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Xu Y, Schmiege SC, Sharkey TD. The oxidative pentose phosphate pathway in photosynthesis: a tale of two shunts. THE NEW PHYTOLOGIST 2024; 242:2453-2463. [PMID: 38567702 DOI: 10.1111/nph.19730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 03/17/2024] [Indexed: 05/24/2024]
Abstract
CO2 release in the light (RL) and its presumed source, oxidative pentose phosphate pathways, were found to be insensitive to CO2 concentration. The oxidative pentose phosphate pathways form glucose 6-phosphate (G6P) shunts that bypass the nonoxidative pentose phosphate reactions of the Calvin-Benson cycle. Using adenosine diphosphate glucose and uridine diphosphate glucose as proxies for labeling of G6P in the stroma and cytosol respectively, it was found that only the cytosolic shunt was active. Uridine diphosphate glucose, a proxy for cytosolic G6P, and 6-phosphogluconate (6PG) were significantly less labeled than Calvin-Benson cycle intermediates in the light. But ADP glucose, a proxy for stromal G6P, is labeled to the same degree as Calvin-Benson cycle intermediates and much greater than 6PG. A metabolically inert pool of sedoheptulose bisphosphate can slowly equilibrate keeping the label in sedoheptulose lower than in other stromal metabolites. Finally, phosphorylation of fructose 6-phosphate (F6P) in the cytosol can allow some unlabeled carbon in cytosolic F6P to dilute label in phosphenolpyruvate. The results clearly show that there is oxidative pentose phosphate pathway activity in the cytosol that provides a shunt around the nonoxidative pentose phosphate pathway reactions of the Calvin-Benson cycle and is not strongly CO2-sensitive.
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Affiliation(s)
- Yuan Xu
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
| | - Stephanie C Schmiege
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
- Department of Biology, Western University, London, ON, N6A 5B7, Canada
| | - Thomas D Sharkey
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
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Rye PT, LaMarr WA. Measurement of glycolysis reactants by high-throughput solid phase extraction with tandem mass spectrometry: Characterization of pyrophosphate-dependent phosphofructokinase as a case study. Anal Biochem 2015; 482:40-7. [PMID: 25849585 DOI: 10.1016/j.ab.2015.03.029] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 02/26/2015] [Accepted: 03/28/2015] [Indexed: 01/28/2023]
Abstract
Glycolysis is a 10-step metabolic pathway involved in producing cellular energy. Many tumors exhibit accelerated glycolytic rates, and enzymes that participate in this pathway are focal points of cancer research. Here, a novel method for the measurement of glycolysis reactants from in vitro samples is presented. Fast and direct measurement is achieved by an automated system that couples on-line solid phase extraction (SPE) with tandem mass spectrometry (MS/MS). The single analytical method enables multiple reactants to be measured concurrently, sustains a cycle time of 8s, and permits the measurement of up to 10,000 samples per day. Concentration-response curves were conducted using standards for 10 metabolic intermediates, and the results demonstrate that the detection strategy has excellent sensitivity (average limit of detection = 5.4 nM), dynamic range (nanomolar to micromolar), and linear response (average R(2) = 0.998). To test the analysis method on reactions, pyrophosphate-dependent phosphofructokinase (PPi-PFK) was used as a model system. Data that corroborate the activation and inhibition of PPi-PFK are presented, and the ways in which SPE-MS/MS simplifies experimental design and interpretation are highlighted. In summary, the method for measuring metabolic intermediates described here demonstrates unprecedented speed, performance, and versatility.
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Affiliation(s)
- Peter T Rye
- Agilent Technologies, Wakefield, MA 01880, USA.
