Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.1.2.13 (aldolase)
3,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To test the hypothesis that the contribution of phosphoribulokinase (PRK) to the control of photosynthesis changes depending on the light environment of the plant, the response of transgenic tobacco (Nicotiana tabacum L.) transformed with antisense PRK constructs to irradiance was determined. In plants grown under low irradiance (330 micromol m(-2) s(-1)) steady-state photosynthesis was limited in plants with decreased PRK activity upon exposure to higher irradiance, with a control coefficient of PRK for CO2 assimilation of 0.25 at and above 800 micromol m(-2) s(-1). The flux control coefficient of PRK for steady-state CO2 assimilation was zero, however, at all irradiances in plant material grown at 800 micromol m(-2) s(-1) and in plants grown in a glasshouse during mid-summer (alternating shade and sun 300-1600 micromol m(-2) s(-1)). To explain these differences between plants grown under low and high irradiances, Calvin cycle enzyme activities and metabolite content were determined. Activities of PRK and other non-equilibrium Calvin cycle enzymes fructose-1,6-bisphosphatase, sedoheptulose-1,7-bisphosphatase and ribulose-1,5-bisphosphate carboxylase-oxygenase were twofold higher in plants grown at 800 micromol m(-2) s(-1) or in the glasshouse than in plants grown at 330 micromol m(-2) s(-1). Activities of equilibrium enzymes transketolase, aldolase, ribulose-5-phosphate epimerase and isomerase were very similar under all growth irradiances. The flux control coefficient of 0.25 in plants grown at 330 micromol m(-2) s(-1) can be explained because low ribulose-5-phosphate content in combination with low PRK activity limits the synthesis of ribulose-1,5-bisphosphate. This limitation is overcome in high-light-grown plants because of the large relative increase in activities of sedoheptulose-1,7-bisphosphatase and fructose-1,6-bisphosphatase under these conditions, which facilitates the synthesis of larger amounts of ribulose-5-phosphate. This potential limitation will have maintained evolutionary selection pressure for high concentrations of PRK within the chloroplast.
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PMID:Decrease of phosphoribulokinase activity by antisense RNA in transgenic tobacco: definition of the light environment under which phosphoribulokinase is not in large excess. 1092 11

Low temperature inhibits sucrose synthesis, leading to a phosphate-limitation of photosynthesis. We have used the Arabidopsis pho1-2 and pho2-1 mutants with decreased and increased shoot phosphate, respectively, to investigate whether low phosphate triggers cold acclimatization of photosynthetic carbon metabolism. Wild-type Arabidopsis, pho1-2 and pho2-1 were grown at 23 degrees C and transferred to 5 degrees C to investigate acclimatization in pre-existing leaves and in new leaves developing at 5 degrees C. The development of frost tolerance and the accumulation of proline and sugars was unaltered or improved in pho1-2, and impaired in pho2-1. Sucrose phosphate synthase and cytoplasmic fructose-1,6-bisphosphatase activity and protein increase after transfer to 5 degrees C. This increase was accentuated in pho1-2 and attenuated in pho2-1. RBCS and LHCB2 transcript levels decrease in pre-formed wild-type leaves after transfer to 5 degrees C and recover in new leaves that develop at 5 degrees C. The initial decrease was attenuated in pho1-2, and accentuated in pho2-1, where the recovery in new leaves was also suppressed. Rubisco activity increased in wild-type leaves that developed at 5 degrees C. This increase was accentuated in pho1-2 and absent in pho2-1. NADP-glyceraldehyde-3-phosphate dehydrogenase, plastidic fructose-1,6-bisphosphatase and aldolase activity increase relative to phosphoglycerate kinase, transketolase and phosphoribulokinase in wild-type leaves at 5 degrees C. This shift was accentuated in pho1-2 and reversed in pho2-1. Transcript levels for COR genes increase transiently 1 day after transfer to 5 degrees C but were very low in leaves that developed at 5 degrees C in wild-type Arabidopsis, pho1-2 and pho2-1. We conclude that low phosphate plays an important role in triggering cold acclimatization of leaves, leading in particular to an increase of Rubisco expression, changes in other Calvin cycle enzymes to minimize sequestration of phosphate in metabolites, and increased expression of sucrose biosynthesis enzymes.
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PMID:The role of inorganic phosphate in the development of freezing tolerance and the acclimatization of photosynthesis to low temperature is revealed by the pho mutants of Arabidopsis thaliana. 1106 11

