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:6.4.1.1 (pyruvate carboxylase)
1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Oxaloacetate synthesis catalysed by pyruvate carboxylase from a thermophilic Bacillus in the absence of acetyl-CoA required addition of high concentrations of pyruvate, MgATP(2-) and HCO(3) (-), and at 45 degrees C occurred at a maximum rate approx. 20% of that in the presence of a saturating concentration of acetyl-CoA. The apparent K(m) for HCO(3) (-) at pH7.8 was 400mm without acetyl-CoA, and 16mm with a saturating activator concentration. The relationship between reciprocal initial rate and reciprocal MgATP(2-) concentration was non-linear (convex-down) in the absence of acetyl-CoA, but the extent of deviation decreased as the activator concentration was increased. The relationship between reciprocal initial rate and reciprocal pyruvate concentration was non-linear (convex-down) in the presence or absence of acetyl-CoA. 2. The optimum pH for catalysis of oxaloacetate synthesis was similar in the presence or absence of acetyl-CoA. The variation with pH of apparent K(m) for HCO(3) (-) implicated residue(s) with pK(a) 8.6 in catalysis of the activator-independent oxaloacetate synthesis. 3. Linear Arrhenius and van't Hoff plots were observed for the temperature-dependence of oxaloacetate synthesis in the absence of acetyl-CoA over the range 25-55 degrees C. E(a) (activation energy) was 56.3kJ/mol and DeltaH(double dagger) (HCO(3) (-)) (enthalpy of activation) was -38.6kJ/mol. In the presence of acetyl-CoA, biphasic Arrhenius and van't Hoff plots are observed with a change of slope at 30 degrees C in each case. E(a) was 43.7 and 106.3kJ/mol above and below 30 degrees C respectively. 4. Incubation of Bacillus pyruvate carboxylase with trinitrobenzenesulphonate caused specific inactivation of acetyl-CoA-dependent catalytic activity associated with the incorporation of 1.3+/-0.2 trinitrophenyl residues per subunit. Activator-independent catalysis and regulatory inhibition by l-aspartate were unaffected. The rate of inactivation of acetyl-CoA-dependent catalysis by trinitrobenzenesulphonate was specifically decreased by addition of acetyl-CoA and other acetyl-CoA and other acyl-CoA species, but complete protection was not obtained. 5. All alkylacyl derivatives of CoA tested activated Bacillus pyruvate carboxylase; acetyl-CoA was the most effective. The apparent K(a) exhibited a biphasic relationship with acyl-chain length for the straight-chain homologues. Certain long-chain acyl-CoA species showed additional activation at a high concentration. Weak activation occurred on addition of CoA or adenosine 3',5'-bisphosphate, but carboxyacyl-CoA species and derivatives containing a modified phosphoadenosyl group were inhibitory. Thioesters of CoA with non-carboxylic acids, e.g. methanesulphonyl-CoA, serve as activators of the thermophilic Bacillus and Saccharomyces cerevisiae pyruvate carboxylases, but as inhibitors of pyruvate carboxylases obtained from chicken and rat liver. 6. alpha-Oxoglutarate mimics the effect of l-aspartate as a regulatory inhibitor of the pyruvate carboxylases from both the thermophilic Bacillus and Saccharomyces cerevisiae. l-Glutamate was ineffective in both cases.
...
PMID:Pyruvate carboxylase from a thermophilic Bacillus. Studies on the specificity of activation by acyl derivatives of coenzyme A and on the properties of catalysis in the absence of activator. 2 48

1. Birds affected by fatty liver and kidney syndrome (FLKS) had elevated concentrations of serum Na+, K+, lactate, pyruvate and uric acid and reduced concentrations of serum HCO-3 and glucose. 2. Short-term treatment with biotin or animal tallow reduced the mortality from FLKS and prevented the clinical signs. 3. Lactic acidosis may be a major factor contributing to the mortality and physical symptoms observed in birds affected by FLKS. The lactic acidosis and the hypoglycaemia observed in FLKS are due primarily to an accumulation of pyruvate as a result of an insufficiency of biotin for normal pyruvate carboxylase activity.
...
PMID:Clinical signs of fatty liver and kidney syndrome in broilers and their alleviation by the short-term use of biotin or animal tallow. 59 40

Kinetic methods have been used to determine the interrelationship between HCO-3, pyruvate and acetyl-CoA and their effect on pigeon kidney pyruvate carboxylase (pyruvate: CO2 ligase [ADP], EC 6.4.1.1). HCO-3 shows a negative co-operative effect (biphasic kinetics with two different Km values). Pyruvate influences the attachment of HCO-3 to this enzyme. The same has been shown for acetyl-CoA. Contrary to the results of other investigators no co-operative effect was seen with pyruvate even at different concentrations of acetyl-CoA. HCO-3 itself shows hardly any effect on the homotropic positive co-operativity (sigmoidal kinetics) of acetyl-CoA. The negative co-operative effect of HCO-3 could not be removed even at saturating concentrations of pyruvate and/or acetyl-CoA, which is also supported by the n and Rs values. The results of this communication bring out differences between pigeon kidney pyruvate carboxylase and pyruvate carboxylase from other sources. It is also suggested that there may be different allosteric and regulatory sites for acetyl-CoA, HCO-3 and pyruvate.
...
PMID:Apparent co-operative effect of hydrogen carbonate (HCO-3) on pigeon kidney pyruvate carboxylase. 93 24

