Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.1.1.32 (phosphoenolpyruvate carboxykinase)
4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphoenolpyruvate carboxylase (orthophosphate:oxaloacetate carboxylase (phosphorylating), EC 4.1.1.31) from plant cells of soybean nodules was studied to assess its role in providing carbon skeletons for aspartate and asparagine synthesis. The enzyme was purified 119-fold by (NH4)2SO4 fractionation and DEAE-cellulose, BioGel A-1.5m, and hydroxyapatite chromatography. Five activity bands were resolved with discontinuous polyacrylamide gel electrophoresis. A small quantity of enzyme from the most active band was separated from the others by preparative electrophoresis. The apparent Michaelis constants of this enzyme for phosphoenolpyruvate and HCO3- were 9.4.10(-2) and 4.1.10(-1) mM, respectively. A series of metabolite tested at 1 mM had no significant effect on enzyme activity. These experiments indicate that the major factors directly controlling phosphoenolpyruvate carboxylase activity in vivo are phosphoenolpypyruvate and HCO3- concentrations.
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PMID:Phosphoenolpyruvate carboxylase from soybean nodule cytosol. Evidence for isoenzymes and kinetics of the most active component. 57 39

The activity of phosphoenolpyruvate carboxylase (orthophosphate: oxalacetate-carboxy-lyase phosphorylating, E. C. 4.1.1.31) in the cell extracts of the carboxydobacterium Pseudomonas gazotropha Z-1156 depends on the presence of bivalent metal ions, Mn2+ ions being more effective than Mg2+ ions. The value of apparent KM for phosphoenolpyruvate in a freshly prepared extract is 7.1 mM. The affinity of the enzyme to phosphoenolpyruvate increases after storage of the extract in ice in the presence of dithiothreitol: KM=0.42 mM at low concentrations of the substrate, and 2.5 mm, at high concentrations of the substrate. The calculated maximum rate is 18.1 mE per 1 mg of protein of the extract, and changes only slightly upon storage in the presence of a stabilizer of sulphydryl groups. The activity of the enzyme reaches its maximum at the phase of deceleration of growth. Nucleotide triphosphates inhibit the activity of the enzyme more than the corresponding nucleotide diphosphates. The properties of PEP-carboxylase are discussed from the viewpoint of comparative biochemistry.
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PMID:[Phosphoenolpyruvate carboxylase in the carboyxdobacterium, Pseudomonas gazotropha]. 65 81

Conformational change of phosphoenolpyruvate carboxylase (orthophosphate: oxaloacetate carboxy-lyase (phosphorylating), EC 4.1.1.31) induced by allosteric effectors was investigated using a hydrophobic probe, 1-anilinonaphthalene-8-sulfonate (ANS). Kinetic experiments suggested that ANS binds with the enzyme at the sites which are not involved in the catalytic and regulatory functions, though it partially inhibits the enzyme activity with half-saturation concentration (S0.5) of 38.5 muM. Binding experiments showed that a maximum of 2 mol of ANS are able to bind with 1 mol of the enzyme subunit presumably with an equal dissociation constant to each other (34.5 muM). Flourescence emission of ANS was markedly increased by binding with the enzyme. L-Aspartate, the allosteric inhibitor, and CoASAc and fructose 1,6-bisphosphate (Fru-1,6-P2) the allosteric activators, produced various degrees of change in fluorescence, when added singly or in combinations. The changes were shown to be attributable to the allosteric interactions between the enzyme and effectors from some criteria such as structural specificity, half-saturation concentrations, and heterotropic-homotropic interactions of the ligands. It was concluded from these analyses that the enzyme can be in at least four conformational states which are distinct from each other. Especially noteworthy is the finding that the enzyme, upon simultaneous binding of CoASAc and Fru-1,6-P2, takes a new conformation which is enterely different from those induced by sole binding of each effector. In addition, the heterotropic interaction between the activator and the inhibitor was observed through conformational change by the ANS method, as observed in the kinetic studies.
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PMID:Phosphoenolpyruvate carboxylase of Escherichia coli. Studies on multiple conformational states elicited by allosteric effectors with a fluorescent probe, 1-anilinonaphthalene-8-sulfonate. 79 65

