Identification of non-equilibrium glycolytic reactions in suspension-cultured plant cells

Kubota, K; Ashihara, Hiroshi

doi:10.1016/0304-4165(90)90025-r

Cited by 37 publications

(28 citation statements)

References 22 publications

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“…The mass to action ratio measured for the substrates and products of PFP in plants is close to its K eq value (Kubota and Ashihara, 1990). This implies that in the plant cytosol, the direction of the reaction may be determined by the [PP i ] to [P i ] ratio and that the PP i formed at the expense of F1,6BP could ultimately be used to pump H ϩ across the tonoplast membrane as follows:…”

supporting

confidence: 52%

“…The aim of this study was to evaluate whether the maize (Zea mays) root H ϩ -PPase is able to bind and hydrolyze the PP i formed by Reaction 1 catalyzed by PFP in vitro under conditions that mimic the concentrations of F1,6BP, P i , Mg 2ϩ , F2,6BP, and F6P found in the plant cell cytosol (Rebeille et al, 1983;Ukaji and Ashihara, 1987;Weiner et al, 1987;Kubota and Ashihara, 1990;Davies et al, 1993;Stitt, 1998; Table I). Here, we show that the affinity of maize root H ϩ -PPase for PP i under these conditions is sufficient to shift Reaction 1 toward PP i formation, making it possible to build up a proton gradient in the tonoplast even in the presence of very low amounts of PFP.…”

mentioning

confidence: 99%

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Proton Transport in Maize Tonoplasts Supported by Fructose-1,6-Bisphosphate Cleavage. Pyrophosphate-Dependent Phosphofructokinase as a Pyrophosphate-Regenerating System

et al. 2003

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The energy derived from pyrophosphate (PP i ) hydrolysis is used to pump protons across the tonoplast membrane, thus forming a proton gradient. In a plant's cytosol, the concentration of PP i varies between 10 and 800 m, and the PP i concentration needed for one-half maximal activity of the maize (Zea mays) root tonoplast H ϩ -pyrophosphatase is 30 m. In this report, we show that the H ϩ -pyrophosphatase of maize root vacuoles is able to hydrolyze PP i (Reaction 2) formed by Reaction 1, which is catalyzed by PP i -dependent phosphofructokinase (PFP):Fructose-1,6-bisphosphate (F1,6BP) ϩ P i 7 PP i ϩFructose-6-phosphate (F6 P) (reaction 1)During the steady state, one-half of the inorganic phosphate released (Reaction 4) is ultimately derived from F1,6BP, whereas PFP continuously regenerates the pyrophosphate (PP i ) hydrolyzed. A proton gradient (⌬pH) can be built up in tonoplast vesicles using PFP as a PP i -regenerating system. The ⌬ pH formed by the H ϩ -pyrophosphatase can be dissipated by addition of 20 mm F6P, which drives Reaction 1 to the left and decreases the PP i available for the H ϩ -pyrophosphatase. The maximal ⌬ pH attained by the pyrophosphatase coupled to the PFP reaction can be maintained by PFP activities far below those found in higher plants tissues.

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supporting

confidence: 52%

mentioning

confidence: 99%

Proton Transport in Maize Tonoplasts Supported by Fructose-1,6-Bisphosphate Cleavage. Pyrophosphate-Dependent Phosphofructokinase as a Pyrophosphate-Regenerating System

et al. 2003

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“…inhibitory to the opposite reaction (gluconeogenesis) using PPi: Fru-6-P phosphotransferase purified from potato (Solanum tuberosum) tuber. The concentrations of the reactants are close to equilibrium in plant cytoplasm (Kubota and Ashihara, 1990); therefore, the reaction is readily reversible if the concentrations change.…”