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Groenewald JH, Botha FC. Molecular and kinetic characterisation of sugarcane pyrophosphate: fructose-6-phosphate 1-phosphotransferase and its possible role in the sucrose accumulation phenotype. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:517-525. [PMID: 32689381 DOI: 10.1071/fp06213] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Accepted: 03/29/2007] [Indexed: 06/11/2023]
Abstract
The amount of pyrophosphate: fructose-6-phosphate 1-phosphotransferase (PFP) activity in sugarcane internodal tissue is inversely correlated with sucrose content. To help elucidate this apparent role of PFP in sucrose accumulation in sugarcane we have determined its molecular and kinetic properties. Sugarcane PFP was purified 285-fold to a final specific activity of 4.23 µmol min-1 mg-1 protein. It contained two polypeptides of 63.2 and 58.0 kDa respectively, at near equal amounts that cross-reacted with potato PFP-α and -β antiserum. In gel filtration analyses the native enzyme eluted in three peaks of 129, 245 and 511 kDa, corresponding to dimeric, tetrameric and octameric forms, respectively and fructose 2,6-bisphosphate (Fru 2,6-P2) influenced this aggregation state. Both the glycolytic (forward) and gluconeogenic (reverse) reactions had relative broad pH optima between pH 6.7 and 8.0. The Fru 2,6-P2 saturation curves were hyperbolic with approximate Ka values of 69 and 82 nm for the forward and reverse reactions, respectively. The enzyme showed hyperbolic saturation curves for all its substrates with Km values comparable with that of other plant PFP, i.e. 150, 37, 39 and 460 µM for fructose 6-phosphate, inorganic pyrophosphate, fructose 1,6-bisphosphate and inorganic phosphate, respectively. Sugarcane PFP's molecular and kinetic characteristics differed slightly from that of other plant PFP in that: (i) Fru 2,6-P2 directly induced the octameric state from the dimeric state; (ii) Fru 2,6-P2 shifted the pH optimum for the forward reaction to a slightly more basic pH; and (iii) Fru 2,6-P2 increased the Vmax for the forward and reverse reactions by similar amounts.
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Affiliation(s)
- Jan-Hendrik Groenewald
- Institute for Plant Biotechnology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
| | - Frederik Coenraad Botha
- Institute for Plant Biotechnology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa
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Van Schaftingen E. Fructose 2,6-bisphosphate. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2006; 59:315-95. [PMID: 3028056 DOI: 10.1002/9780470123058.ch7] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Alves AM, Euverink GJ, Santos H, Dijkhuizen L. Different physiological roles of ATP- and PP(i)-dependent phosphofructokinase isoenzymes in the methylotrophic actinomycete Amycolatopsis methanolica. J Bacteriol 2001; 183:7231-40. [PMID: 11717283 PMCID: PMC95573 DOI: 10.1128/jb.183.24.7231-7240.2001] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cells of the actinomycete Amycolatopsis methanolica grown on glucose possess only a single, exclusively PP(i)-dependent phosphofructokinase (PP(i)-PFK) (A. M. C. R. Alves, G. J. W. Euverink, H. J. Hektor, J. van der Vlag, W. Vrijbloed, D.H.A. Hondmann, J. Visser, and L. Dijkhuizen, J. Bacteriol. 176:6827-6835, 1994). When this methylotrophic bacterium is grown on one-carbon (C(1)) compounds (e.g., methanol), an ATP-dependent phosphofructokinase (ATP-PFK) activity is specifically induced, completely replacing the PP(i)-PFK. The two A. methanolica PFK isoenzymes have very distinct functions, namely, in the metabolism of C(6) and C(1) carbon substrates. This is the first report providing biochemical evidence for the presence and physiological roles of PP(i)-PFK and ATP-PFK isoenzymes in a bacterium. The novel ATP-PFK enzyme was purified to homogeneity and characterized in detail at the biochemical and molecular levels. The A. methanolica ATP-PFK and PP(i)-PFK proteins possess a low level of amino acid sequence similarity (24%), clearly showing that the two proteins are not the result of a gene duplication event. PP(i)-PFK is closely related to other (putative) actinomycete PFK enzymes. Surprisingly, the A. methanolica ATP-PFK is most similar to ATP-PFK from the protozoon Trypanosoma brucei and PP(i)-PFK proteins from the bacteria Borrelia burgdorferi and Treponema pallidum, both spirochetes, very distinct from actinomycetes. The data thus suggest that A. methanolica obtained the ATP-PFK-encoding gene via a lateral gene transfer event.
