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:4.1.1.32 (phosphoenolpyruvate carboxykinase)
4,204 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During embryonic development of the chick, the onset of calcium transport by the chorioallantoic membrane (CAM) is concomitant with the appearance of a calcium-binding protein (CaBP). The development-specific expression of the CaBP in the CAM is inhibited by vitamin K antagonism in ovo with the anticoagulant, warfarin. However, the CaBP remains immunologically detectable in the CAM of warfarin-treated embryos, suggesting the presence of a precursor form of the CaBP. Previously, we have demonstrated that CaBP expression in CAM organ cultures is inducible by vitamin K. Furthermore, the CaBP contains several residues of the modified amino acid, gamma-carboxyglutamic acid (gamma-CGlu), which has been shown to be formed by vitamin K-dependent carboxylation of glutamic acid in several plasma clotting proteins. This study reports the presence of a post-translational, vitamin K-dependent gamma-glutamyl carboxylase activity in the CAM. Our results show that explants of CAM incorporate H14CO3 in an age-specific and vitamin K-dependent manner. Incorporation of H14CO3 by the CAM is further potentiated by warfarin treatment of the embryos, presumably owing to an elevation of the amount of endogenous uncarboxylated protein precursor(s). Among the subcellular (nuclear, mitochondrial, microsomal, and soluble) fractions of the CAM, only microsomes exhibit specific incorporation of of H14CO3 into gamma-CGlu. The CAM microsomal carboxylation activity is post-translational, vitamin K-dependent, specific for prenylated homologs of vitamin K, sensitive to warfarin, and appears to be unrelated to the activities of biotin-dependent carboxylases or phosphoenolpyruvate carboxykinase. Optimal carboxylation activity occurs after incubation of the microsomes with H14CO3 for 60 min at 37 degrees C in the presence of over 100 microgram of vitamin K1/ml.
...
PMID:Vitamin K-dependent gamma-glutamyl carboxylase activity in the chick embryonic chorioallantoic membrane. 10 6

Metabolic responses associated with prolonged fasting and subsequent refeeding of pigs were investigated. Fasting for 14 or 28 days produced significant increases in serum levels of alanine, aspartic and glutamic acid in the three branched-chain amino acids. Glycine, serine and lysine levels were elevated after 28 days of fasting while the levels of histidine, methionine, threonine and phenylalanine were reduced. Fasting markedly stimulated hepatic and renal gluconeogenesis and the activity of the urea cycle enzymes. Fatty acid synthesis and glucose oxidation were virtually abolished in hepatic and adipose tissue in pigs subjected to a 14- or 28-day fast. After the first day of refeeding, the levels of amino acids returned to the control values. The activity of the hepatic urea cycle enzymes, fructose-1,6-diphosphatase and phosphoenolpyruvate carboxykinase remained elevated after the first day of refeeding but returned to the control levels thereafter. The activity of hepatic glucose-6-phosphate dehydrogenase, malic dehydrogenase and acetyl CoA carboxylase were slightly enhanced in pigs refed for 4 and 8 days. The activity of these enzymes in adipose tissue was enhanced 8 days after refeeding. Hepatic synthesis of fatty acids from glucose was slightly stimulated in refed pigs on days 4 and 8 but returned to control values on day 16. Refeeding did not enhance glucose incorporation into fatty acids in adipose tissue above the values observed in fed controls.
...
PMID:Metabolic responses to prolonged fasting and subsequent refeeding in the pig. 55 35

The metabolic consequences of two defects in pyruvate metabolism of the hyphal fungus Aspergillus nidulans have been investigated by natural abundance 13C-NMR spectroscopy. A pyruvate dehydrogenase complex (pdh) mutant, grown on acetate, accumulates alanine upon starvation which is derived from mannitol reserves. The L-alanine level increases further upon incubation with the non-permissive substrate D-glucose. L-Glutamate is absent from these spectra as it is required both for the transamination of pyruvate and as a reaction on an impaired energy metabolism in such a pdh-deficient strain. A pyruvate carboxylase (pyc) mutant, grown upon acetate, only starts to accumulate alanine after a long incubation period with D-glucose, due to the long-lasting presence of phosphoenolpyruvate carboxykinase and malic enzyme, which are both induced by growth on acetate. When this strain is grown on D-fructose and L-glutamate, alanine also accumulates within 3 h upon transfer to D-glucose.
...
PMID:13C-NMR analysis of Aspergillus mutants disturbed in pyruvate metabolism. 331 6

