1
|
Jasinska W, Dindo M, Cordoba SMC, Serohijos AWR, Laurino P, Brotman Y, Bershtein S. Non-consecutive enzyme interactions within TCA cycle supramolecular assembly regulate carbon-nitrogen metabolism. Nat Commun 2024; 15:5285. [PMID: 38902266 PMCID: PMC11189929 DOI: 10.1038/s41467-024-49646-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 06/14/2024] [Indexed: 06/22/2024] Open
Abstract
Enzymes of the central metabolism tend to assemble into transient supramolecular complexes. However, the functional significance of the interactions, particularly between enzymes catalyzing non-consecutive reactions, remains unclear. Here, by co-localizing two non-consecutive enzymes of the TCA cycle from Bacillus subtilis, malate dehydrogenase (MDH) and isocitrate dehydrogenase (ICD), in phase separated droplets we show that MDH-ICD interaction leads to enzyme agglomeration with a concomitant enhancement of ICD catalytic rate and an apparent sequestration of its reaction product, 2-oxoglutarate. Theory demonstrates that MDH-mediated clustering of ICD molecules explains the observed phenomena. In vivo analyses reveal that MDH overexpression leads to accumulation of 2-oxoglutarate and reduction of fluxes flowing through both the catabolic and anabolic branches of the carbon-nitrogen intersection occupied by 2-oxoglutarate, resulting in impeded ammonium assimilation and reduced biomass production. Our findings suggest that the MDH-ICD interaction is an important coordinator of carbon-nitrogen metabolism.
Collapse
Affiliation(s)
- Weronika Jasinska
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Mirco Dindo
- Protein Engineering and Evolution Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
- Department of Medicine and Surgery, Section of Physiology and Biochemistry, University of Perugia, Perugia, Italy
| | - Sandra M C Cordoba
- Max-Planck-Institut fur Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
| | - Adrian W R Serohijos
- Departement de Biochimie, Universite de Montreal, Quebec, Canada
- Centre Robert-Cedergren en Bio-informatique et Genomique, Universite de Montreal, Quebec, Canada
| | - Paola Laurino
- Protein Engineering and Evolution Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan.
- Institute for Protein Research, Osaka University, Suita, Japan.
| | - Yariv Brotman
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
| | - Shimon Bershtein
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
| |
Collapse
|
2
|
Linnenbrügger L, Doering L, Lansing H, Fischer K, Eirich J, Finkemeier I, von Schaewen A. Alternative splicing of Arabidopsis G6PD5 recruits NADPH-producing OPPP reactions to the endoplasmic reticulum. FRONTIERS IN PLANT SCIENCE 2022; 13:909624. [PMID: 36119606 PMCID: PMC9478949 DOI: 10.3389/fpls.2022.909624] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
Glucose-6-phosphate dehydrogenase is the rate-limiting enzyme of the oxidative pentose-phosphate pathway (OPPP). The OPPP mainly provides NADPH and sugar-phosphate building blocks for anabolic pathways and is present in all eukaryotes. In plant cells, the irreversible part of the OPPP is found in several compartments. Among the isoforms catalyzing the first OPPP step in Arabidopsis, G6PD1 to G6PD4 target plastids (with G6PD1 being also directed to peroxisomes), whereas G6PD5 and G6PD6 operate in the cytosol. We noticed that alternative splice forms G6PD5.4 and G6PD5.5 encode N-terminally extended proteoforms. Compared to G6PD5.1, RT-PCR signals differed and fluorescent reporter fusions expressed in Arabidopsis protoplasts accumulated in distinct intracellular sites. Co-expression with organelle-specific markers revealed that the G6PD5.4 and G6PD5.5 proteoforms label different subdomains of the endoplasmic reticulum (ER), and analysis of C-terminal roGFP fusions showed that their catalytic domains face the cytosol. In g6pd5-1 g6pd6-2 mutant protoplasts lacking cytosolic G6PDH activity, the ER-bound proteoforms were both active and thus able to form homomers. Among the Arabidopsis 6-phosphogluconolactonases (catalyzing the second OPPP step), we noticed that isoform PGL2 carries a C-terminal CaaX motif that may be prenylated for membrane attachment. Reporter-PGL2 fusions co-localized with G6PD5.4 in ER subdomains, which was abolished by Cys-to-Ser exchange in the 256CSIL motif. Among the Arabidopsis 6-phosphogluconate dehydrogenases (catalyzing the third OPPP step), S-acylated peptides were detected for all three isoforms in a recent palmitoylome, with dual cytosolic/peroxisomal PGD2 displaying three sites. Co-expression of GFP-PGD2 diminished crowding of OFP-G6PD5.4 at the ER, independent of PGL2's presence. Upon pull-down of GFP-G6PD5.4, not only unlabeled PGD2 and PGL2 were enriched, but also enzymes that depend on NADPH provision at the ER, indicative of physical interaction with the OPPP enzymes. When membrane-bound G6PD5.5 and 5.4 variants were co-expressed with KCR1 (ketoacyl-CoA reductase, involved in fatty acid elongation), ATR1 (NADPH:cytochrome-P450 oxidoreductase), or pulled C4H/CYP73A5 (cinnamate 4-hydroxylase) as indirectly (via ATR) NADPH-dependent cytochrome P450 enzyme, co-localization in ER subdomains was observed. Thus, alternative splicing of G6PD5 can direct the NADPH-producing OPPP reactions to the cytosolic face of the ER, where they may operate as membrane-bound metabolon to support several important biosynthetic pathways of plant cells.