In metabolic pathway analysis, it should be considered that many enzymes operate with low specificity (e.g. nucleoside diphosphokinase, uridine kinase, transketolase, aldolase), so that various substrates and products can be converted. Here, we analyze the effect of enzymes with low substrate specificity on the elementary flux modes (pathways). We also study the benefits of two different approaches to describing multifunctional enzymes. The usual description is in terms of (overall) enzymatic reactions. At a more detailed level, the reaction steps (half-reactions, hemi-reactions) of the formation and conversion of enzyme-substrate complexes are considered. Multifunctional enzymes operate according to various mechanisms. This is illustrated here by the reaction schemes for the different enzyme mechanisms of bifunctional enzymes. For enzymes with two or more functions, it is important to consider only linearly independent functions, because otherwise cyclic elementary modes would occur which do not perform any net transformation. However, the choice of linearly independent functions is not a priori unique. We give a method for making this choice unique by considering the extreme pathways of the hemi-reactions system. A formal application of the algorithm for computing elementary flux modes (pathways) yields the result that the number of such modes sometimes depend on the level of description if some reactions are reversible and the products of the multifunctional enzymes are external metabolites or some multifunctional enzymes partly share the same metabolites. However, this problem can be solved by appropriate interpretation of the definition of elementary modes and the correct choice of independent functions of multifunctional enzymes. The analysis is illustrated by a biochemical example taken from nucleotide metabolism, comparing the two ways of description for nucleoside diphosphokinase and adenylate kinase, and by several smaller examples.
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PMID:Treatment of multifunctional enzymes in metabolic pathway analysis. 1222 40

At present two alternative methods are available for analyzing the fluxes in a metabolic network: (1) combining measurements of net conversion rates with a set of metabolite balances including the cofactor balances, or (2) leaving out the cofactor balances and fitting the resulting free fluxes to measured (13)C-labeling data. In this study these two approaches are applied to the fluxes in the glycolysis and pentose phosphate pathway of Penicillium chrysogenum growing on either ammonia or nitrate as the nitrogen source, which is expected to give different pentose phosphate pathway fluxes. The presented flux analyses are based on extensive sets of 2D [(13)C, (1)H] COSY data. A new concept is applied for simulation of this type of (13)C-labeling data: cumulative bondomer modeling. The outcomes of the (13)C-labeling based flux analysis substantially differ from those of the pure metabolite balancing approach. The fluxes that are determined using (13)C-labeling data are shown to be highly dependent on the chosen metabolic network. Extending the traditional nonoxidative pentose phosphate pathway with additional transketolase and transaldolase reactions, extending the glycolysis with a fructose 6-phosphate aldolase/dihydroxyacetone kinase reaction sequence or adding a phosphoenolpyruvate carboxykinase reaction to the model considerably improves the fit of the measured and the simulated NMR data. The results obtained using the extended version of the nonoxidative pentose phosphate pathway model show that the transketolase and transaldolase reactions need not be assumed reversible to get a good fit of the (13)C-labeling data. Strict statistical testing of the outcomes of (13)C-labeling based flux analysis using realistic measurement errors is demonstrated to be of prime importance for verifying the assumed metabolic model.
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PMID:Metabolic flux and metabolic network analysis of Penicillium chrysogenum using 2D [13C, 1H] COSY NMR measurements and cumulative bondomer simulation. 1274 Sep 35

