共查询到20条相似文献,搜索用时 31 毫秒
1.
The activities of enzymes of pentose phosphate pathway (PPP) viz. glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and carbon metabolism viz. phosphoenol pyruvate carboxylase, NADP- isocitrate dehydrogenase and NADP-malic enzyme were measured in the plant and bacteroid
fractions of mungbean (ureide exporter) and lentil (amide exporter) nodules along with the developing roots for comparison.
The enzymes of pentose phosphate pathway in legume cytosol had higher activities at a stage of maximum nitrogenase activity
and higher sucrose metabolism. However, bacteroids had only limited capacity for this pathway. The specific activities of
these enzymes were greater in ureide than in amide exporter. CO2 fixation via higher activity of phosphoenolpyruvate carboxylase in the plant part of the nodules in lentil might have been due to the
greater synthesis of four carbon amino acids for amide export. The peak of NADP-isocitrate dehydrogenase in both legumes coincided
with the pentose phosphate pathway enzymes at the time of high rates of sucrose metabolism and nitrogen fixation. Higher activities
of NADP-malic enzyme were obtained in mungbean than in the lentil nodules. These findings are consistent with the role of
these enzymes in providing reductant (NADPH) and substrates for energy yielding metabolism of bacteroids and carbon skeletons
for ammonia assimilation. 相似文献
2.
Eduardo Castro‐Torres Pedro Jimnez‐Sandoval Sergio Romero‐Romero Alma Fuentes‐Pascacio Laura M. Lpez‐Castillo Corina Díaz‐Quezada D. Alejandro Fernndez‐Velasco Alfredo Torres‐Larios Luis G. Brieba 《The Plant journal : for cell and molecular biology》2019,99(5):950-964
Reactive oxidative species (ROS) and S‐glutathionylation modulate the activity of plant cytosolic triosephosphate isomerases (cTPI). Arabidopsis thaliana cTPI (AtcTPI) is subject of redox regulation at two reactive cysteines that function as thiol switches. Here we investigate the role of these residues, AtcTPI‐Cys13 and At‐Cys218, by substituting them with aspartic acid that mimics the irreversible oxidation of cysteine to sulfinic acid and with amino acids that mimic thiol conjugation. Crystallographic studies show that mimicking AtcTPI‐Cys13 oxidation promotes the formation of inactive monomers by reposition residue Phe75 of the neighboring subunit, into a conformation that destabilizes the dimer interface. Mutations in residue AtcTPI‐Cys218 to Asp, Lys, or Tyr generate TPI variants with a decreased enzymatic activity by creating structural modifications in two loops (loop 7 and loop 6) whose integrity is necessary to assemble the active site. In contrast with mutations in residue AtcTPI‐Cys13, mutations in AtcTPI‐Cys218 do not alter the dimeric nature of AtcTPI. Therefore, modifications of residues AtcTPI‐Cys13 and AtcTPI‐Cys218 modulate AtcTPI activity by inducing the formation of inactive monomers and by altering the active site of the dimeric enzyme, respectively. The identity of residue AtcTPI‐Cys218 is conserved in the majority of plant cytosolic TPIs, this conservation and its solvent‐exposed localization make it the most probable target for TPI regulation upon oxidative damage by reactive oxygen species. Our data reveal the structural mechanisms by which S‐glutathionylation protects AtcTPI from irreversible chemical modifications and re‐routes carbon metabolism to the pentose phosphate pathway to decrease oxidative stress. 相似文献
3.
4.
植物戊糖磷酸途径及其两个关键酶的研究进展 总被引:1,自引:0,他引:1
戊糖磷酸途径是植物体中糖代谢的重要途径,主要生理功能是产生供还原性生物合成需要的NADPH,可供核酸代谢的磷酸戊糖以及一些中间产物可参与氨基酸合成和脂肪酸合成等。葡萄糖-6-磷酸脱氢酶和6-磷酸葡萄糖酸脱氢酶是戊糖磷酸途径的两个关键酶,广泛的分布于高等植物的胞质和质体中。本文综述了植物戊糖磷酸途径及其两个关键酶的分子生物学的研究进展,讨论了该途径在植物生长发育和环境胁迫应答中的作用。 相似文献
5.