Kinetic studies were done to obtain a quantitative estimation of the synergistic interactions that occur between phosphoenolpyruvate carboxylase (orthophosphate:oxaloacetate carboxylase (phosphorylating) E.C. 4.1.1.31) from Escherichia coli K12 and various combinations of its primary substrate, P-enolpyruvate, and the activators acetylcoenzyme A, CDP, GTP, and fructose 1,6-bisphosphate. The analysis involves the evaluation of apparent K values, KS for P-enolpyru;ate and KA for activators, as a function of the concentration of P-enolpyruvate or another activator in the case of KA determinations. Methods are presented which allow the determination of dissociation constants for P-enolpyruvate and activators from binary, ternary, and quaternary complexes of enzyme with substrates or activators, or both. It was observed that synergistic activation occurs with acetyl coenzyme A and all of the coactivators but not with fructose 1,6-bisphosphate and the other co-activators. The enhancement of binding from the binary enzyme substrate (or activator) complex to the ternary or quaternary complexes is in the range of 100-fold. The dissociation constants for P-enolpyruvate, acetyl coenzyme A, CDP, and fructose 1,6-bisphosphate are the same from any active enzyme species. Synergistic activation by multiple activators reflects the ability of co-activators to shift the equilibrium concentrations of active enzyme species away from the inactive forms via a modified "cascade" scheme, thus decreasing the probability that dissociation of any one activator will yield an inactive enzyme species.
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PMID:Escherichia coli phosphoenolpyruvate carboxylase. Studies on the mechanism of synergistic activation by nucleotides. 698 77

Oral vanadate administration has been demonstrated to normalize blood glucose levels in ob/ob and db/db mice and streptozotocin (STZ) diabetic rats. The exact mechanism of this vanadate effect is uncertain, since there are no consistent effects on the insulin receptor tyrosine kinase activity or phosphotyrosine phosphatase activity. We have therefore studied the postreceptor actions of vanadate, focusing our attention on the steady-state levels of mRNA of enzymes involved in carbohydrate metabolism. When compared with their lean (ob/+) controls, the livers of ob/ob mice exhibited an approximately 90% reduction in the levels of phosphoenolpyruvate carboxykinase (PEPCK) mRNA and twofold to fivefold higher levels of the mRNAs for glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the "liver beta-cell" glucose transporter (GLUT2), and the proto-oncogene c-myc. Administration of sodium vanadate (0.25 mg/mL) in the drinking water of ob/ob mice over a 45-day period resulted in a near normalization of blood glucose and increased PEPCK mRNA levels more than ninefold. Starvation of the ob/ob mice for 24 to 48 hours also increased PEPCK mRNA levels by fourfold to 15-fold. Vanadate treatment did not alter mRNA levels of any other proteins studied and had no effect on PEPCK mRNA in ob/+ mice. However, 1 to 100 mumol/L vanadate produced a concentration-dependent increase in PEPCK mRNA levels in an H35 hepatoma cell line, an effect opposite to the suppression of PEPCK mRNA produced by insulin. In summary, hyperglycemia in the ob/ob mouse is characterized by decreased expression of PEPCK and increased expression of GAPDH mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Vanadate normalizes hyperglycemia and phosphoenolpyruvate carboxykinase mRNA levels in ob/ob mice. 796 88

The consequence of low maternal dietary glucose on perinatal phosphoenolpyruvate carboxykinase (PEPCK EC 4.1.32) gene expression was investigated. Pregnant rats were fed isoenergetic diets containing graded levels of glucose (0, 12, 24, and 60%) from gestation day 2 to lactation day 15. The postnatal developmental profile of PEPCK mRNA in the neonatal kidney was analysed by Northern blot and presented as PEPCK/GAPDH mRNA ratios. In comparison with the 24 and 60% dietary groups, maternal dietary glucose restriction (0 or 12%) during pregnancy resulted in a significant delay in postnatal renal PEPCK gene expression. In these glucose restricted pups, renal PEPCK mRNA was barely detected at birth and was fully visualized only at 4-6 hr; it peaked 24 hr after birth, which was 12 hr later than pups born to dams fed 24 or 60% glucose diets. These results demonstrate for the first time that maternal dietary glucose can modify postnatal renal PEPCK gene expression during perinatal development when glucose homeostasis via gluconeogenesis is critical for neonatal survival.
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PMID:Maternal dietary glucose modifies phosphoenolpyruvate carboxykinase (PEPCK) gene expression in the kidney of newborn rats. 907 Feb 46