Collapse
Affiliation(s)
- Loreen Linnenbrügger
- Department of Biology, Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Lennart Doering
- Department of Biology, Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Hannes Lansing
- Department of Biology, Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Kerstin Fischer
- Department of Biology, Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Jürgen Eirich
- Department of Biology, Plant Physiology, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Iris Finkemeier
- Department of Biology, Plant Physiology, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| | - Antje von Schaewen
- Department of Biology, Molecular Physiology of Plants, Institute of Plant Biology and Biotechnology, University of Münster (WWU Münster), Münster, Germany
| |
Collapse
|
3
|
Kondrat S, von Lieres E. Mechanisms and Effects of Substrate Channelling in Enzymatic Cascades. Methods Mol Biol 2022; 2487:27-50. [PMID: 35687228 DOI: 10.1007/978-1-0716-2269-8_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Substrate or metabolite channelling is a transfer of intermediates produced by one enzyme to the sequential enzyme of a reaction cascade or metabolic pathway, without releasing them entirely into bulk. Despite an enormous effort and more than three decades of research, substrate channelling remains the subject of continuing debates and active investigation. Herein, we review the benefits and mechanisms of substrate channelling in vivo and in vitro. We discuss critically the effects that substrate channelling can have on enzymatic cascades, including speeding up or slowing down reaction cascades and protecting intermediates from sequestration and enzymes' surroundings from toxic or otherwise detrimental intermediates. We also discuss how macromolecular crowding affects substrate channelling and point out the galore of open questions.
Collapse
Affiliation(s)
- Svyatoslav Kondrat
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.
- Max-Planck-Institut für Intelligente Systeme, Stuttgart, Germany.
- IV. Institut für Theoretische Physik, Universität Stuttgart, Stuttgart, Germany.
| | - Eric von Lieres
- Forschungszentrum Jülich, IBG-1: Biotechnology, Jülich, Germany
| |
Collapse
|
4
|
Lansing H, Doering L, Fischer K, Baune MC, Schaewen AV. Analysis of potential redundancy among Arabidopsis 6-phosphogluconolactonase isoforms in peroxisomes. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:823-836. [PMID: 31641750 DOI: 10.1093/jxb/erz473] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 10/10/2019] [Indexed: 05/21/2023]
Abstract
Recent work revealed that PGD2, an Arabidopsis 6-phosphogluconate dehydrogenase (6-PGD) catalysing the third step of the oxidative pentose-phosphate pathway (OPPP) in peroxisomes, is essential during fertilization. Earlier studies on the second step, catalysed by PGL3, a dually targeted Arabidopsis 6-phosphogluconolactonase (6-PGL), reported the importance of OPPP reactions in plastids but their irrelevance in peroxisomes. Assuming redundancy of 6-PGL activity in peroxisomes, we examined the sequences of other higher plant enzymes. In tomato, there exist two 6-PGL isoforms with the strong PTS1 motif SKL. However, their analysis revealed problems regarding peroxisomal targeting: reporter-PGL detection in peroxisomes required construct modification, which was also applied to the Arabidopsis isoforms. The relative contribution of PGL3 versus PGL5 during fertilization was assessed by mutant crosses. Reduced transmission ratios were found for pgl3-1 (T-DNA-eliminated PTS1) and also for knock-out allele pgl5-2. The prominent role of PGL3 showed as compromised growth of pgl3-1 seedlings on sucrose and higher activity of mutant PGL3-1 versus PGL5 using purified recombinant proteins. Evidence for PTS1-independent uptake was found for PGL3-1 and other Arabidopsis PGL isoforms, indicating that peroxisome import may be supported by a piggybacking mechanism. Thus, multiple redundancy at the level of the second OPPP step in peroxisomes explains the occurrence of pgl3-1 mutant plants.
Collapse
Affiliation(s)
- Hannes Lansing
- Molekulare Physiologie der Pflanzen, Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| | - Lennart Doering
- Molekulare Physiologie der Pflanzen, Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| | - Kerstin Fischer
- Molekulare Physiologie der Pflanzen, Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| | - Marie-Christin Baune
- Molekulare Physiologie der Pflanzen, Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| | - Antje Von Schaewen
- Molekulare Physiologie der Pflanzen, Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Schlossplatz 7, D-48149 Münster, Germany
| |
Collapse
|
5
|
Sweetlove LJ, Fernie AR. The role of dynamic enzyme assemblies and substrate channelling in metabolic regulation. Nat Commun 2018; 9:2136. [PMID: 29849027 PMCID: PMC5976638 DOI: 10.1038/s41467-018-04543-8] [Citation(s) in RCA: 238] [Impact Index Per Article: 39.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 05/08/2018] [Indexed: 11/08/2022] Open
Abstract
Transient physical association between enzymes appears to be a cardinal feature of metabolic systems, yet the purpose of this metabolic organisation remains enigmatic. It is generally assumed that substrate channelling occurs in these complexes. However, there is a lack of information concerning the mechanisms and extent of substrate channelling and confusion regarding the consequences of substrate channelling. In this review, we outline recent advances in the structural characterisation of enzyme assemblies and integrate this with new insights from reaction-diffusion modelling and synthetic biology to clarify the mechanistic and functional significance of the phenomenon.