Meloche, H. P., Jr. (Northern Regional Research Laboratory, Peoria, Ill.). Enzymatic utilization of glucose by a basidiomycete. J. Bacteriol. 83:766-774. 1962.-Cell-free extracts of acetone-dried Lactarius torminosus NRRL 2900 were prepared. These extracts contained hexokinase. They also contained triphosphopyridine nucleotide (TPN)-specific glucose-6-phosphate dehydrogenase and catalyzed the reduction of TPN in the presence of d-fructose-6-phosphate, 6-phospho-d-gluconic acid (6PG), and d-ribose-5-phosphate (R5P). Aged preparations oxidized d-glucose-6-phosphate (G6P) to 6PG, whereas fresh preparations oxidized G6P to a pentose with the uptake of 1 mumole of O(2) and the evolution of 1 mumole of CO(2) per mumole of G6P. Evidence for the action of transketolase in the metabolism of R5P by cell-free extracts was obtained.Cell-free preparations lacked hexosediphosphate enzymes. Triosephosphate isomerase and F6P kinase could not be demonstrated; however, aldolase activity was present. Evidence is presented for the conversion of d-glyceraldehyde-3-phosphate to pyruvate. In addition, phosphohexoisomerase was demonstrated. It appears that a hexosemonophosphate pathway operates in L. torminosus extracts and may be the major mechanism of glucose dissimilation in this organism.
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PMID:Enzymatic utilization of glucose by a basidiomycete. 1447 42

Bacillus methanolicus can efficiently utilize methanol as a sole carbon source and has an optimum growth temperature of 50 degrees C. With the exception of mannitol, no sugars have been reported to support rapid growth of this organism, which is classified as a restrictive methylotroph. Here we describe the DNA sequence and characterization of a 19,167-bp circular plasmid, designated pBM19, isolated from B. methanolicus MGA3. Sequence analysis of pBM19 demonstrated the presence of the methanol dehydrogenase gene, mdh, which is crucial for methanol consumption in this bacterium. In addition, five genes (pfk, encoding phosphofructokinase; rpe, encoding ribulose-5-phosphate 3-epimerase; tkt, encoding transketolase; glpX, encoding fructose-1,6-bisphosphatase; and fba, encoding fructose-1,6-bisphosphate aldolase) with deduced roles in methanol assimilation via the ribulose monophosphate pathway are encoded by pBM19. A shuttle vector, pTB1.9, harboring the pBM19 minimal replicon (repB and ori) was constructed and used to transform MGA3. Analysis of the resulting recombinant strain demonstrated that it was cured of pBM19 and was not able to grow on methanol. A pTB1.9 derivative harboring the complete mdh gene could not restore growth on methanol when it was introduced into the pBM19-cured strain, suggesting that additional pBM19 genes are required for consumption of this carbon source. Screening of 13 thermotolerant B. methanolicus wild-type strains showed that they all harbor plasmids similar to pBM19, and this is the first report describing plasmid-linked methylotrophy in any microorganism. Our findings should have an effect on future genetic manipulations of this organism, and they contribute to a new understanding of the biology of methylotrophs.
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PMID:Plasmid-dependent methylotrophy in thermotolerant Bacillus methanolicus. 1497 41

A low virulent Candida albicans mutant, CNC13, deleted in the Mitogen Activated Protein (MAP) kynase HOG1 was used to immunize BALB/c mice. Hog1p is essential for the oxidative stress and hyperosmolarity responses. Several doses and immunization procedures were employed. The protection capacity of the different sera generated was analyzed in a murine model of systemic candidiasis. Using a proteomic approach (two-dimensional gel electrophoresis followed by Western blotting), we were able to distinguish two categories of serum: protective and nonprotective, which showed different titres of total Immunoglobulins (Igs) and IgG2a (analyzed by enzyme-linked immunosorbent assay). The levels of Igs and IgG2a in protective sera were significantly higher compared to nonprotective sera. The pattern of a "nonprotective" profile was composed of enolase (Eno1p), transketolase, heat shock protein and methionine synthase. Only antibodies against enolase are the IgG2a isotype. The pattern of a "protective" sera, on the other hand, was composed of antibodies against the following antigens: several isoforms of Eno1p, pyruvate decarboxylase, pyruvate kynase, a protein of the 40S ribosomal subunit, triosephosphate isomerase, DL-glycerol phosphatase and fructose-bisphosphate aldolase. All these antibodies are the IgG2a isotype. The proteins described in the protective sera might be useful for future vaccine development.
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PMID:Contribution of the antibodies response induced by a low virulent Candida albicans strain in protection against systemic candidiasis. 1504