Sucrose synthase (SS; EC 2.4.1.13) was radiolabeled in situ by incubating detached soybean nodules with 32Pi. Phosphoamino acid analysis indicated that SS was phosphorylated on a serine residue(s). In-vitro phosphorylation of purified nodule SS by desalted nodule extracts was Ca2+-dependent. This SS-kinase was partially purified (approximately 2200-fold) from nodules harvested from illuminated plants. The molecular mass of the SS-kinase was about 55,000 on a Superdex 75 size-exclusion column or in a denaturing autophosphorylation gel. With either purified nodule SS or Syntide 2 as substrate, exogenous calmodulin and phosphatidylserine showed little or no effect on the in-vitro activity of this partially purified protein kinase. However, its activity was inhibited by W-7. The purified nodule SS-kinase (or CDPK) phosphorylated nodule PEP carboxylase (PEPC; EC 4.1.1.31) in the presence of Ca2+. In contrast, a partially purified nodule PEPC-kinase preparation was incapable of phosphorylating nodule SS. Unlike nodule PEPC [Zhang et al. (1995) Plant Physiol. 108, 1561-1568], the phosphorylation state of SS is not likely modulated in planta by photosynthate supply from the shoots.
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PMID:Seryl-phosphorylation of soybean nodule sucrose synthase (nodulin-100) by a Ca2+-dependent protein kinase. 923 14

Maize leaf phosphoenolpyruvate carboxylase [PEPC; orthophosphate:oxaloacetate carboxy-lyase (phosphorylating), EC 4.1.1.31] protein-serine kinase (PEPC-PK) phosphorylates serine-15 of its target enzyme, thus leading to an increase in catalytic activity and a concomitant decrease in malate sensitivity of this cytoplasmic C4 photosynthesis enzyme in the light. We have recently demonstrated that the PEPC-PK activity in maize leaves is slowly, but strikingly, increased in the light and decreased in darkness. In this report, we provide evidence that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of C4 monocots (maize, sorghum) and dicots (Portulaca oleracea) in the dark or light, completely prevents the in vivo light activation of PEPC-PK activity regardless of whether the protein kinase activity is assessed in vivo or in vitro. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplasts, has no effect on the light activation of maize PEPC-PK. Similarly, treatment with cycloheximide did not influence the light activation of other photosynthesis-related enzymes in maize, including cytoplasmic sucrose-phosphate synthase and chloroplast stromal NADPH-malate dehydrogenase and pyruvate, Pi dikinase. These and related results, in which detached maize leaves were treated simultaneously with cycloheximide and microcystin-LR, a potent in vivo and in vitro inhibitor of the PEPC type 2A protein phosphatase, indicate that short-term protein turnover of the PEPC-PK itself or some other essential component(s) (e.g., a putative protein that modifies this kinase activity) is one of the primary levels in the complex and unique regulatory cascade effecting the reversible light activation/seryl phosphorylation of PEPC in the mesophyll cytoplasm of C4 plants.
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PMID:Protein turnover as a component in the light/dark regulation of phosphoenolpyruvate carboxylase protein-serine kinase activity in C4 plants. 1160 71

Udotea flabellum is a marine, macroscopic green alga with C4-like photosynthetic characteristics, including little O2 inhibition of photosynthesis, a low CO2 compensation point, and minimal photorespiration; but it lacks anatomical features analogous to the Kranz compartmentation of C4 plants, and phosphoenolpyruvate carboxylase [PEPC; orthophosphate:oxaloacetate carboxy-lyase (phosphorylating), EC 4.1.1.31] activity is negligible. Phosphoenolpyruvate carboxykinase (PEPCK) activity (carboxylating) in Udotea extracts was equivalent to that of ribulose-bisphosphate carboxylase [Rubisco; 3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39]. When PEPCK activity was inhibited in vivo with 3-mercaptopicolinic acid (MPA), thallus photosynthesis decreased by 70% and became sensitive to O2. Codium decorticatum, a related species that lacks C4-like photosynthetic features and PEPCK activity, showed no increase in O2 inhibition upon exposure to MPA. Rubisco and PEPC activities in Udotea were not inhibited by MPA. Labeling of the early photosynthetic products malate and aspartate was reduced 66% by MPA, while intermediates of the photorespiratory carbon oxidation cycle showed a 3-fold increase. Udotea evolved O2 in the light in the absence of inorganic carbon, suggesting it had an endogenous carbon source for photosynthesis. Exogenous malate stimulated this process, while MPA inhibited it. PEPCK was not involved in Crassulacean acid metabolism or dark CO2 fixation. These MPA studies establish a direct link between PEPCK activity and the low O2 inhibition of photosynthesis and low photorespiration in Udotea. The data are consistent with carboxylation by a cytosolic PEPCK providing a C4 acid, such as malate, to the chloroplast for decarboxylation to elevate the CO2 concentration at the Rubisco fixation site. Udotea is to date the most primitive plant with a C4-like form of photosynthesis.
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PMID:The role of phosphoenolpyruvate carboxykinase in a marine macroalga with C4-like photosynthetic characteristics. 1160 73

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.
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PMID:Phosphate Starvation Inducible ;Bypasses' of Adenylate and Phosphate Dependent Glycolytic Enzymes in Brassica nigra Suspension Cells. 1666 22


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