Section: Discussionmentioning

confidence: 99%

Keep an Eye on PPi: The Vacuolar-Type H+-Pyrophosphatase Regulates Postgerminative Development inArabidopsis

et al. 2011

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Postgerminative growth of seed plants requires specialized metabolism, such as gluconeogenesis, to support heterotrophic growth of seedlings until the functional photosynthetic apparatus is established. Here, we show that the Arabidopsis thaliana fugu5 mutant, which we show to be defective in AVP1 (vacuolar H + -pyrophosphatase), failed to support heterotrophic growth after germination. We found that exogenous supplementation of Suc or the specific removal of the cytosolic pyrophosphate (PPi) by the heterologous expression of the cytosolic inorganic pyrophosphatase1 (IPP1) gene from budding yeast (Saccharomyces cerevisiae) rescued fugu5 phenotypes. Furthermore, compared with the wild-type and AVP1 Pro :IPP1 transgenic lines, hypocotyl elongation in the fugu5 mutant was severely compromised in the dark but recovered upon exogenous supply of Suc to the growth media. Measurements revealed that the peroxisomal b-oxidation activity, dry seed contents of storage lipids, and their mobilization were unaffected in fugu5. By contrast, fugu5 mutants contained ;2.5-fold higher PPi and ;50% less Suc than the wild type. Together, these results provide clear evidence that gluconeogenesis is inhibited due to the elevated levels of cytosolic PPi. This study demonstrates that the hydrolysis of cytosolic PPi, rather than vacuolar acidification, is the major function of AVP1/FUGU5 in planta. Plant cells optimize their metabolic function by eliminating PPi in the cytosol for efficient postembryonic heterotrophic growth.

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“…By thermodynamics, PPi could work as an energy donor if present at relatively high concentration (Weiner et al, 1987). High PPi levels have been found in the cytosolic compartment of leaves (Weiner et al, 1987), in plant cell cultures (Dancer et al, 1990;Kubota and Ashihara, 1990), as well as in developing seeds of Arabidopsis (Gibon et al, 2002) and pea (Pisum sativum; Edwards et al, 1984). Therefore, specifically in the cytosol, PPi might be used as an energy metabolite and couple anabolism to catabolism.…”

Section: Genetic Control Of Tradeoff By Transcription Factorsmentioning

confidence: 99%

Predictive Modeling of Biomass Component Tradeoffs in Brassica napus Developing Oilseeds Based on in Silico Manipulation of Storage Metabolism

Schwender

Hay

2012

Plant Physiology

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Seed oil content is a key agronomical trait, while the control of carbon allocation into different seed storage compounds is still poorly understood and hard to manipulate. Using bna572, a large-scale model of cellular metabolism in developing embryos of rapeseed (Brassica napus) oilseeds, we present an in silico approach for the analysis of carbon allocation into seed storage products. Optimal metabolic flux states were obtained by flux variability analysis based on minimization of the uptakes of substrates in the natural environment of the embryo. For a typical embryo biomass composition, flux sensitivities to changes in different storage components were derived. Upper and lower flux bounds of each reaction were categorized as oil or protein responsive. Among the most oil-responsive reactions were glycolytic reactions, while reactions related to mitochondrial ATP production were most protein responsive. To assess different biomass compositions, a tradeoff between the fractions of oil and protein was simulated. Based on flux-bound discontinuities and shadow prices along the tradeoff, three main metabolic phases with distinct pathway usage were identified. Transitions between the phases can be related to changing modes of the tricarboxylic acid cycle, reorganizing the usage of organic carbon and nitrogen sources for protein synthesis and acetylcoenzyme A for cytosol-localized fatty acid elongation. The phase close to equal oil and protein fractions included an unexpected pathway bypassing a-ketoglutarate-oxidizing steps in the tricarboxylic acid cycle. The in vivo relevance of the findings is discussed based on literature on seed storage metabolism.

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Identification of non-equilibrium glycolytic reactions in suspension-cultured plant cells

Cited by 37 publications

References 22 publications

Proton Transport in Maize Tonoplasts Supported by Fructose-1,6-Bisphosphate Cleavage. Pyrophosphate-Dependent Phosphofructokinase as a Pyrophosphate-Regenerating System

Proton Transport in Maize Tonoplasts Supported by Fructose-1,6-Bisphosphate Cleavage. Pyrophosphate-Dependent Phosphofructokinase as a Pyrophosphate-Regenerating System

Keep an Eye on PPi: The Vacuolar-Type H+-Pyrophosphatase Regulates Postgerminative Development inArabidopsis

Predictive Modeling of Biomass Component Tradeoffs in Brassica napus Developing Oilseeds Based on in Silico Manipulation of Storage Metabolism

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