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Affiliation(s)
- A M Alves
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, 9751 NN Haren, The Netherlands
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Gancedo JM. Metabolite-mediated catalyst conversion of PFK and PFP: can PFK really be converted to PFP? FEBS Lett 2001. [DOI: 10.1016/0014-5793(84)80770-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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A novel pyrophosphate fructose-6-phosphate 1-phosphotransferase from carrot roots Relation to PFK from the same source. FEBS Lett 2001. [DOI: 10.1016/0014-5793(88)80521-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Alves AM, Meijer WG, Vrijbloed JW, Dijkhuizen L. Characterization and phylogeny of the pfp gene of Amycolatopsis methanolica encoding PPi-dependent phosphofructokinase. J Bacteriol 1996; 178:149-55. [PMID: 8550409 PMCID: PMC177632 DOI: 10.1128/jb.178.1.149-155.1996] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The actinomycete Amycolatopsis methanolica employs a PPi-dependent phosphofructokinase (PPi-PFK) (EC 2.7.1.90) with biochemical characteristics similar to those of both ATP- and PPi-dependent enzymes during growth on glucose. A 2.3-kb PvuII fragment hybridizing to two oligonucleotides based on the amino-terminal amino acid sequence of PPi-PFK was isolated from a genomic library of A. methanolica. Nucleotide sequence analysis of this fragment revealed the presence of an open reading frame encoding a protein of 340 amino acids with a high degree of similarity to PFK proteins. Heterologous expression of this open reading frame in Escherichia coli gave rise to a unique 45-kDa protein displaying a high level of PPi-PFK activity. The open reading frame was therefore designated pfp, encoding the PPi-PFK of A. methanolica. Upstream and transcribed divergently from pfp, a partial open reading frame (aroA) similar to 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase-encoding genes was identified. The partial open reading frame (chiA) downstream from pfp was similar to chitinase genes from Streptomyces species. A phylogenetic analysis of the ATP- and PPi-dependent proteins showed that PPi-PFK enzymes are monophyletic, suggesting that the two types of PFK evolved from a common ancestor.
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Affiliation(s)
- A M Alves
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Haren, The Netherlands
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Corbineau F, Carmignac DF, Gahan PB, Maple AJ. Glycolytic activity in embryos of Pisum sativum and of non-dormant or dormant seeds of Avena sativa L. expressed through activities of PFK and PPi-PFK. HISTOCHEMISTRY 1989; 90:359-64. [PMID: 2541117 DOI: 10.1007/bf00508313] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A quantitative cytochemical assay for PPi-PFK activity in the presence of Fru-2,6-P2 is described along with its application to determine levels of activity in embryos of Pisum sativum and Avena sativa. The activity of ATP-PFK has also been studied in parallel as have PFK activities during the switch from dormant to non-dormant embryos in Avena sativa. PPi-PFK activity has been demonstrated in all tissues of Pisum sativum embryos and of Avena sativa embryos including the scutellum and the aleurone layers. The PPi-PFK activity was greater than that of ATP-PFK in both dormant and non-dormant seeds though with only marginally more activity in the dormant as opposed to the non-dormant state.
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Affiliation(s)
- F Corbineau
- Laboratoire de Physiologie des Organes Végétaux après Récolte, C.N.R.S., Meudon, France
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Kruger NJ, Dennis DT. Molecular properties of pyrophosphate:fructose-6-phosphate phosphotransferase from potato tuber. Arch Biochem Biophys 1987; 256:273-9. [PMID: 3038023 DOI: 10.1016/0003-9861(87)90446-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Pyrophosphate:fructose-6-phosphate phosphotransferase (PFP) from potato tubers has been purified to homogeneity. The enzyme contains two polypeptides with apparent relative molecular mass (Mr) values of 65,000 and 60,000. These polypeptides give different peptide fragments after limited proteolytic digestion. Antibodies raised against each polypeptide separately are specific for that polypeptide, but both antisera are capable of immunoprecipitating native PFP activity. These antibodies also recognize similar pairs of polypeptides in a range of other plant tissues that contain PFP activity. Based on gel filtration, the Mr value of potato tuber PFP is 265,000. This suggests that the enzyme is a heterotetramer composed of two polypeptides with Mr values of 65,000 and 60,000. In the presence of pyrophosphate, potato PFP dissociates into a 130,000 dimer.
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Macdonald FD, Preiss J. The subcellular location and characteristics of pyrophosphate-fructose-6-phosphate 1-phosphotransferase from suspension-cultured cells of soybean. PLANTA 1986; 167:240-245. [PMID: 24241857 DOI: 10.1007/bf00391421] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/1985] [Accepted: 10/24/1985] [Indexed: 06/02/2023]
Abstract
The cytoplasm was identified as the probable location of pyrophosphate-fructose-6-phosphate 1-phosphotransferase (EC 2.7.1.90) in suspension-cultured cells of soybean (Glycine max L.). The characteristics of the partially purified enzyme were investigated. The activity was strongly dependent on the presence of fructose 2,6-bisphosphate and this activator exerted its effects through a dramatic increase in the affinity of the enzyme for its substrates, fructose 6-phosphate and inorganic pyrophosphate. Saturation curves for all substrates were hyperbolic. The apparent molecular weight of the partially purified enzyme was 183000 by gel filtration chromatography and 128000 by sucrose-density-gradient centrifugation. The activation by fructose 2,6-bisphosphate was not accompanied by any measurable change in molecular weight. The possible role of this enzyme in the metabolism of non-photosynthetic sink tissues is discussed.