Collapse
Affiliation(s)
- Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
| | - Alisdair R Fernie
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, 14476, Germany.
| |
Collapse
|
6
|
Lane S, Xu H, Oh EJ, Kim H, Lesmana A, Jeong D, Zhang G, Tsai CS, Jin YS, Kim SR. Glucose repression can be alleviated by reducing glucose phosphorylation rate in Saccharomyces cerevisiae. Sci Rep 2018; 8:2613. [PMID: 29422502 PMCID: PMC5805702 DOI: 10.1038/s41598-018-20804-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Accepted: 01/19/2018] [Indexed: 01/06/2023] Open
Abstract
Microorganisms commonly exhibit preferential glucose consumption and diauxic growth when cultured in mixtures of glucose and other sugars. Although various genetic perturbations have alleviated the effects of glucose repression on consumption of specific sugars, a broadly applicable mechanism remains unknown. Here, we report that a reduction in the rate of glucose phosphorylation alleviates the effects of glucose repression in Saccharomyces cerevisiae. Through adaptive evolution under a mixture of xylose and the glucose analog 2-deoxyglucose, we isolated a mutant strain capable of simultaneously consuming glucose and xylose. Genome sequencing of the evolved mutant followed by CRISPR/Cas9-based reverse engineering revealed that mutations in the glucose phosphorylating enzymes (Hxk1, Hxk2, Glk1) were sufficient to confer simultaneous glucose and xylose utilization. We then found that varying hexokinase expression with an inducible promoter led to the simultaneous utilization of glucose and xylose. Interestingly, no mutations in sugar transporters occurred during the evolution, and no specific transporter played an indispensable role in simultaneous sugar utilization. Additionally, we demonstrated that slowing glucose consumption also enabled simultaneous utilization of glucose and galactose. These results suggest that the rate of intracellular glucose phosphorylation is a decisive factor for metabolic regulations of mixed sugars.
Collapse
Affiliation(s)
- Stephan Lane
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Haiqing Xu
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Eun Joong Oh
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Heejin Kim
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Anastashia Lesmana
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Deokyeol Jeong
- School of Food Science and Biotechnology, Kyungpook National University, Daegu, Republic of Korea
| | - Guochang Zhang
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Ching-Sung Tsai
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Yong-Su Jin
- Carl Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA. .,Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
| | - Soo Rin Kim
- School of Food Science and Biotechnology, Kyungpook National University, Daegu, Republic of Korea. .,Institute of Agricultural Science & Technology, Kyungpook National University, Daegu, Republic of Korea.
| |
Collapse
|
7
|
Yao R, Pan K, Peng H, Feng L, Hu H, Zhang X. Engineering and systems-level analysis of Pseudomonas chlororaphis for production of phenazine-1-carboxamide using glycerol as the cost-effective carbon source. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:130. [PMID: 29755589 PMCID: PMC5934903 DOI: 10.1186/s13068-018-1123-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 04/19/2018] [Indexed: 05/21/2023]
Abstract
BACKGROUND Glycerol, an inevitable byproduct of biodiesel, has become an attractive feedstock for the production of value-added chemicals due to its availability and low price. Pseudomonas chlororaphis HT66 can use glycerol to synthesize phenazine-1-carboxamide (PCN), a phenazine derivative, which is strongly antagonistic to fungal phytopathogens. A systematic understanding of underlying mechanisms for the PCN overproduction will be important for the further improvement and industrialization. RESULTS We constructed a PCN-overproducing strain (HT66LSP) through knocking out three negative regulatory genes, lon, parS, and prsA in HT66. The strain HT66LSP produced 4.10 g/L of PCN with a yield of 0.23 (g/g) from glycerol, which was of the highest titer and the yield obtained among PCN-producing strains. We studied gene expression, metabolomics, and dynamic 13C tracer in HT66 and HT66LSP. In response to the phenotype changes, the transcript levels of phz biosynthetic genes, which are responsible for PCN biosynthesis, were all upregulated in HT66LSP. Central carbon was rerouted to the shikimate pathway, which was shown by the modulation of specific genes involved in the lower glycolysis, the TCA cycle, and the shikimate pathway, as well as changes in abundances of intracellular metabolites and flux distribution to increase the precursor availability for PCN biosynthesis. Moreover, dynamic 13C-labeling experiments revealed that the presence of metabolite channeling of 3-phosphoglyceric acid to phosphoenolpyruvate and shikimate to trans-2,3-dihydro-3-hydroxyanthranilic acid in HT66LSP could enable high-yielding synthesis of PCN. CONCLUSIONS The integrated analysis of gene expression, metabolomics, and dynamic 13C tracer enabled us to gain a more in-depth insight into complex mechanisms for the PCN overproduction. This study provides important basis for further engineering P. chlororaphis for high PCN production and efficient glycerol conversion.
