-1 with KM values of 0.26 and 0.11 mM for 3-phosphoglycerate and ATP, respectively. A 3-phosphoglycerate kinase negative C. glutamicum strain ∆pgk was constructed and shown to lack the ability to grow under glycolytic or gluconeogenic conditions unless PGK was expressed from a plasmid to restore growth. When pgk was overexpressed in L-arginine and L-ornithine production strains the production increased by 8% and by 17.5%, respectively. CONCLUSION Unlike many bacterial PGKs, C. glutamicum PGK is active as a homodimer. PGK is essential for growth of C. glutamicum with carbon sources requiring glycolysis and gluconeogenesis. Competitive inhibition by ADP reveals the critical role of PGK in gluconeogenesis by energy charge. Pgk overexpression improved the productivity in L-arginine and L-ornithine production strains.
Collapse
Affiliation(s)
| | - Volker F Wendisch
- Genetics of Prokaryotes, Faculty of Biology & CeBiTec, University of Bielefeld, Bielefeld 33615, Germany.
| |
Collapse
|
12
|
Link H, Christodoulou D, Sauer U. Advancing metabolic models with kinetic information. Curr Opin Biotechnol 2014; 29:8-14. [PMID: 24534671 DOI: 10.1016/j.copbio.2014.01.015] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 01/18/2014] [Accepted: 01/23/2014] [Indexed: 12/21/2022]
Abstract
Kinetic models are crucial to quantitatively understand and predict how functional behavior emerges from dynamic concentration changes of cellular components. The current challenge is on resolving uncertainties about parameter values of reaction kinetics. Additionally, there are also major structural uncertainties due to unknown molecular interactions and only putatively assigned regulatory functions. What if one or few key regulators of biochemical reactions are missing in a metabolic model? By reviewing current advances in building kinetic models of metabolism, we found that such models experience a paradigm shift away from fitting parameters towards identifying key regulatory interactions.
Collapse
Affiliation(s)
- Hannes Link
- Institute of Molecular Systems Biology, ETH Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland
| | - Dimitris Christodoulou
- Institute of Molecular Systems Biology, ETH Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland; Life Science Zurich PhD Program on Systems Biology, Zurich, Switzerland
| | - Uwe Sauer
- Institute of Molecular Systems Biology, ETH Zurich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland.
| |
Collapse
|