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

---

Query: EC:4.1.1.49 (phosphoenolpyruvate carboxykinase)
4,654 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method for determining the subcellular metabolite levels in spinach protoplasts is described. The protoplasts are disrupted by centrifugation through a nylon net, releasing intact chloroplasts which pass through a layer of silicone oil into perchloric acid while the remaining cytoplasmic components remain over the oil and are simultaneously quenched as acid is centrifuged into them. Cross-contamination is measured and corrected for using ribulose 1,5-bisphosphate as a chloroplastic marker and phosphoenolpyruvate carboxylase as a cytoplasmic marker. A method for separation of intact protoplasts from the medium by silicone oil centrifugation is described, which allows a correction to be made for the effect of free chloroplasts and broken protoplasts. Methods for inhibiting chloroplast photosynthesis, without inhibiting protoplasts, are presented. It is demonstrated that ribulose 1,5-bisphosphate, ATP, ADP, AMP, inorganic phosphate, hexose phosphate, triose phosphate, fructose 1,6-bisphosphate, and 3-phosphoglycerate can be reliably recovered in the subcellular fractions isolated from protoplasts, and measured by enzymic substrate analysis.
...
PMID:Enzymic determination of metabolites in the subcellular compartments of spinach protoplasts. 1666 85

Autoradiography of total soluble maize (Zea mays) leaf proteins incubated with (32)P-labeled adenylates and separated by denaturing electrophoresis revealed that many polypeptides were phosphorylated in vitro by endogenous protein kinase(s). The most intense band was at 94 to 100 kilodaltons and was observed when using either [gamma-(32)P]ATP or [beta-(32)P]ADP as the phosphate donor. This band was comprised of the subunits of both pyruvate, Pi dikinase (PPDK) and phosphoenolpyruvate carboxylase (PEPCase). PPDK activity was previously shown to be dark/light-regulated via a novel ADP-dependent phosphorylation/Pi-dependent dephosphorylation of a threonyl residue. The identity of the acid-stable 94 to 100 kilodalton band phosphorylated by ATP was established unequivocally as PEPCase by two-dimensional gel electrophoresis and immunoblotting. The phosphorylated amino acid was a serine residue, as determined by two-dimensional thin-layer electrophoresis. While the in vitro phosphorylation of PEPCase from illuminated maize leaves by an endogenous protein kinase resulted in a partial inactivation ( approximately 25%) of the enzyme when assayed at pH 7 and subsaturating levels of PEP, effector modulation by l-malate and glucose-6-phosphate was relatively unaffected. Changes in the aggregation state of maize PEPCase (homotetrameric native structure) were studied by nondenaturing electrophoresis and immunoblotting. Enzyme from leaves of illuminated plants dissociated upon dilution, whereas the protein from darkened tissue did not dissociate, thus indicating a physical difference between the enzyme from light- versus dark-adapted maize plants.
...
PMID:In vitro phosphorylation of maize leaf phosphoenolpyruvate carboxylase. 1666 42

The effects of adenine nucleotides on phosphoenolypyruvate carboxylase were investigated using purified enzyme from the CAM plant, Crassula argentea. At 1 millimolar total concentration and with limiting phosphoenolpyruvate, AMP had a stimulatory effect, lowering the K(m) for phosphoenolpyruvate, ADP caused less stimulation, and ATP decreased the activity by increasing the K(m) for phosphoenolpyruvate. Activation by AMP was not additive to the stimulation by glucose 6-phosphate. Furthermore, AMP increased the K(a) for glucose 6-phosphate. Inhibition by ATP was competitive with phosphoenolpyruvate. In support of the kinetic data, fluorescence binding studies indicated that ATP had a stronger effect than AMP on phosphoenolpyruvate binding, while AMP was more efficient in reducing glucose 6-phosphate binding. As free Mg(2+) was held constant and saturating, these effects cannot be ascribed to Mg(2+) chelation. Accordingly, the enzyme response to the adenylate energy charge was basically of the "R" type (involving enzymes of ATP regenerating sequences) according to D. E. Atkinson's (1968 Biochemistry 7: 4030-4034) concept of energy charge regulation. The effect of energy charge was abolished by 1 millimolar glucose 6-phosphate. Levels of glucose 6-phosphate and of other putative regulatory compounds of phosphoenolpyruvate carboxylase were determined in total leaf extracts during a day-night cycle. The level of glucose 6-phosphate rose at night and dropped sharply during the day. Such a decrease in glucose 6-phosphate concentration could permit an increased control of phosphoenolpyruvate carboxylase by energy charge during the day.
...
PMID:The Effect of Adenine Nucleotides on Purified Phosphoenolpyruvate Carboxylase from the CAM Plant Crassula argentea. 1666 57