Collapse
Affiliation(s)
- Ruilian Yao
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China
| | - Keli Pan
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China
| | - Huasong Peng
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China
| | - Lei Feng
- Instrumental Analysis Center, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China
| | - Hongbo Hu
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China
| | - Xuehong Zhang
- State Key Laboratory of Microbial Metabolism, and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China
| |
Collapse
|
8
|
Abernathy MH, He L, Tang YJ. Channeling in native microbial pathways: Implications and challenges for metabolic engineering. Biotechnol Adv 2017. [DOI: 10.1016/j.biotechadv.2017.06.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
9
|
He L, Xiu Y, Jones JA, Baidoo EE, Keasling JD, Tang YJ, Koffas MA. Deciphering flux adjustments of engineered E. coli cells during fermentation with changing growth conditions. Metab Eng 2017; 39:247-256. [DOI: 10.1016/j.ymben.2016.12.008] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 12/12/2016] [Accepted: 12/20/2016] [Indexed: 11/30/2022]
|
10
|
Hollinshead WD, Rodriguez S, Martin HG, Wang G, Baidoo EEK, Sale KL, Keasling JD, Mukhopadhyay A, Tang YJ. Examining Escherichia coli glycolytic pathways, catabolite repression, and metabolite channeling using Δ pfk mutants. BIOTECHNOLOGY FOR BIOFUELS 2016; 9:212. [PMID: 27766116 PMCID: PMC5057261 DOI: 10.1186/s13068-016-0630-y] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 09/28/2016] [Indexed: 05/09/2023]
Abstract
BACKGROUND Glycolysis breakdowns glucose into essential building blocks and ATP/NAD(P)H for the cell, occupying a central role in its growth and bio-production. Among glycolytic pathways, the Entner Doudoroff pathway (EDP) is a more thermodynamically favorable pathway with fewer enzymatic steps than either the Embden-Meyerhof-Parnas pathway (EMPP) or the oxidative pentose phosphate pathway (OPPP). However, Escherichia coli do not use their native EDP for glucose metabolism. RESULTS Overexpression of edd and eda in E. coli to enhance EDP activity resulted in only a small shift in the flux directed through the EDP (~20 % of glycolysis flux). Disrupting the EMPP by phosphofructokinase I (pfkA) knockout increased flux through OPPP (~60 % of glycolysis flux) and the native EDP (~14 % of glycolysis flux), while overexpressing edd and eda in this ΔpfkA mutant directed ~70 % of glycolytic flux through the EDP. The downregulation of EMPP via the pfkA deletion significantly decreased the growth rate, while EDP overexpression in the ΔpfkA mutant failed to improve its growth rates due to metabolic burden. However, the reorganization of E. coli glycolytic strategies did reduce glucose catabolite repression. The ΔpfkA mutant in glucose medium was able to cometabolize acetate via the citric acid cycle and gluconeogenesis, while EDP overexpression in the ΔpfkA mutant repressed acetate flux toward gluconeogenesis. Moreover, 13C-pulse experiments in the ΔpfkA mutants showed unsequential labeling dynamics in glycolysis intermediates, possibly suggesting metabolite channeling (metabolites in glycolysis are pass from enzyme to enzyme without fully equilibrating within the cytosol medium). CONCLUSIONS We engineered E. coli to redistribute its native glycolytic flux. The replacement of EMPP by EDP did not improve E. coli glucose utilization or biomass growth, but alleviated catabolite repression. More importantly, our results supported the hypothesis of channeling in the glycolytic pathways, a potentially overlooked mechanism for regulating glucose catabolism and coutilization of other substrates. The presence of channeling in native pathways, if proven true, would affect synthetic biology applications and metabolic modeling.