Coryneform bacteria are widely used to produce amino acids, in particularly glutamic acid, by fermentation. To study the metabolic fate of glucose as the carbon source, we developed a method to analyze intracellular extracts by NMR and HPLC. The intracellular metabolites represent the metabolic state of the cells. Glutamic acid was the major metabolic intermediate found in the extracts and its 13C isotopic enrichment reflected that of pyruvic acid. Thus, it was possible to determine the respective contributions of the two major glucose catabolic pathways during the exponential growth phase; glycolysis (55%) and the pentose phosphate pathway (45%). Absolute glutamate 13C enrichments resulting from the incorporation of [1-13C]glucose were determined to quantify the contribution of several metabolic pathways such as anaplerotic pathways (61%; phosphoenolpyruvate carboxylase, pyruvate carboxylase, malic enzyme), a single turn (32%) or multiple turns of the Krebs cycle and the glyoxylate shunt, to oxaloacetate synthesis. A previously described model was adapted to C. melassecola for these calculations. The Krebs cycle was active, whereas the glyoxylate shunt was inactive in exponentially growing cells of C. melassecola with glucose as the sole carbon source. The contributions of anaplerotic enzymes and pyruvate dehydrogenase to replenishing the Krebs' cycle were determined to be 38% and 62%, respectively.
...
PMID:13C-NMR studies of Corynebacterium melassecola metabolic pathways. 785 27

The two main contributions of this article are the solidification of Corynebacterium glutamicum biochemistry guided by bioreaction network analysis, and the determination of basal metabolic flux distributions during growth and lysine synthesis. Employed methodology makes use of stoichiometrically based mass balances to determine flux distributions in the C. glutamicum metabolic network. Presented are a brief description of the methodology, a thorough literature review of glutamic acid bacteria biochemistry, and specific results obtained through a combination of fermentation studies and analysis-directed intracellular assays. The latter include the findings of the lack of activity of glyoxylate shunt, and that phosphoenolpyruvate carboxylase (PPC) is the only anaplerotic reaction expressed in C. glutamicum cultivated on glucose minimal media. Network simplifications afforded by the above findings facilitated the determination of metabolic flux distributions under a variety of culture conditions and led to the following conclusions. Both the pentose phosphate pathway and PPC support significant fluxes during growth and lysine overproduction, and that flux partitioning at the glucosa-6-phosphate branch point does not appear to limit lysine synthesis.
...
PMID:Metabolic flux distributions in Corynebacterium glutamicum during growth and lysine overproduction. Reprinted from Biotechnology and Bioengineering, Vol. 41, Pp 633-646 (1993). 1069 64

Cytosolic pyruvate kinase (PKc) from Brassica napus suspension cells was purified 201-fold to electrophoretic homogeneity and a final specific activity of 51 micromol phosphoenolpyruvate utilized per min per mg protein. SDS/PAGE and gel filtration analyses of the final preparation indicated that this PKc is a 220-kDa homotetramer composed of 56-kDa subunits. The enzyme was relatively heat-stable and displayed a broad pH optimum of pH 6.8. PKc activity was absolutely dependent upon the simultaneous presence of a bivalent and univalent cation, with Mg2+ and K+ fulfilling this requirement. Hyperbolic saturation kinetics were observed for phosphoenolpyruvate, ADP, Mg2+ and K+ (apparent Km values = 0.12, 0.075, 0.21 and 0.48 mM, respectively). Although the enzyme utilized UDP, CDP and IDP as alternative nucleotides, ADP was the preferred substrate. L-Glutamate, oxalate, and the flavonoids rutin and quercetin were the most effective inhibitors (I50 values = 4, 0.3, 0.07, and 0.10 mM, respectively). L-Aspartate functioned as an activator (Ka = 0.31 mM) by causing a 40% increase in Vmax while completely reversing the inhibition of PKc by L-glutamate. Reciprocal control by L-aspartate and L-glutamate is specific for these amino acids and provides a rationale for the in vivo activation of PKc that occurs during periods of enhanced NH +4-assimilation. Allosteric features of B. napus PKc are compared with those of B. napus phosphoenolpyruvate carboxylase. A model is presented that highlights the pivotal role of L-aspartate and L-glutamate in the coordinate regulation of these key phosphoenolpyruvate utilizing cytosolic enzymes.
...
PMID:Purification and characterization of cytosolic pyruvate kinase from Brassica napus (rapeseed) suspension cell cultures: implications for the integration of glycolysis with nitrogen assimilation. 1088 Sep 71

