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)

1. Rat liver mitochondria oxidizing malate produce PEP (phosphoenolpyruvate) without the addition of ATP or other nucleotides. 2. The addition of oligomycin in the presence of 2,4-dinitrophenol did not abolish PEP formation and in some instances stimulated its formation. 3. Formation of PEP was inhibited by arsenate. 4. Arsenite decreased PEP formation and caused accumulation of pyruvate. 5. Added GTP and ITP had no effect on PEP formation. 6. PEP formed from malate in the presence of GTP and labelled P(i) had a specific radioactivity approximately the same as the P(i) with no contribution from the phosphate of the added GTP. 7. There was no parallelism between the effects of inhibitors on PEP formation from malate and their effects on the assayed activity of PEP carboxykinase. 8. In a direct comparison it was shown that the PEP carboxykinase content of mitochondria was insufficient to account for the PEP formation from malate. 9. Consideration of the kinetic characteristics of PEP carboxykinase and mitochondrial content of oxaloacetate and GTP show that this enzyme cannot account for the PEP formed from malate by mitochondria.
...
PMID:The effect of inhibitors on the formation of phosphoenolpyruvate by rat liver mitochondria. 418 46

A crude preparation of PEP carboxylase (EC 4.1.1.31) from the yellow lupin roots exhibits the pH optimum of activity within the range of 7.4-8.6 and the temperature optimum at 32 - 40 degrees C. Its Km for PEP is 0.1 mM, and Km for HCO3- is 0.7 mM. The affinity of the enzyme towards Mg2+ diminishes with the metal ion concentration. At the concentration of Mg2+ below 0.5 mM Km for Mg2+ is 0.07 mM and at the Mg2+ concentration over 1.5 mM it rises to 0.47 mM. The Hill coefficients are 0.37 and 0.88, respectively. Among several compounds affecting the PEP carboxylase activity, such as organic acids, amino acids, and sugar phosphates, at physiological pH (7.0 and 7.8), malate shows the strongest inhibition of a competitive character, its Ki being 2 mM. Also acidic amino acids strongly inhibit the enzyme activity, aspartate being more effective than glutamate. Glucose 6-phosphate and fructose 1,6-diphosphate markedly activate the enzyme. Both the inhibition by malate, aspartate and glutamate, and the activation by sugar phosphates rises considerably when pH is decreased from 7.8 to 7.0. Malonate scarcely affects the enzyme.
...
PMID:Phosphoenolpyruvate carboxylase from the roots of yellow lupin (Lupinus luteus). 667 22

3-Mercaptopicolinate (3-MPA) is a specific inhibitor of phosphoenolpyruvate carboxykinase (PEP CK). In vivo the hypoglycaemic action of 3-MPA in 24 h-starved rats was abolished on intragastric glucose refeeding. Nonetheless, 3-MPA decreased hepatic glycogen content and rate of synthesis in starved animals re-fed glucose. The inference is that on re-feeding after starvation hepatic glycogen is synthesised mainly de novo via glyconeogenesis involving PEP CK. 3-MPA increased hepatic lipogenesis in water- and glucose-fed normal and diabetic rats. This increase is presumed to result from inhibition of PEP CK and consequent diversion of pyruvate from gluconeogenesis to lipogenesis. In contrast, 3-MPA inhibited brown-fat lipogenesis in water- and glucose-fed rats.
...
PMID:Direction of carbon flux in starvation and after refeeding: in vitro and in vivo effects of 3-mercaptopicolinate. 667 46

Microfilariae of bovine filarial parasite Setaria cervi are equipped with the enzymes of glycolysis, pentose phosphate and PEP-succinate pathways and thus resemble the adult form in its metabolic pattern. Malate dehydrogenase was the most active enzyme in microfilariae followed by lactic dehydrogenase and fumarase, while phosphoglucoisomerase, PEP-carboxykinase and FDP-aldolase were comparatively less active. The very low ratio of PK/PEPCK in S. cervi microfilariae indicates active fixation of CO2 into PEP to produce oxalacetate. Centperazine and diethylcarbamazine significantly inhibited PEP-carboxykinase, fumarate reductase and succinic dehydrogenase, suggesting that these antifilarials probably exert microfilaricidal action by blocking the PEP-succinate pathway.
...
PMID:Setaria cervi: enzymes in microfilariae and in vitro action of antifilarials. 715 43

Evidence is presented in support of a pathway in skeletal muscle of glyconeogenesis (glycogen biosynthesis de novo) from L-glutamate and related amino acids involving the enzyme phosphoenolpyruvate carboxykinase (PEP CK). In the rat hemidiaphragm in vitro, not only did L-[U]-14C]glutamate exert a glycogen-sparing action, but 14C-label was incorporated into glycogen. The incorporation is thought not to be simply via label randomization and was decreased by factors that increased glycolysis or pyruvate oxidation. 3-Mercaptopicolinate and amino-oxyacetate, specific inhibitors of PEP CK and aminotransferase-type enzymes, respectively, decreased 14C-incorporation from L-[U-14C]glutamate into glycogen. No quantitative determination of apparent glyconeogenic flux was made, and it remains to be established whether glyconeogenesis via PEP CK and/or via PEP CK coupled with "malic' enzyme (or pyruvate carboxylase) is functionally important in skeletal muscle.
...
PMID:A putative pathway of glyconeogenesis in skeletal muscle. 729 90