Collapse
Affiliation(s)
- Whitney D. Hollinshead
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO USA
| | - Sarah Rodriguez
- Sandia National Laboratory, Livermore, CA USA
- Joint BioEnergy Institute, Emeryville, CA USA
| | - Hector Garcia Martin
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - George Wang
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Edward E. K. Baidoo
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Kenneth L. Sale
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Jay D. Keasling
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
- California Institute of Quantitative Biosciences (QB3), University of California, Berkeley, CA USA
- Department of Bioengineering, University of California, Berkeley, CA USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA USA
- Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Allé, DK2970 Hørsholm, Denmark
| | - Aindrila Mukhopadhyay
- Joint BioEnergy Institute, Emeryville, CA USA
- Lawrence Berkeley National Laboratory, Biological Systems and Engineering Division, Berkeley, CA USA
| | - Yinjie J. Tang
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO USA
| |
Collapse
|
11
|
Moehlenbrock MJ, Meredith MT, Minteer SD. Bioelectrocatalytic Oxidation of Glucose in CNT Impregnated Hydrogels: Advantages of Synthetic Enzymatic Metabolon Formation. ACS Catal 2011. [DOI: 10.1021/cs200482v] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Michael J. Moehlenbrock
- Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, St. Louis, Missouri 63103, United States
| | - Matthew T. Meredith
- Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, St. Louis, Missouri 63103, United States
- Departments of Chemistry and Materials Science and Engineering, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, United States
| | - Shelley D. Minteer
- Department of Chemistry, Saint Louis University, 3501 Laclede Avenue, St. Louis, Missouri 63103, United States
- Departments of Chemistry and Materials Science and Engineering, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, United States
| |
Collapse
|
12
|
|
13
|
Zhang YHP. Substrate channeling and enzyme complexes for biotechnological applications. Biotechnol Adv 2011; 29:715-25. [PMID: 21672618 DOI: 10.1016/j.biotechadv.2011.05.020] [Citation(s) in RCA: 203] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Revised: 05/19/2011] [Accepted: 05/30/2011] [Indexed: 12/25/2022]
Abstract
Substrate channeling is a process of transferring the product of one enzyme to an adjacent cascade enzyme or cell without complete mixing with the bulk phase. Such phenomena can occur in vivo, in vitro, or ex vivo. Enzyme-enzyme or enzyme-cell complexes may be static or transient. In addition to enhanced reaction rates through substrate channeling in complexes, numerous potential benefits of such complexes are protection of unstable substrates, circumvention of unfavorable equilibrium and kinetics imposed, forestallment of substrate competition among different pathways, regulation of metabolic fluxes, mitigation of toxic metabolite inhibition, and so on. Here we review numerous examples of natural and synthetic complexes featuring substrate channeling. Constructing synthetic in vivo, in vitro or ex vivo complexes for substrate channeling would have great biotechnological potentials in metabolic engineering, multi-enzyme-mediated biocatalysis, and cell-free synthetic pathway biotransformation (SyPaB).
Collapse
Affiliation(s)
- Y-H Percival Zhang
- Biological Systems Engineering Department, 210-A Seitz Hall, Virginia Tech, Blacksburg, VA 24061, USA.
| |
Collapse
|
14
|
Moehlenbrock MJ, Toby TK, Pelster LN, Minteer SD. Metabolon Catalysts: An Efficient Model for Multi-enzyme Cascades at Electrode Surfaces. ChemCatChem 2011. [DOI: 10.1002/cctc.201000384] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
15
|
Characterization of Arabidopsis 6-Phosphogluconolactonase T-DNA Insertion Mutants Reveals an Essential Role for the Oxidative Section of the Plastidic Pentose Phosphate Pathway in Plant Growth and Development. ACTA ACUST UNITED AC 2009; 50:1277-91. [DOI: 10.1093/pcp/pcp070] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
16
|
Abstract
Fluxome analysis aims at the quantitative analysis of in vivo carbon fluxes in metabolic networks, i. e. intracellular activities of enzymes and pathways. It allows investigating the effects of genetic or environmental modifications and thus precisely provides a global perspective on the integrated genetic and metabolic regulation within the intact metabolic network. The experimental and computational approaches developed in this area have revealed fascinating insights into metabolic properties of various biological systems. Most of the comprehensive approaches for metabolic flux studies today involve isotopic tracer studies and GC-MS for measurement of the labeling pattern of metabolites. Initially developed and applied mainly in the field of biomedicine these GC-MS based metabolic flux approaches have been substantially extended and optimized during recent years and today display a key technology in metabolic physiology and biotechnology.
Collapse
Affiliation(s)
- Christoph Wittmann
- Biochemical Engineering Institute, Saarland University, Saarbrücken, Germany.
| |
Collapse
|
17
|
Walters JJ, Grayson MA, Gross ML, Hughes M, Shearer G, Kohl DH, Bashkin J. Ion-exchange chromatography followed by ESI-MS for quantitative analysis of sugar monophosphates from glucose catabolism. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2006; 17:104-107. [PMID: 16352445 DOI: 10.1016/j.jasms.2005.10.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2005] [Revised: 10/04/2005] [Accepted: 10/13/2005] [Indexed: 05/05/2023]
Abstract
The aim of this work is to establish a quantitative method to determine the ratio of [U-(13)C] labeled to unlabeled hexose monophosphates isolated from yeast extracts. This is accomplished by anion exchange chromatography and mobile phase desalting followed by electrospray (ESI) mass spectrometry. We test the method with the analysis of a sample of biological origin. Previously developed analytical techniques are not adequate to accomplish mass spectrometric analysis of these and other small monosaccharide systems because of interference from salt clusters. By lowering the ionic strength of the mobile phase and using a simplified injection system to the mass spectrometer, we were able to obtain data on the relative abundance of the hexose monophosphates.