A dynamic model for plant cell and hairy root primary metabolism is presented. The model includes nutrient uptake (Pi, sugars, nitrogen sources), the glycolysis and pentose phosphate pathways, the TCA cycle, amino acid biosynthesis, respiratory chain, biosynthesis of cell building blocks (structural hexoses, organic acids, lipids, and organic phosphated molecules). The energy shuttles (ATP, ADP) and cofactors (NAD/H, NADP/H) are also included. The model describes the kinetics of 44 biochemical reactions (fluxes) of the primary metabolism of plant cells and includes 41 biochemical species (metabolites, nutrients, biomass components). Multiple Michaelis-Menten type kinetics are used to describe biochemical reaction rates. Known regulatory phenomena on metabolic pathways are included using sigmoid switch functions. A visualization framework showing fluxes and metabolite concentrations over time is presented. The visualization of fluxes and metabolites is used to analyze simulation results from Catharanthus roseus hairy root 50 d batch cultures. The visualization of the metabolic system allows analyzing split ratios between pathways and flux time-variations. For carbon metabolism, the cells were observed to have relatively high and stable fluxes for the central carbon metabolism and low and variable fluxes for anabolic pathways. For phosphate metabolism, a very high free intracellular Pi turnover rate was observed with higher flux variations than for the carbon metabolism. Nitrogen metabolism also exhibited large flux variations. The potential uses of the model are also discussed. 相似文献
6.
Anna Stincone Alessandro Prigione Thorsten Cramer Mirjam M. C. Wamelink Kate Campbell Eric Cheung Viridiana Olin‐Sandoval Nana‐Maria Grüning Antje Krüger Mohammad Tauqeer Alam Markus A. Keller Michael Breitenbach Kevin M. Brindle Joshua D. Rabinowitz Markus Ralser 《Biological reviews of the Cambridge Philosophical Society》2015,90(3):927-963
7.
8.
An integrated functional approach to dissect systemic responses in maize to arbuscular mycorrhizal symbiosis 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Plant, cell & environment》网站下载免费的PDF全文](/ch/ext_images/free.gif)
NINA GERLACH JESSICA SCHMITZ ALEKSANDRA POLATAJKO URTE SCHLÜTER HOLGER FAHNENSTICH SANDRA WITT ALISDAIR R. FERNIE KALLE UROIC UWE SCHOLZ UWE SONNEWALD MARCEL BUCHER 《Plant, cell & environment》2015,38(8):1591-1612
9.
10.
Modelling central metabolic fluxes by constraint‐based optimization reveals metabolic reprogramming of developing Solanum lycopersicum (tomato) fruit
下载免费PDF全文
![点击此处可从《The Plant journal : for cell and molecular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sophie Colombié Christine Nazaret Camille Bénard Benoît Biais Virginie Mengin Marion Solé Laëtitia Fouillen Martine Dieuaide‐Noubhani Jean‐Pierre Mazat Bertrand Beauvoit Yves Gibon 《The Plant journal : for cell and molecular biology》2015,81(1):24-39
Modelling of metabolic networks is a powerful tool to analyse the behaviour of developing plant organs, including fruits. Guided by our current understanding of heterotrophic metabolism of plant cells, a medium‐scale stoichiometric model, including the balance of co–factors and energy, was constructed in order to describe metabolic shifts that occur through the nine sequential stages of Solanum lycopersicum (tomato) fruit development. The measured concentrations of the main biomass components and the accumulated metabolites in the pericarp, determined at each stage, were fitted in order to calculate, by derivation, the corresponding external fluxes. They were used as constraints to solve the model by minimizing the internal fluxes. The distribution of the calculated fluxes of central metabolism were then analysed and compared with known metabolic behaviours. For instance, the partition of the main metabolic pathways (glycolysis, pentose phosphate pathway, etc.) was relevant throughout fruit development. We also predicted a valid import of carbon and nitrogen by the fruit, as well as a consistent CO2 release. Interestingly, the energetic balance indicates that excess ATP is dissipated just before the onset of ripening, supporting the concept of the climacteric crisis. Finally, the apparent contradiction between calculated fluxes with low values compared with measured enzyme capacities suggest a complex reprogramming of the metabolic machinery during fruit development. With a powerful set of experimental data and an accurate definition of the metabolic system, this work provides important insight into the metabolic and physiological requirements of the developing tomato fruits. 相似文献
11.