The net photosynthetic rate and the activities of ribulose 1,5 bisphosphate carboxylase (RubisCo), phosphoenolpyruvate carboxylase, sucrose-P-synthase, and ADP glucose-pyrophosphorylase, key enzymes of the leaf carbohydrate metabolism were compared in eight maize (Zea mays L.) genotypes presenting large differences in growth rate. The sucrose-P-synthase activity varied in the ratio 1 to 3 from the less active to the more active genotype and this variation was highly correlated with those in growth rate. ADP glucose pyrophosphorylase activity was not significantly different from one genotype to another whatever the basis for expression, leaf area, or soluble protein. The photosynthetic rate varied with similar amplitude (1:1) to the RubisCo activity or RubisCo quantity but the correlation with growth rate was highly significant for photosynthesis and nonsignificant for RubisCo or phosphoenolpyruvate carboxylase. So, in our series of genotypes the sucrose synthesis capacities as expressed by sucrose phosphate synthase activity seem to have a good predicting value for mean growth rate at a young stage.
...
PMID:Genetic Variability in Carbon Fixation, Sucrose-P-Synthase and ADP Glucose Pyrophosphorylase in Maize Plants of Differing Growth Rate. 1666 58

Phosphoenolpyruvate phosphatase from Brassica nigra leaf petiole suspension cells has been purified 1700-fold to apparent homogeneity and a final specific activity of 380 micromole pyruvate produced per minute per milligram protein. Purification steps included: ammonium sulfate fractionation, S-Sepharose, chelating Sepharose, concanavalin A Sepharose, and Superose 12 chromatography. The native protein was monomeric with a molecular mass of 56 kilodaltons as estimated by analytical gel filtration. The enzyme displayed a broad pH optimum of about pH 5.6 and was relatively heat stable. Western blots of microgram quantities of the final preparation showed no cross-reactivity when probed with rabbit polyclonal antibodies prepared against either castor bean endosperm cytosolic pyruvate kinase, or sorghum leaf phosphoenolpyruvate carboxylase. The final preparation exhibited a broad substrate selectivity, showing high activity toward p-nitrophenyl phosphate, adenosine diphosphate, adenosine triphosphate, gluconate 6-phosphate, and phosphoenolpyruvate, and moderate activity toward several other organic phosphates. Phosphoenolpyruvate phosphatase possessed at least a fivefold and sixfold greater affinity and specificity constant, respectively, for phosphoenolpyruvate (apparent Michaelis constant = 50 micromolar) than for any other nonartificial substrate. The enzyme was activated 1.7-fold by 4 millimolar magnesium, but was strongly inhibited by molybdate, fluoride, zinc, copper, iron, and lead ions, as well as by orthophosphate, ascorbate, glutamate, aspartate, and various organic phosphate compounds. It is postulated that phosphoenolpyruvate phosphatase functions to bypass the adenosine diphosphate dependent pyruvate kinase reaction during extended periods of orthophosphate starvation.
...
PMID:Purification and Characterization of a Phosphoenolpyruvate Phosphatase from Brassica nigra Suspension Cells. 1666 36