Collapse
Affiliation(s)
- James J Walters
- Department of Chemistry, Washington University, One Brookings Drive, Campus Box 1134, 63130, St. Louis, MO, USA
- the Department of Chemistry and Biochemistry, University of Missouri, 63121, St. Louis, MO
| | - Michael A Grayson
- Department of Chemistry, Washington University, One Brookings Drive, Campus Box 1134, 63130, St. Louis, MO, USA
| | - Michael L Gross
- Department of Chemistry, Washington University, One Brookings Drive, Campus Box 1134, 63130, St. Louis, MO, USA.
| | - Maureen Hughes
- Department of Biology, Washington University, St. Louis, Missouri, USA
| | - Georgia Shearer
- Department of Biology, Washington University, St. Louis, Missouri, USA
| | - Daniel H Kohl
- Department of Biology, Washington University, St. Louis, Missouri, USA
| | - James Bashkin
- Department of Chemistry and Biochemistry, University of Missouri, St. Louis, Missouri, USA
| |
Collapse
|
18
|
Huang JB, Espinoza J, Romero R, Petty HR. Transaldolase is part of a supramolecular complex containing glucose-6-phosphate dehydrogenase in human neutrophils that undergoes retrograde trafficking during pregnancy. Metabolism 2005; 54:1027-33. [PMID: 16092052 DOI: 10.1016/j.metabol.2005.03.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Previous studies have shown that glucose-6-phosphate dehydrogenase (G6PDase) and 6-phosphogluconate dehydrogenase form a supramolecular complex in human neutrophils that undergoes retrograde trafficking in cells from pregnant women, but anterograde trafficking in cells from nonpregnant individuals. Using fluorescence resonance energy transfer techniques, we now demonstrate that transaldolase (TALase), a key regulatory enzyme in the nonoxidative branch of the hexose monophosphate shunt, is in close physical proximity with G6PDase, but not with lactate dehydrogenase, thus suggesting the formation of a TALase-G6PDase complex. Moreover, immunofluorescence microscopy demonstrated that TALase undergoes anterograde trafficking in neutrophils from nonpregnant individuals, whereas retrograde trafficking is found during pregnancy. However, pregnancy did not affect lactate dehydrogenase distribution. Colchicine treatment blocked the retrograde distribution of TALase, suggesting that microtubules are involved in TALase trafficking. We suggest that TALase is part of a supramolecular hexose monophosphate shunt complex, which likely increases the efficiency of the shunt via substrate channeling. We further suggest that TALase's retrograde motion contributes to uncoupling the shunt from its source of glucose-6-phosphate at the plasma membrane, thereby blunting nicotinamide adenine dinucleotide phosphate (reduced form) production and downstream oxidant production by neutrophils.
Collapse
Affiliation(s)
- Ji-Biao Huang
- Department of Ophthalmology and Visual Sciences, The University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | | | | | | |
Collapse
|
19
|
Shearer G, Lee JC, Koo JA, Kohl DH. Quantitative estimation of channeling from early glycolytic intermediates to CO2 in intact Escherichia coli. FEBS J 2005; 272:3260-9. [PMID: 15978033 DOI: 10.1111/j.1742-4658.2005.04712.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A pathway intermediate is said to be 'channeled' when an intermediate just made in a pathway has a higher probability of being a substrate for the next pathway enzyme compared with a molecule of the same species from the aqueous cytoplasm. Channeling is an important phenomenon because it might play a significant role in the regulation of metabolism. Whereas the usual mechanism proposed for channeling is the (often) transient interaction of sequential pathway enzymes, many of the supporting data come from results with pure enzymes and dilute cell extracts. Even when isotope dilution techniques have utilized whole-cell systems, most often only a qualitative assessment of channeling has been reported. Here we develop a method for making a quantitative calculation of the fraction channeled in glycolysis from in vivo isotope dilution experiments. We show that fructose-1,6-bisphosphate, in whole cells of Escherichia coli, was strongly channeled all the way to CO2, whereas fructose-6-phosphate was not. Because the signature of channeling is lost if any downstream intermediate prior to CO2 equilibrates with molecules in the aqueous cytosol, it was not possible to evaluate whether glucose-6-phosphate was channeled in its transformation to fructose-6-phosphate. The data also suggest that, in addition to pathway enzymes being associated with one another, some are free in the aqueous cytosol. How sensitive the degree of channeling is to growth or experimental conditions remains to be determined.
Collapse
Affiliation(s)
- Georgia Shearer
- Department of Biology, Washington University, St. Louis, MO 63130, USA
| | | | | | | |
Collapse
|
20
|
Kindzelskii AL, Ueki T, Michibata H, Chaiworapongsa T, Romero R, Petty HR. 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase form a supramolecular complex in human neutrophils that undergoes retrograde trafficking during pregnancy. THE JOURNAL OF IMMUNOLOGY 2004; 172:6373-81. [PMID: 15128828 DOI: 10.4049/jimmunol.172.10.6373] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Neutrophils from pregnant women display reduced neutrophil-mediated effector functions, such as reactive oxygen metabolite (ROM) release. Because the NADPH oxidase and NO synthase produce ROMs and NO, the availability of their substrate NADPH is a potential regulatory factor. NADPH is produced by glucose-6-phosphate dehydrogenase (G-6-PDase) and 6-phosphogluconate dehydrogenase (6-PGDase), which are the first two steps of the hexose monophosphate shunt (HMS). Using immunofluorescence microscopy, we show that 6-PGDase, like G-6-PDase, undergoes retrograde transport to the microtubule-organizing centers in neutrophils from pregnant women. In contrast, 6-PGDase is found in an anterograde distribution in cells from nonpregnant women. However, lactate dehydrogenase distribution is unaffected by pregnancy. Cytochemical studies demonstrated that the distribution of 6-PGDase enzymatic activity is coincident with 6-PGDase Ag. The accumulation of 6-PGDase at the microtubule-organizing centers could be blocked by colchicine, suggesting that microtubules are important in this enzyme's intracellular distribution. In situ kinetic studies reveal that the rates of 6-gluconate turnover are indistinguishable in samples from nonpregnant and pregnant women, suggesting that the enzyme is functionally intact. Resonance energy transfer experiments showed that 6-PGDase and G-6-PDase are in close physical proximity within cells, suggesting the presence of supramolecular enzyme complexes. We suggest that the retrograde trafficking of HMS enzyme complexes during pregnancy influences the dynamics of NADPH production by separating HMS enzymes from glucose-6-phosphate generation at the plasma membrane and, in parallel, reducing ROM and NO production in comparison with fully activated neutrophils from nonpregnant women.