Responses of the central metabolism in Escherichia coli to phosphoglucose isomerase and glucose-6-phosphate dehydrogenase knockouts
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The responses of Escherichia coli central carbon metabolism to knockout mutations in phosphoglucose isomerase and glucose-6-phosphate (G6P) dehydrogenase genes were investigated by using glucose- and ammonia-limited chemostats. The metabolic network structures and intracellular carbon fluxes in the wild type and in the knockout mutants were characterized by using the complementary methods of flux ratio analysis and metabolic flux analysis based on [U-(13)C]glucose labeling and two-dimensional nuclear magnetic resonance (NMR) spectroscopy of cellular amino acids, glycerol, and glucose. Disruption of phosphoglucose isomerase resulted in use of the pentose phosphate pathway as the primary route of glucose catabolism, while flux rerouting via the Embden-Meyerhof-Parnas pathway and the nonoxidative branch of the pentose phosphate pathway compensated for the G6P dehydrogenase deficiency. Furthermore, additional, unexpected flux responses to the knockout mutations were observed. Most prominently, the glyoxylate shunt was found to be active in phosphoglucose isomerase-deficient E. coli. The Entner-Doudoroff pathway also contributed to a minor fraction of the glucose catabolism in this mutant strain. Moreover, although knockout of G6P dehydrogenase had no significant influence on the central metabolism under glucose-limited conditions, this mutation resulted in extensive overflow metabolism and extremely low tricarboxylic acid cycle fluxes under ammonia limitation conditions. 相似文献
12.
A program implementing a flux model of Escherichia coli metabolism was used to analyze the effects of the addition of amino acids (tryptophan, tyrosine, phenylalanine, leucine, isoleucine, valine, histidine, lysine, threonine, cysteine, methionine, arginine, proline) to minimal medium or media lacking nitrogen, carbon, or both. The overall response of the metabolic system to the addition of various amino acids to the minimal medium is similar. Glycolysis and the synthesis of pyruvate with its subsequent degradation to acetate via acetyl-CoA become more efficient, whereas the fluxes through the pentose phosphate pathway and the TCA cycle decrease. If amino acids are used as the sole source of carbon, nitrogen, or both, the changes in the flux distribution are determined mainly by the carbon limitation. The phosphoenolpyruvate to glucose-6-phosphate flux increases; the flux through the pentose phosphate path is directed towards ribulose-5-phosphate. Other changes are determined by the compounds that are the primary products of catabolism of the added amino acid. 相似文献
13.
Dorion S Clendenning A Jeukens J Salas JJ Parveen N Haner AA Law RD Force EM Rivoal J 《Planta》2012,236(4):1177-1190
Triosephosphate isomerase (TPI, EC 5.3.1.1) catalyzes the interconversion of dihydroxyacetone-P and glyceraldehyde 3-P in the glycolytic pathway. A constitutively expressed antisense construct for cytosolic TPI was introduced into potato (Solanum tuberosum) using Agrobacterium rhizogenes to examine the metabolic effects of a reduction in cytosolic TPI in roots. We obtained a population of transgenic root clones displaying ~36 to 100?% of the TPI activity found in control clones carrying an empty binary vector. Ion exchange chromatography and immunoblot analysis showed that the antisense strategy significantly decreased the cytosolic TPI isoform, while levels of plastidial TPI activity remained apparently unaffected. Transgenic roots were characterized with respect to the activity of glycolytic enzymes, their metabolite contents and carbon fluxes. Metabolite profiling of sugars, organic acids, amino acids and lipids showed elevated levels of sucrose, glucose, fructose, fumarate, isocitrate, 4-aminobutyrate, alanine, glycine, aromatic amino acids and saturated long chain fatty acids in roots containing the lowest TPI activity. Labelings with (14)C-glucose, (14)C-sucrose and (14)C-acetate indicated that a reduction of cytosolic TPI activity in roots increased carbon metabolism through the pentose phosphate pathway, O(2) uptake and catabolism of sucrose to CO(2), and capacity for lipid synthesis. These results demonstrate that a large reduction of cytosolic TPI alters the distribution of carbon in plant primary metabolism. 相似文献
14.