A novel scheme employing enzymatic catalysts is described enabling conversion of D-ribulose-1,5-bisphosphate (RuBP) from 3-phospho-D-glycerate (3-PGA) without loss of carbon. Bioreactors harboring immobilized enzymes namely, phosphoglycerate kinase (PGK), glycerate phosphate dehydrogenase, triose phosphate isomerase (TIM), aldolase, transketolase (TKL), phosphatase (PTASE/FP), epimerase (EMR) and phosphoribulokinase (PRK), in accordance with this novel scheme were employed. These reactors were designed and constructed based on simulations carried out to study their performance under various operational conditions and allowed production of about 56 +/- 3% RuBP from 3-PGA. This method of synthesis of RuBP from 3-PGA employing immobilized enzyme bioreactors may be used for continuous regeneration of RuBP in biocatalytic carbon dioxide fixation processes from emissions where RuBP acts as acceptor of carbon dioxide to produce 3-PGA, rendering the fixation process continuous.
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PMID:Cascade of bioreactors in series for conversion of 3-phospho-D-glycerate into D-ribulose-1,5-bisphosphate: kinetic parameters of enzymes and operation variables. 1521 6

Malignant gliomas (astrocytomas) are lethal tumors that invade the brain. Invasive cell migration is initiated by extension of pseudopodia into interstitial spaces. In this study, U87 glioma cells formed pseudopodia in vitro as cells pushed through 3 microm pores of polycarbonate membranes. Harvesting pseudopodia in a novel two-step method provided material for proteomic analysis. Differences in the protein profiles of pseudopodia and whole cells were found using differential gel electrophoresis (DIGE) and immunoblotting. Proteins from two-dimensional (2D) gels with M(R)'s of 20-100 kDa and pI's of 3.0-10.0 were identified by peptide mass fingerprinting analysis using mass spectrometry. For DIGE, lysates of pseudopodia and whole cells were each labeled with electrophilic forms of fluorescent dyes, Cy3 or Cy5, and analyzed as mixtures. Analysis was repeated with reciprocal labeling. Differences in protein distributions were detected by manual inspection and computer analysis. Topographical digital maps of the scanned gels were used for algorithmic spot matching, normalization of background, quantifying spot differences, and elimination of artifacts. Pseudopodial proteins in Coomassie-stained 2D gels included isoforms of glycolytic enzymes as the largest group, seven of 24 proteins. Peptide mass fingerprint analysis of DIGE gels demonstrated increased isoforms of annexin (Anx) I, AnxII, enolase, pyruvate kinase, and aldolase, and decreased mitochondrial manganese superoxide dismutase and transketolase in pseudopodia. Specific antibodies showed restricted immunoreactivity of the hepatocyte growth factor (HGF) alpha chain to pseudopodia, indicating localization of its active form. Met (the HGF receptor), actin, and total AnxI were increased in pseudopodial lysates on immunoblots. Increased constituents of the pseudopodial proteome in glioma cells, identified in this study as actin, HGF, Met, and isoforms of AnxI, AnxII, and several glycolytic enzymes, represent therapeutic targets to consider for suppression of tumor invasion.
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PMID:Proteomic characterization of harvested pseudopodia with differential gel electrophoresis and specific antibodies. 1565 57

The sequence of reactions in the Calvin cycle, and the biochemical characteristics of the enzymes involved, have been known for some time. However, the extent to which any individual enzyme controls the rate of carbon fixation has been a long standing question. Over the last 10 years, antisense transgenic plants have been used as tools to address this and have revealed some unexpected findings about the Calvin cycle. It was shown that under a range of environmental conditions, the level of Rubisco protein had little impact on the control of carbon fixation. In addition, three of the four thioredoxin regulated enzymes, FBPase, PRKase and GAPDH, had negligible control of the cycle. Unexpectedly, non-regulated enzymes catalysing reversible reactions, aldolase and transketolase, both exerted significant control over carbon flux. Furthermore, under a range of growth conditions SBPase was shown to have a significant level of control over the Calvin cycle. These data led to the hypothesis that increasing the amounts of these enzymes may lead to an increase in photosynthetic carbon assimilation. Remarkably, photosynthetic capacity and growth were increased in tobacco plants expressing a bifunctional SBPase/FBPase enzyme. Future work is discussed which will further our understanding of this complex and important pathway, particularly in relation to the mechanisms that regulate and co-ordinate enzyme activity.
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PMID:The Calvin cycle revisited. 1624 89


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