When Brassica nigra leaf petiole suspension cells were subjected to 7 days of inorganic phosphate (Pi) starvation the extractable activity of: (a) pyrophosphate:fructose 6-phosphate 1-phosphotransferase, nonphosphorylating NADP-glyceraldehyde 3-phosphate dehydrogenase, phosphoenolpyruvate phosphatase, and phosphoenolpyruvate carboxylase increased at least fivefold, (b) phosphorylating NAD-glyceraldehyde 3-phosphate dehydrogenase decreased about sixfold, and (c) ATP:fructose 6-phosphate 1-phosphotransferase, 3-phosphoglycerate kinase, pyruvate kinase, or NAD malic enzyme was not altered. Pi deprivation also resulted in significant reductions in extractable levels of Pi, ATP, ADP, fructose 2,6-bisphosphate, and soluble protein, but caused a sixfold elevation in free amino acid concentrations. No change in inorganic pyrophosphate concentration was observed following Pi starvation. It is hypothesized that pyrophosphate:fructose 6-phosphate 1-phosphotransferase, nonphosphorylating NADP-glyceraldehyde 3-phosphate dehydrogenase, and phosphoenolpyruvate phosphatase bypass nucleotide phosphate or Pi-dependent glycolytic reactions during sustained periods of Pi depletion.
...
PMID:Phosphate Starvation Inducible ;Bypasses' of Adenylate and Phosphate Dependent Glycolytic Enzymes in Brassica nigra Suspension Cells. 1666 22

The effects of phosphorus nutrition on several physiological and biochemical parameters of the green alga, Selenastrum minutum, have been examined. Algal cells were cultured in chemostats under conditions of either Pi limitation or nutrient sufficiency. Pi limitation resulted in: (a) a 5-fold lower rate of respiration, (b) a 3-fold decline in rates of photosynthetic carbon dioxide fixation and oxygen evolution, (c) a 3-fold higher rate of dark carbon dioxide fixation, (d) significant increases in activities of phosphoenolpyruvate (PEP) carboxylase and PEP phosphatase (128% and 158% of nutrient sufficient activities, respectively), (e) significant reductions in activities of nonphosphorylating NADP-glyceraldehyde-3-phosphate dehydrogenase and NAD malic enzyme, and (f) no change in levels of ATP:fructose-6-phosphate 1-phosphotransferase, phosphorylating NAD-glyceraldehyde-3-phosphate dehydrogenase, 3-phosphoglycerate kinase, and pyruvate kinase. The intracellular concentrations of Pi, ATP, AMP, soluble protein, and chlorophyll were also significantly reduced in response to Pi limitation. As well, the level of ADP was about 11-fold lower in the Pi-limited cells as compared to the nutrient sufficient controls. It was predicted that because of this low level of ADP, pyruvate kinase catalyzed conversion of PEP to pyruvate may be restricted in Pi-limited cells. During Pi limitation, PEP carboxylase and PEP phosphatase may function to "bypass" the ADP dependent pyruvate kinase, as well as to recycle Pi for its reassimilation into cellular metabolism.
...
PMID:Effects of Phosphorus Limitation on Respiratory Metabolism in the Green Alga Selenastrum minutum. 1666 95