Ludmilla Aristilde Ian A. Lewis Junyoung O. Park Joshua D. Rabinowitz 《Applied and environmental microbiology》2015,81(4):1452-1462
Bacterial metabolism of polysaccharides from plant detritus into acids and solvents is an essential component of the terrestrial carbon cycle. Understanding the underlying metabolic pathways can also contribute to improved production of biofuels. Using a metabolomics approach involving liquid chromatography-mass spectrometry, we investigated the metabolism of mixtures of the cellulosic hexose sugar (glucose) and hemicellulosic pentose sugars (xylose and arabinose) in the anaerobic soil bacterium Clostridium acetobutylicum. Simultaneous feeding of stable isotope-labeled glucose and unlabeled xylose or arabinose revealed that, as expected, glucose was preferentially used as the carbon source. Assimilated pentose sugars accumulated in pentose phosphate pathway (PPP) intermediates with minimal flux into glycolysis. Simultaneous feeding of xylose and arabinose revealed an unexpected hierarchy among the pentose sugars, with arabinose utilized preferentially over xylose. The phosphoketolase pathway (PKP) provides an alternative route of pentose catabolism in C. acetobutylicum that directly converts xylulose-5-phosphate into acetyl-phosphate and glyceraldehyde-3-phosphate, bypassing most of the PPP. When feeding the mixture of pentose sugars, the labeling patterns of lower glycolytic intermediates indicated more flux through the PKP than through the PPP and upper glycolysis, and this was confirmed by quantitative flux modeling. Consistent with direct acetyl-phosphate production from the PKP, growth on the pentose mixture resulted in enhanced acetate excretion. Taken collectively, these findings reveal two hierarchies in clostridial pentose metabolism: xylose is subordinate to arabinose, and the PPP is used less than the PKP. 相似文献
15.
Chinese hamster ovary (CHO) cells are the main platform for production of biotherapeutics in the biopharmaceutical industry. However, relatively little is known about the metabolism of CHO cells in cell culture. In this work, metabolism of CHO cells was studied at the growth phase and early stationary phase using isotopic tracers and mass spectrometry. CHO cells were grown in fed-batch culture over a period of six days. On days 2 and 4, [1,2-13C] glucose was introduced and the labeling of intracellular metabolites was measured by gas chromatography-mass spectrometry (GC–MS) at 6, 12 and 24 h following the introduction of tracer. Intracellular metabolic fluxes were quantified from measured extracellular rates and 13C-labeling dynamics of intracellular metabolites using non-stationary 13C-metabolic flux analysis (13C-MFA). The flux results revealed significant rewiring of intracellular metabolic fluxes in the transition from growth to non-growth, including changes in energy metabolism, redox metabolism, oxidative pentose phosphate pathway and anaplerosis. At the exponential phase, CHO cell metabolism was characterized by a high flux of glycolysis from glucose to lactate, anaplerosis from pyruvate to oxaloacetate and from glutamate to α-ketoglutarate, and cataplerosis though malic enzyme. At the stationary phase, the flux map was characterized by a reduced flux of glycolysis, net lactate uptake, oxidative pentose phosphate pathway flux, and reduced rate of anaplerosis. The fluxes of pyruvate dehydrogenase and TCA cycle were similar at the exponential and stationary phase. The results presented here provide a solid foundation for future studies of CHO cell metabolism for applications such as cell line development and medium optimization for high-titer production of recombinant proteins. 相似文献
16.