Collapse
Affiliation(s)
- Andrei L Kindzelskii
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, MI 48105, USA
| | | | | | | | | | | |
Collapse
|
21
|
Yang J, Gu H, Yang Z. Likelihood analysis of the chalcone synthase genes suggests the role of positive selection in morning glories (Ipomoea). J Mol Evol 2004; 58:54-63. [PMID: 14743314 DOI: 10.1007/s00239-003-2525-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2003] [Accepted: 07/21/2003] [Indexed: 11/30/2022]
Abstract
Chalcone synthase (CHS) is a key enzyme in the biosynthesis of flavonoides, which are important for the pigmentation of flowers and act as attractants to pollinators. Genes encoding CHS constitute a multigene family in which the copy number varies among plant species and functional divergence appears to have occurred repeatedly. In morning glories (Ipomoea), five functional CHS genes (A-E) have been described. Phylogenetic analysis of the Ipomoea CHS gene family revealed that CHS A, B, and C experienced accelerated rates of amino acid substitution relative to CHS D and E. To examine whether the CHS genes of the morning glories underwent adaptive evolution, maximum-likelihood models of codon substitution were used to analyze the functional sequences in the Ipomoea CHS gene family. These models used the nonsynonymous/synonymous rate ratio (omega = d(N)/ d(S)) as an indicator of selective pressure and allowed the ratio to vary among lineages or sites. Likelihood ratio test suggested significant variation in selection pressure among amino acid sites, with a small proportion of them detected to be under positive selection along the branches ancestral to CHS A, B, and C. Positive Darwinian selection appears to have promoted the divergence of subfamily ABC and subfamily DE and is at least partially responsible for a rate increase following gene duplication.
Collapse
Affiliation(s)
- Ji Yang
- College of Life Sciences, Peking, University, Beijing, 100871, China
| | | | | |
Collapse
|
22
|
Moritz B, Striegel K, de Graaf AA, Sahm H. Changes of pentose phosphate pathway flux in vivo in Corynebacterium glutamicum during leucine-limited batch cultivation as determined from intracellular metabolite concentration measurements. Metab Eng 2002; 4:295-305. [PMID: 12646324 DOI: 10.1006/mben.2002.0233] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Corynebacterium glutamicum is an important organism for the industrial production of amino acids such as lysine. In the present study time-dependent changes in the oxidative pentose phosphate pathway activity, an important site of NADPH regeneration in C. glutamicum, are investigated, whereby intracellular metabolite concentrations and specific enzyme activities in two isogenic leucine auxotrophic strains differing only in the regulation of their aspartate kinases were compared. After leucine limitation only the strain with a feedback-resistant aspartate kinase began to excrete lysine into the culture medium. Concomitantly, the intracellular NADPH to NADP concentration ratio increased from 2 to 4 in the non-producing strain, whereas it remained constant at about 1.2 in the lysine-producing strain. From these data the in'vivo flux through the pentose phosphate pathway was calculated. These results were used to approximate the total NADPH regeneration by glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and isocitrate dehydrogenase, which agreed fairly well with the calculated demands for biomass formation and lysine biosynthesis. The analysis allowed to conclude that NADPH regeneration in the pentose phosphate pathway is essential for lysine biosynthesis in C. glutamicum.
Collapse
Affiliation(s)
- Bernd Moritz
- Institut für Biotechnologie I, Forschungszentrum Jülich GmbH, Germany
| | | | | | | |
Collapse
|
23
|
Wittmann C. Metabolic flux analysis using mass spectrometry. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2002; 74:39-64. [PMID: 11991183 DOI: 10.1007/3-540-45736-4_3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Detailed knowledge on carbon flux distributions is crucial for the understanding and targeted optimization of cellular systems. Analytical methods to identify the topology of metabolic networks and to quantify fluxes through its different pathways are therefore in the core of metabolic engineering. An elegant approach for metabolic flux analysis is provided by tracer experiments. In such studies tracer substrates with stable isotopes such as 13C are applied and the labeling pattern of metabolites is subsequently measured. Detailed flux distributions can be obtained by a combination of tracer experiments and stoichiometric balancing. In recent years, mass spectrometry (MS) has emerged as an interesting method for labeling measurements in metabolic flux analysis and provided valuable insights into the cellular metabolism. The present review provides an overview on current experimental and modeling tools for metabolic flux analysis by MS. The application of MS for flux analysis is illustrated by examples from the literature for various biological systems, including bacteria, fungi, tissue cultures and in vivo studies in humans.