Saccharomyces cerevisiae phosphoenolpyruvate (PEP) carboxykinase catalyzes the reversible formation of oxaloacetate and adenosine triphosphate from PEP, adenosine diphosphate and carbon dioxide, and uses Mn(2+) as the activating metal ion. Comparison with the crystalline structure of homologous Escherichia coli PEP carboxykinase [Tari et al. (1997) Nature Struct. Biol. 4, 990-994] shows that Lys(213) is one of the ligands to Mn(2+) at the enzyme active site. Coordination of Mn(2+) to a lysyl residue is not common and suggests a low pK (a) value for the epsilon-NH(2) group of Lys(213). In this work, we evaluate the role of neighboring Phe(216) in contributing to provide a low polarity microenvironment suitable to keep the epsilon-NH(2) of Lys(213) in the unprotonated form. Mutation Phe216Tyr shows that the introduction of a hydroxyl group in the lateral chain of the residue produces a substantial loss in the enzyme affinity for Mn(2+), suggesting an increase of the pK (a) of Lys(213). In agreement with this interpretation, theoretical calculations indicate an alkaline shift of 2.8 pH units in the pK (a) of the epsilon-amino group of Lys(213) upon Phe216Tyr mutation.
...
PMID:Relevance of phenylalanine 216 in the affinity of Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase for Mn(II). 1719 42

The kinetic affinity for CO(2) of phosphoenolpyruvate PEP(5) carboxykinase from Anaerobiospirillum succiniciproducens, an obligate anaerobe which PEP carboxykinase catalyzes the carboxylation of PEP in one of the final steps of succinate production from glucose, is compared with that of the PEP carboxykinase from Saccharomyces cerevisiae, which catalyzes the decarboxylation of oxaloacetate in one of the first steps in the biosynthesis of glucose. For the A. succiniciproducens enzyme, at physiological concentrations of Mn(2+) and Mg(2+), the affinity for CO(2) increases as the ATP/ADP ratio is increased in the assay medium, while the opposite effect is seen for the S. cerevisiae enzyme. The results show that a high ATP/ADP ratio favors CO(2) fixation by the PEP carboxykinase from A. succiniciproducens but not for the S. cerevisiae enzyme. These findings are in agreement with the proposed physiological roles of S. cerevisiae and A. succiniciproducens PEP carboxykinases, and expand recent observations performed with the enzyme isolated from Panicum maximum (Chen et al. (2002) Plant Physiology 128: 160-164).
...
PMID:Comparative kinetic effects of Mn (II), Mg (II) and the ATP/ADP ratio on phosphoenolpyruvate carboxykinases from Anaerobiospirillum succiniciproducens and Saccharomyces cerevisiae. 1721 67

The response of Crassostrea gigas to prolonged hypoxia was investigated for the first time by analyzing the metabolic branch point formed by pyruvate kinase (PK) and hosphoenolpyruvate carboxykinase (PEPCK). PK and PEPCK cDNAs were cloned and sequenced. The main functional domains of the PK sequence, such as the binding sites for ADP/ATP and phosphoenolpyruvate (PEP), were identified whereas the PEPCK sequence showed the specific domain to bind PEP in addition to the kinase-1 and kinase-2 motifs to bind guanosine triphosphate (GTP) and Mg(2+), specific for all PEPCKs. A C-terminal extension was detected for the first time in eukaryota PK. Separation of mitochondrial and cytosolic fraction showed that more than 92% of the PEPCK enzyme activity was cytosolic in gills, digestive gland, mantle and muscle. PK and PEPCK mRNAs and enzyme activities have been measured in muscle during prolonged hypoxia for 20 days. Adaptation of PK in hypoxic muscle at transcriptional level occurred lately by decreasing significantly the PK mRNA level at day 20 while PK enzyme activity was inhibited by the high content of alanine. The PEPCK mRNA ratio in hypoxic muscle significantly increased at day 10 simultaneously to the PEPCK enzyme activity. Succinate accumulation observed at day 10 and day 20 confirmed the anaerobic pathway of muscle metabolism in oyster subjected to hypoxia. Regulation of C. gigas PEPCK in muscle occurred at gene transcription level while PK was first regulated at enzyme level with alanine as allosteric inhibitor, and then at molecular level under a fast effect of hypoxia.
...
PMID:Transcriptional regulation of pyruvate kinase and phosphoenolpyruvate carboxykinase in the adductor muscle of the oyster Crassostrea gigas during prolonged hypoxia. 1748 28


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---