Proline metabolism in mammals involves two other amino acids, glutamate and ornithine, and five enzymatic activities, Δ1-pyrroline-5-carboxylate (P5C) reductase (P5CR), proline oxidase, P5C dehydrogenase, P5C synthase and ornithine-δ-aminotransferase
(OAT). With the exception of OAT, which catalyzes a reversible reaction, the other four enzymes are unidirectional, suggesting
that proline metabolism is purpose-driven, tightly regulated, and compartmentalized. In addition, this tri-amino-acid system
also links with three other pivotal metabolic systems, namely the TCA cycle, urea cycle, and pentose phosphate pathway. Abnormalities
in proline metabolism are relevant in several diseases: six monogenic inborn errors involving metabolism and/or transport
of proline and its immediate metabolites have been described. Recent advances in the Human Genome Project, in silico database
mining techniques, and research in dissecting the molecular basis of proline metabolism prompted us to utilize functional
genomic approaches to analyze human genes which encode proline metabolic enzymes in the context of gene structure, regulation
of gene expression, mRNA variants, protein isoforms, and single nucleotide polymorphisms. 相似文献
17.
Metabolic flux distributions of recombinant Escherichia coli BL21 expressing human-like collagen were determined by means of a stoichiometric network and metabolic balancing. At the
batch growth stage, the fluxes of the pentose phosphate pathway were higher than the fluxes of the fed-batch growth phase
and the production stage. After the temperature was increased, there was a substantially elevated energy demand for synthesizing
human-like collagen and heat-shock proteins, which resulted in changes in metabolic fluxes. The activities of the Embden-Meyerhof-Parnas
pathway and the tricarboxylic acid cycle were significantly enhanced, leading to a reduction in the fluxes of the pentose
phosphate pathway and other anabolic pathways. The temperature upshift also caused an increase in NADPH production by isocitrate
dehydrogenase in the tricarboxylic acid cycle. The metabolic model predicted the involvement of a transhydrogenase that generates
additional NADH from NADPH, thereby increasing ATP regeneration in the respiratory chain. These data indicated that the maintenance
energy for cellular activity increased with the increase in biomass in fed-batch culture, and that cell growth and synthesis
of human-like collagen could clearly represent the changes in metabolic fluxes. At the production stage, more NADPH was used
to synthesize human-like collagen than for maintaining cellular activity, cell growth, and cell propagation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Global metabolic profiling of plant cell wall polysaccharide degradation by Saccharophagus degradans
Min Hye Shin Do Yup Lee Kirsten Skogerson Gert Wohlgemuth In‐Geol Choi Oliver Fiehn Kyoung Heon Kim 《Biotechnology and bioengineering》2010,105(3):477-488
Plant cell wall polysaccharides can be used as the main feedstock for the production of biofuels. Saccharophagus degradans 2–40 is considered to be a potent system for the production of sugars from plant biomass due to its high capability to degrade many complex polysaccharides. To understand the degradation metabolism of plant cell wall polysaccharides by S. degradans, the cell growth, enzyme activity profiles, and the metabolite profiles were analyzed by gas chromatography‐time of flight mass spectrometry using different carbon sources including cellulose, xylan, glucose, and xylose. The specific activity of cellulase was only found to be significantly higher when cellulose was used as the sole carbon source, but the xylanase activity increased when xylan, xylose, or cellulose was used as the carbon source. In addition, principal component analysis of 98 identified metabolites in S. degradans revealed four distinct groups that differed based on the carbon source used. Furthermore, metabolite profiling showed that the use of cellulose or xylan as polysaccharides led to increased abundances of fatty acids, nucleotides and glucuronic acid compared to the use of glucose or xylose. Finally, intermediates in the pentose phosphate pathway seemed to be up‐regulated on xylose or xylan when compared to those on glucose or cellulose. Such metabolic responses of S. degradans under plant cell wall polysaccharides imply that its metabolic system is transformed to more efficiently degrade polysaccharides and conserve energy. This study demonstrates that the gas chromatography‐time of flight mass spectrometry‐based global metabolomics are useful for understanding microbial metabolism and evaluating its fermentation characteristics. Biotechnol. Bioeng. 2010; 105: 477–488. © 2009 Wiley Periodicals, Inc. 相似文献
19.