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Affiliation(s)
- F D Macdonald
- Department of Biochemistry and Biophysics, University of California, 95616, Davis, CA, USA
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Crawford NA, Yee BC, Hutcheson SW, Wolosiuk RA, Buchanan BB. Enzyme regulation in C4 photosynthesis: purification, properties, and activities of thioredoxins from C4 and C3 plants. Arch Biochem Biophys 1986; 244:1-15. [PMID: 3004333 DOI: 10.1016/0003-9861(86)90088-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Procedures are described for the purification to homogeneity of chloroplast thioredoxins f and m from leaves of corn (Zea mays, a C4 plant) and spinach (Spinacea oleracea, a C3 plant). The C3 and C4f thioredoxins were similar immunologically and biochemically, but differed in certain of their physiochemical properties. The f thioredoxins from the two species were capable of activating both NADP-malate dehydrogenase (EC 1.1.1.37) and fructose-1,6-bisphosphatase (EC 3.1.3.11) when tested in standard thioredoxin assays. Relative to its spinach counterpart, corn thioredoxin f showed a greater molecular mass (15.0-16.0 kDa vs 10.5 kDa), lower isoelectric point (ca. 5.2 vs 6.0), and lower ability to form a stable noncovalent complex with its target fructose bisphosphatase enzyme. The C3 and C4 m thioredoxins were similar in their specificity (ability to activate NADP-malate dehydrogenase, and not fructose-1,6-bisphosphatase) and isoelectric points (ca. 4.8), but differed slightly in molecular mass (13.0 kDa for spinach vs 13.5 kDa for corn) and substantially in their immunological properties. Results obtained in conjunction with these studies demonstrated that the thioredoxin m-linked activation of NADP-malate dehydrogenase in selectively enhanced by the presence of halide ions (e.g., chloride) and by an organic solvent (e.g., 2-propanol). The results suggest that in vivo NADP-malate dehydrogenase interacts with thylakoid membranes and is regulated to a greater extent by thioredoxin m than thioredoxin f.
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Pollack JD, Williams MV. PPi-dependent phosphofructotransferase (phosphofructokinase) activity in the mollicutes (mycoplasma) Acholeplasma laidlawii. J Bacteriol 1986; 165:53-60. [PMID: 3001032 PMCID: PMC214369 DOI: 10.1128/jb.165.1.53-60.1986] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
A PPi-dependent phosphofructotransferase (PPi-fructose 6-phosphate 1-phosphotransferase, EC 2.7.1.90) which catalyzes the conversion of fructose 6 phosphate (F-6-P) to fructose 1,6-bisphosphate (F-1, 6-P2) was isolated from a cytoplasmic fraction of Acholeplasma laidlawii B-PG9 and partially purified (430-fold). PPi was required as the phosphate donor. ATP, dATP, CTP, dCTP, GTP, dGTP, UTP, dUTP, ITP, TTP, ADP, or Pi could not substitute for PPi. The PPi-dependent reaction (2.0 mM PPi) was not altered in the presence of any of these nucleotides (2.0 mM) or in the presence of smaller (less than or equal to 300 microM) amounts of fructose 2,6-bisphosphate, (NH4)2SO4, AMP, citrate, GDP, or phosphoenolpyruvate. Mg2+ and a pH of 7.4 were required for maximum activity. The partially purified enzyme in sucrose density gradient experiments had an approximate molecular weight of 74,000 and a sedimentation coefficient of 6.7. A second form of the enzyme (molecular weight, 37,000) was detected, although in relatively smaller amounts, by using Blue Sepharose matrix when performing electrophoresis experiments. The back reaction, F-1, 6-P2 to F-6-P, required Pi; arsenate could substitute for Pi, but not PPi or any other nucleotide tested. The computer-derived kinetic constants (+/- standard deviation) for the reaction in the PPi-driven direction of F-1, 6-P2 were as follows: v, 38.9 +/- 0.48 mM min-1; Ka(PPi), 0.11 +/- 0.04 mM; Kb(F-6-P), 0.65 +/- 0.15 mM; and Kia(PPi), 0.39 +/- 0.11 mM. A. laidlawii B-PG9 required PPi not only for the PPi-phosphofructotransferase reaction which we describe but also for purine nucleoside kinase activity. a dependency unknown in any other organism. In A. laidlawii B-PG9, the PPi requirement may be met by reactions in this organism already known to synthesize PPi (e.g., dUTPase and purine nucleobase phosphoribosyltransferases). In almost all other cells, the conversion of F-6-P to F-1,6-P2 is ATP dependent, and the reaction is generally considered to be the rate-limiting step of glycolysis. The ability of A. laidlawii B-PG9 and one other acholeplasma to use PPi instead of ATP as an energy source may offer these cytochrome-deficient organisms some metabolic advantage and may represent a conserved metabolic remnant of an earlier evolutionary process.