Collapse
Affiliation(s)
- C Wittmann
- Biochemical Engineering Institute, Saarland University, Saarbruecken, Germany.
| |
Collapse
|
24
|
van Winden W, Verheijen P, Heijnen S. Possible pitfalls of flux calculations based on (13)C-labeling. Metab Eng 2001; 3:151-62. [PMID: 11289791 DOI: 10.1006/mben.2000.0174] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Metabolic engineers have enthusiastically adopted the (13)C-labeling technique as a powerful tool for elucidating fluxes in metabolic networks. This tracer technique makes it possible to determine fluxes that are unobservable using only metabolite balances and allows the elimination of doubtful cofactor balances that are indispensable in flux analysis based on metabolite balancing alone. The (13)C-labeling technique, however, relies on a number of assumptions that are not free from uncertainties. Two possible errors in the models that are needed to determine the metabolic fluxes from labeling data are omitted reactions and ignored occurrence of channeling. By means of two representative examples it is shown that these modeling errors may lead to serious errors in the calculated flux distributions despite the use of labeling data. A complicating fact is that the model errors are not always easily detected as poor models may still yield good fits of experimental data. Results of (13)C-labeling experiments should therefore be interpreted with appropriate caution.
Collapse
Affiliation(s)
- W van Winden
- Bioprocestechnology Group, Faculty of Applied Sciences, Delft University of Technology, The Netherlands.
| | | | | |
Collapse
|
25
|
Abstract
Plant peroxisomes can be isolated by Percoll density gradient centrifugation at high purity and metabolic competence as well as in relatively large quantities. According to biochemical and electrophysiological analyses, plant peroxisomes have recently been shown to differ from other cell organelles in essential structural properties. Unlike mitochondria or plastids, compartmentalization of plant peroxisomal metabolism is in major parts not caused by a boundary function of the membrane but is primarily due to the specific structure of the protein matrix. The enzymes of the photorespiratory C2 cycle of leaf peroxisomes are arranged as multienzyme complexes that allow efficient metabolic channelling with high flux rates and minimum leakage of reactive oxygen species from the organelle. Transfer of metabolites, such as carboxylates, proceeds across the peroxisomal membrane via a porin-like channel, which represents a relatively unspecific but highly efficient transport system. Because all variants of peroxisomes, which all contain only a single boundary membrane, are confronted with the task of transporting a large group of metabolites while preventing the escape of reactive intermediates, it is reasonable to speculate that the unique compartmentalization feature of leaf peroxisomes also applies to peroxisomes from fungi and mammals.
Collapse
Affiliation(s)
- S Reumann
- Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung für Biochemie der Pflanze, Göttingen, Germany.
| |
Collapse
|
26
|
Moritz B, Striegel K, De Graaf AA, Sahm H. Kinetic properties of the glucose-6-phosphate and 6-phosphogluconate dehydrogenases from Corynebacterium glutamicum and their application for predicting pentose phosphate pathway flux in vivo. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:3442-52. [PMID: 10848959 DOI: 10.1046/j.1432-1327.2000.01354.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The glucose-6-phosphate (Glc6P) and 6-phosphogluconate (6PG) dehydrogenases of the amino-acid-producing bacterium Corynebacterium glutamicum were purified to homogeneity and kinetically characterized. The Glc6P dehydrogenase was a heteromultimeric complex, which consists of Zwf and OpcA subunits. The product inhibition pattern of the Glc6P dehydrogenase was consistent with an ordered bi-bi mechanism. The 6PG dehydrogenase was found to operate according to a Theorell-Chance ordered bi-ter mechanism. Both enzymes were inhibited by NADPH and the 6PG dehydrogenase additionally by ATP, fructose 1,6-bisphosphate (Fru1,6P2), D-glyceraldehyde 3-phosphate (Gra3P), erythrose 4-phosphate and ribulose 5-phosphate (Rib5P). The inhibition by NADPH was considered to be most important, with inhibition constants of around 25 microM for both enzymes. Intracellular metabolite concentrations were determined in two isogenic strains of C. glutamicum with plasmid-encoded NAD- and NADP-dependent glutamate dehydrogenases. NADP+ and NADPH levels were between 130 microM and 290 microM, which is very much higher than the respective Km and Ki values. The Glc6P concentration was around 500 microM in both strains. The in vivo fluxes through the oxidative part of the pentose phosphate pathway calculated on the basis of intracellular metabolite concentrations and the kinetic constants of the purified enzymes determined in vitro were in agreement with the same fluxes determined by NMR after 13C-labelling. From the derived kinetic model thus validated, it is concluded that the oxidative pentose phosphate pathway in C. glutamicum is mainly regulated by the ratio of NADPH and NADP+ concentrations and the specific enzyme activities of both dehydrogenases.
Collapse
Affiliation(s)
- B Moritz
- Institut für Biotechnologie I, Jülich, Germany
| | | | | | | |
Collapse
|
27
|
|