The synthesis of human superoxide dismutase (SOD) in batch cultures of a Saccharomyces cerevisiae strain using a glucose-limited minimal medium was studied through metabolic flux analysis. A stoichiometric model was built, which included 78 reactions, according to metabolic pathways operative in these strains during respirofermentative and oxidative metabolism. It allowed calculation of the distribution of metabolic fluxes during diauxic growth on glucose and ethanol. Fermentation profiles and metabolic fluxes were analyzed at different phases of diauxic growth for the recombinant strain (P+) and for its wild type (P-). The synthesis of SOD by the strain P+ resulted in a decrease in specific growth rate of 34 and 54% (growth on glucose and ethanol respectively) in comparison to the wild type. Both strains exhibited similar flux of glucose consumption and ethanol synthesis but important differences in carbon distribution with biomass/substrate yields and ATP production 50% higher in P-. A higher contribution of fermentative metabolism, with 64% of the energy produced at the phosphorylation level, was observed during SOD production. The flux of precursors to amino acids and nucleotides was higher in the recombinant strain, in agreement with the higher total RNA and protein levels. Lower specific growth rates in strain P+ appear to be related to the decrease in the rate of synthesis of nonrecombinant protein, as well as a decrease in the activities of the pentose phosphate (PP) pathway and TCA cycle. A very different way of entry into the stationary phase was observed for each strain: in the wild-type strain most metabolic fluxes decreased and fluxes related to energy reserve synthesis increased, while in the P+ strain the flux of 22 reactions (including PP pathway and amino acids biosynthesis) related to SOD production increased their fluxes. Changes in SOD production rates at different physiological states appear to be related to the differences in building blocks availability between respirofermentative and oxidative metabolism. Using the present expression system, ideal conditions for SOD synthesis are represented by either active growth during respirofermentative metabolism or transition from a growing to a nongrowing state. An increase in SOD flux could be achieved using an expression system nonassociated to growth and potentially eliminating part of the metabolic burden. 相似文献
20.
E. N. Krasil’nikova L. M. Zakharchuk M. A. Egorova T. I. Bogdanova A. E. Zhuravleva I. A. Tsaplina 《Microbiology》2010,79(2):147-152
A comparative study of the activities of the enzymes of carbon metabolism from the cells of moderately thermophilic chemolithotrophic
bacteria Sulfobacillus sibiricus (strains N1 and SSO) and Sulfobacillus thermosulfidooxidans subsp. asporogenes (strain 41) was carried out grown in a high layer of medium without forced aeration and cells grown with intense aeration.
Limited air access to the growing S. sibiricus N1 cells resulted in switching from the pentose phosphate pathway of glucose metabolism to the Entner-Doudoroff pathway while
the Embden-Meyerhof-Parnas pathway persisted. Irrespective of the level of the aeration, in the cells of S. sibiricus SSO and S. thermosulfidooxidans subsp. asporogenes 41, degradation of the glucose occurred via the Entner-Doudoroff and pentose phosphate metabolic pathways, respectively,
as well as via the Embden-Meyerhof-Parnas pathway. Prolonged growth of S. sibiricus, strains N1 and SSO, in a high layer of the medium without forced aeration led to the repression of synthesis of most of
the tricarboxylic acid cycle (TCA cycle) enzymes, in particular dehydrogenases, as well as of some carboxylases including
RuBisCO. The traits of carbon metabolism in various strains of Sulfobacillus under conditions of oxygen deficiency are discussed. 相似文献