The evolving concentration of metabolite intermediates for gluconeogenesis in liver and kidney has been studied in rats after varying periods of exercise (swimming in water at 22 degrees C). Lactate consumption by liver, according to the results, does not take place by gluconeogenesis primarily, since the values for malate, aspartate and PEP show a low in vivo activity for phosphoenolpyruvate carboxykinase. The PEP/aspartate ratio, on the contrary, gradually rises in kidney, suggesting a gradual increase in the in vivo activity of phosphoenolpyruvate carboxykinase, which agree quite well with the results of previously obtained in vitro. The prevention of metabolic acidosis by bicarbonate administration affects the metabolite profile in liver during exercise only very slightly. Renal phosphoenol-pyruvate carboxykinase activity in vivo decreases in relation to previously untreated rats, as well as gluconeogenesis, although to a lesser extent.
...
PMID:[Evolution of the content of gluconeogenic metabolites in rat liver and kidney during exercise (author's transl)]. 732 90

A method is described for the purification of the enzyme phosphoenolpyruvate carboxykinase (PEPCK) from the cestode Hymenolepis diminuta. When purified to electrophoretic homogeneity, the enzyme had a molecular weight of 70,600 and an isoelectric point of 7.5. Kinetic studies indicated that the pH 5.6 was optimal for the carboxylation reaction and that Mn++ was the preferred divalent cation; there was no activity of the enzyme in the presence of Mg++. Apparent Km values for the carboxylation reaction were determined; those for GDP (20.6 muM) and PEP (38.9 muM) were lower than the values previously reported. GTP, GMP, ITP, IMP, fumarate, succinate and alpha-ketoglutarate were found to be competitive inhibitors and their Ki values determined.
...
PMID:Purification and properties of phosphoenolpyruvate carboxykinase from Hymenolepis diminuta (Cestoda). 732 56

Despite the marked changes that crustacean muscle undergoes during the molt cycle, pyruvate kinase is present as the same form throughout the molt cycle. This pyruvate kinase was subject to feed-forward activation by fructose-1, 6 bisphosphate (FBP) as well as feed-back inhibition by MgATP. The enzyme showed a high affinity for phosphoenolpyruvate (Km = 0.1 mM) but showed no cooperativity in substrate binding. The addition of 0.05 mM FBP reduced the PEP Km to 0.05 mM. MgATP inhibition showed a Ki of 1.8 mM versus PEP. The inhibition due to MgATP could be reversed by FBP. Various other compounds inhibited the enzyme, including citrate, alpha-ketoglutarate, tryptophan, and malate, although at rather high levels. Measurements of the reversal of this pyruvate kinase, taken together with the low levels of phosphoenolpyruvate carboxykinase and pyruvate carboxylase, predict only minimal levels of gluconeogenic flux in crustacean muscle.
...
PMID:Catalytic and regulatory properties of muscle pyruvate kinase from Cancer magister. 746 68

An automated method for the determination of bicarbonate in human serum based on the enzymatic reaction between the analyte and phospho(enol)pyruvate (PEP) in the presence of PEP carboxylase is proposed. The analytical reaction is coupled with a derivatization reaction in which the NADH consumed is fluorimetrically monitored (lambda ex = 340 nm, lambda em = 460 nm). A stopped-flow/flow-injection approach is used in which the enzymes (PEP carboxylase and malate dehydrogenase) are immobilized on controlled-pore glass. The linear determination range is between 25 and 300 mmol/l (r2 = 0.9973). The %C.V. for the within- and between-run studies, performed at three concentration levels, ranges between 1.0 and 3.6% and the sampling frequency is 20 per h.
...
PMID:Enzymatic determination of bicarbonate in serum by flow injection analysis. 755 71

ATP-dependent phospho enol pyruvate carboxykinase (EC 4.1.1.49; PEPCK, ATP) was purified from glycosomes of cultured procyclic Trypanosoma brucei to electrophoretic homogeneity. The purified enzyme exhibited a mean specific activity of 83 units mg-1, as measured in the carboxylation direction at 30 degrees C. A similar activity was obtained for the decarboxylation reaction. The enzyme was shown to be a homodimer in solution with a subunit molecular mass of 59 kDa. Amino acid sequence analysis suggested that the PEPCK (ATP) is identical to the trypanosomal protein p60, the sequence of which was previously predicted from the corresponding nucleotide sequence by other investigators. The basic nature of the enzyme was indicated by a high isoelectric point (pH 8.9). The enzyme was found to be strictly dependent on adenosine nucleotides for activity, as well as on the presence of Mn2+. Mg2+ was found to be ineffective as activator of the trypanosomal enzyme, but a combination of subsaturating (< or = 300 microM) concentrations of Mn2+ and high concentrations of Mg2+ caused a synergistic effect on the carboxylation activity, indicating a dual cation requirement. Mn2+ is necessary to activate the enzyme and Mn2+ or Mg2+ most likely forms the cation-nucleotide complex as the active form of the substrate. Relatively high (5 mM) levels of ATP were required to produce a significant inhibition of the carboxylation reaction. Quinolinic acid, a structural analogue of oxaloacetate, completely inhibited the decarboxylation reaction at a 1 mM concentration. The apparent Michaelis constants of the enzyme were 490 microM for PEP, 37 microM for oxaloacetate, 40 microM for ADP, 10.3 microM for ATP, 970 microM for Mn2+ and 26 mM for HCO3-. Endogenous substrate concentrations were found to be 327 nmol PEP, 1486 nmol ADP, 4200 nmol ATP and 11.5 nmol Mn2+ (ml cell volume)-1. Our kinetic data suggest that under physiological conditions PEPCK (ATP) in T. brucei is bidirectional and that its activity is regulated primarily by mass action. The physiological relevance of the enzyme in procyclic T. brucei is discussed.
...
PMID:Purification and characterization of phospho enol pyruvate carboxykinase from Trypanosoma brucei. 776 79


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

---