Cytosolic pyruvate kinase (PK(c)) from ripened banana (Musa cavendishii L.) fruits has been purified 543-fold to electrophoretic homogeneity and a final specific activity of 59.7 micromol of pyruvate produced/min per mg of protein. SDS/PAGE and gel-filtration FPLC of the final preparation indicated that this enzyme exists as a 240 kDa homotetramer composed of subunits of 57 kDa. Although the enzyme displayed a pH optimum of 6.9, optimal efficiency in substrate utilization [in terms of V(max)/K(m) for phosphoenolpyruvate (PEP) or ADP] was equivalent at pH 6.9 and 7.5. PK(c) activity was absolutely dependent upon the presence of a bivalent and a univalent cation, with Mg(2+) and K(+) respectively fulfilling this requirement. Hyperbolic saturation kinetics were observed for the binding of PEP, ADP, Mg(2+) and K(+) (K(m) values of 0.098, 0.12, 0.27 and 0.91 mM respectively). Although the enzyme utilized UDP, IDP, GDP and CDP as alternative nucleotides, ADP was the preferred substrate. L-Glutamate and MgATP were the most effective inhibitors, whereas L-aspartate functioned as an activator by reversing the inhibition of PK(c) by L-glutamate. The allosteric features of banana PK(c) are compared with those of banana PEP carboxylase [Law and Plaxton (1995) Biochem. J. 307, 807-816]. A model is presented which highlights the roles of cytosolic pH, MgATP, L-glutamate and L-aspartate in the co-ordinate control of the PEP branchpoint in ripening bananas.
...
PMID:Purification and characterization of cytosolic pyruvate kinase from banana fruit. 1110 98

The taproot from sugar beet (Beta vulgaris L.) undergoes a specific developmental process to function as a food storage organ. Suppression Subtractive Hybridization (SSH) was utilized for the isolation of cDNA fragments for taproot expressed genes. Isolation and molecular analysis of six cDNAs encoding the complete gene product revealed that these genes comprise homologues of a drought-inducible linker histone, a homologue of a major latex-like protein, a phosphoenolpyruvate carboxylase kinase, a putative vacuolar processing enzyme, a thaumatin-like protein and an alanine- and glutamic acid-rich protein. All genes are transcribed in taproots while transcription in leaves is low or undetectable.
...
PMID:Isolation and molecular analysis of six taproot expressed genes from sugar beet. 1202 3

Our objective was to understand the influence of dietary gluconeogenic amino acids on hepatic glucose metabolism in rainbow trout (Oncorhynchus mykiss). We analyzed the effects of partial substitution of dietary protein by a single gluconeogenic dispensable amino acid (DAA: alanine, aspartic acid or glutamic acid), on the regulation of hepatic glycolytic and gluconeogenic enzymes. We fed juvenile rainbow trout with isonitrogenous and isoenergetic diets in which part of nitrogen from fishmeal was replaced by nitrogen from one of the three DAA. Fish were fed over 9 weeks and samples withdrawn 6 h after feeding or 5 days after food deprivation. Our data did not show a clear effect of an excess of DAA on activities of glycolytic enzymes (glucokinase and pyruvate kinase) compared to the control diet. In contrast, feeding caused a significant repression of gluconeogenic enzyme activities (glucose-6-phosphatase, fructose-1,6-bisphosphatase and mitochondrial phosphoenolpyruvate carboxykinase) only in fish fed the three DAA substituted diets. However, these differences were insufficient to affect postprandial glycemia significantly. In conclusion, an excess of dietary DAA tested does not seem to modify glycemia or to have a negative impact on dietary carbohydrate utilization in rainbow trout.
...
PMID:Effect of partial substitution of dietary protein by a single gluconeogenic dispensable amino acid on hepatic glucose metabolism in rainbow trout (Oncorhynchus mykiss). 1254 63

Transgenic Medicago truncatula plants were produced harboring chimeric gene constructs of the glutamine synthetase (GS) cDNA clones (MtGS1a or MtGS1b) fused in sense or antisense orientation to the nodule-specific leghemoglobin promoter Mtlb1. A series of transgenic plants were obtained showing a 2- to 4-fold alteration in nodule GS activity when compared with control plants. Western and northern analyses revealed that the increased or decreased levels of GS activity correlate with the amount of cytosolic GS polypeptides and transcripts present in the nodule extracts. An analysis of the isoenzyme composition showed that the increased or decreased levels of GS activity were attributable to major changes in the homo-octameric isoenzyme GS1a. Nodules of plants transformed with antisense GS constructs showed an increase in the levels of both asparagine synthetase (AS) polypeptides and transcripts when compared with untransformed control plants, whereas the sense GS transformants showed decreased AS transcript levels but polypeptide levels similar to control plants. The polypeptide abundance of other nitrogen metabolic enzymes NADH-glutamic acid synthase and aspartic acid amino-transferase as well as those of major carbon metabolic enzymes phosphoenolpyruvate carboxylase, carbonic anhydrase, and sucrose synthase were not affected by the GS-gene manipulations. Increased levels of AS polypeptides and transcripts were also transiently observed in nodules by inhibiting GS activity with phosphinothricin. Taken together, the results presented here suggest that GS activity negatively regulates the level of AS in root nodules of M. truncatula. The potential role of AS in assimilating ammonium when GS becomes limiting is discussed.
...
PMID:Nodule-specific modulation of glutamine synthetase in transgenic Medicago truncatula leads to inverse alterations in asparagine synthetase expression. 1297 Apr 90


1 2 Next >>

---