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Smith AM. Capacity for fermentation in roots and Rhizobium nodules of Pisum sativum L. PLANTA 1985; 166:264-270. [PMID: 24241442 DOI: 10.1007/bf00397358] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/1985] [Accepted: 04/16/1985] [Indexed: 06/02/2023]
Abstract
The aim of this work was to compare the capacities for fermentation and synthesis of malate from phosphoenolpyruvate in roots and Rhizobium nodules of Pisum sativum. The nodules and the cortices and apices of roots had similar activities of glycolytic enzymes and enzymes of ethanolic and lactic fermentation when expressed on a protein basis. The activity of phosphoenolpyruvate carboxylase was similar in nodules and apices, and three to four fold lower in cortices. All three tissues had very high activities of malate dehydrogenase, significant activity of NADP-malic enzyme, and no detectable activity of phosphoenolpyruvate carboxykinase. These results do not support the belief that nodules have a substantially greater capacity to convert phosphoenolpyruvate to malate than roots, or that there are major qualitative differences in the pathways of fermentation of nodules and roots.
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Affiliation(s)
- A M Smith
- John Innes Institute, Colney Lane, NR4 7UH, Norwich, UK
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Champigny ML. Regulation of photosynthetic carbon assimilation at the cellular level: a review. PHOTOSYNTHESIS RESEARCH 1985; 6:273-286. [PMID: 24442925 DOI: 10.1007/bf00049283] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/1984] [Revised: 10/22/1984] [Indexed: 06/03/2023]
Abstract
In green leaves and a number of algae, photosynthetically derived carbon is ultimately converted into two carbohydrate end-products, sucrose and starch. Drainage of carbon from the Calvin cycle proceeds via triose phosphate, fructose 6-phosphate and glycollate. Gluconeogenesis in photosynthetic cells is controlled by light, inorganic phosphate and phosphorylated sugars. Light stimulates the production of dihydroxyacetone phosphate, the initial substrate for sucrose and starch synthesis, and inhibits the degradative pathways in the chloroplast. Phosphate inactivates reactions of synthesis and activates reactions of degradation. Among the phosphorylated sugars a special role is allocated to fructose 2,6-bisphosphate, which is present in the cytoplasm at very low concentrations and inhibits sucrose synthesis directly by inactivating pyrophosphatedependent phosphofructokinase. The synthesis of sucrose plays a central role in the partitioning of photosynthetic carbon. The cytoplasmic enzymes, fructose bisphosphate phosphatase and sucrose phosphate synthase are likely key points of regulation. The regulation is carried out by several effector metabolites. Fructose 2,6-bisphosphate is likely to be the main coordinator of the rate of sucrose synthesis, hence of photosynthetic carbon partitioning between sucrose and starch.
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Affiliation(s)
- M L Champigny
- Photosynthèse et Métabolisme (CNRS, LA 040), Université de Paris-Sud, F 91405, ORSAY Cedex, France
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Kruger NJ, Dennis DT. A source of apparent pyrophosphate:fructose 6-phosphate phosphotransferase activity in rabbit muscle phosphofructokinase. Biochem Biophys Res Commun 1985; 126:320-6. [PMID: 2982370 DOI: 10.1016/0006-291x(85)90608-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
In the presence of UDPglucose, rabbit muscle phosphofructokinase appeared to use PPi as a phosphoryl donor, as reported previously (Biochem. Biophys. Res. Commun. 121, 842-847). This apparent activity was due to conversion of UDPglucose and PPi to glucose 1-phosphate and UTP, the latter being metabolized by phosphofructokinase. Auxiliary enzymes used in the assays were contaminated by UDPglucose pyrophosphorylase. This contamination was sufficient to account for, and had similar properties to, the apparent PPi-dependent activity. Without auxiliary enzymes phosphofructokinase could not use PPi. These findings indicate that the apparent interconversion of phosphofructokinase and PPi:fructose 6-phosphate phosphotransferase must be re-assessed.
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Cseke C, Balogh A, Wong J, Buchanan B, Stitt M, Herzog B, Heldt H. Fructose 2,6-bisphosphate: a regulator of carbon processing in leaves. Trends Biochem Sci 1984. [DOI: 10.1016/0968-0004(84)90284-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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