Cell-free extracts of Rhizopus arrhizus contain exclusively cytosolic pyruvate carboxylase and NAD-glutamate dehydrogenase, a single mitochondrial isoenzyme of NADP-isocitrate dehydrogenase, and both mitochondrial and cytosolic isoenzymes of NADP-malate dehydrogenase (decarboxylating). Other enzymes examined have sub-cellular localisations similar to those characteristic of mammalian liver. Purified preparations of R. arrhizus pyruvate carboxylase are subject to partial regulatory inhibition by L-aspartate and 2-oxoadipate. L-Glutamate acts as a less effective analogue of L-aspartate while 2-oxoglutarate is ineffective. Competition studies indicate the presence of separate inhibitory sites for L-aspartate and 2-oxoadipate. Under routine assay conditions R. arrhizus pyruvate carboxylase shows significant activation by acyl derivatives of coenzyme A with long chain acyl CoA being more effective than acetyl-CoA. This activation is no longer observed in the presence of high concentrations of pyruvate, MgATP2- and HCO-3. The concentrations of L-aspartate and 2-oxoadipate required to give 50% inhibition ([I]0.5), and the maximal extents of inhibition, are increased by addition of acetyl-CoA. Acetyl-CoA increases the sigmoidal character of the relationship: initial rate/[L-aspartate], but decreases this parameter for the relationship: initial rate/[2-oxoadipate]. The studies indicate that R. arrhizus possesses an entirely cytosolic pathway for the conversion of glucose to fumaric acid and that both the organisation of pyruvate metabolism and the regulation of pyruvate carboxylase differ significantly in this organism as compared to that proposed previously for Aspergillus nidulans.
...
PMID:The sub-cellular localisation and regulatory properties of pyruvate carboxylase from Rhizopus arrhizus. 397 71

1. The reaction pathway for the carboxylation of pyruvate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K(+) and acetyl-CoA. 2. Free Mg(2+) binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgATP(2-) binds next, followed by HCO(3) (-) and then pyruvate. Oxaloacetate is released before the random release, at equilibrium, of P(i) and MgADP(-). 3. This reaction pathway is compared with the double displacement (Ping Pong) mechanisms that have previously been described for pyruvate carboxylases from other sources. The reaction pathway proposed for the pig liver enzyme is superior in that it shows no kinetic inconsistencies and satisfactorily explains the low rate of the ATP[unk][(32)P]P(i) equilibrium exchange reaction. 4. Values are presented for the stability constants of the magnesium complexes of ATP, ADP, acetyl-CoA, P(i), pyruvate and oxaloacetate.
...
PMID:Pig liver pyruvate carboxylase. The reaction pathway for the carboxylation of pyruvate. 444 12

1. The reaction pathway for the decarboxylation of oxaloacetate, catalysed by pig liver pyruvate carboxylase, was studied in the presence of saturating concentrations of K(+) and acetyl-CoA. 2. Free Mg(2+) binds to the enzyme in an equilibrium fashion and remains bound during all further catalytic cycles. MgADP(-) and P(i) bind randomly, at equilibrium, followed by the binding of oxaloacetate. Pyruvate is released before the ordered steay-state release of HCO(3) (-) and MgATP(2-). 3. These results are entirely consistent with studies on the carboxylation of pyruvate presented in the preceding paper (Warren & Tipton, 1974b) and together they allow a quantitative description of the reaction mechanism of pig liver pyruvate carboxylase. 4. In the absence of other substrates of the back reaction pig liver pyruvate carboxylase will decarboxylate oxaloacetate in a manner that is not inhibited by avidin. 5. Reciprocal plots involving oxaloacetate are non-linear curves, which suggest a negatively co-operative interaction between this substrate and the enzyme.
...
PMID:Pig liver pyruvate carboxylase. The reaction pathway for the decarboxylation of oxaloacetate. 444 13

Anaplerotic fixation of carbon dioxide by the fungus Aspergillus nidulans when grown under carbon-limited conditions was mediated by pyruvate carboxylase and a phosphoenol pyruvate (PEP)-metabolising enzyme which has been tentatively designated as PEP carboxylase. The activities of both enzymes were growth rate dependent and measurements of H14CO3 incorporation by growing mycelium indicated that they were responsible for almost all the assimilated carbon dioxide. In carbon-limited chemostats, the maximum rate of bicarbonate assimilation occurred at a dilution rate of 0.11 h-1, equivalent to 1/2 micromax. The affinity of the pyruvate carboxylase for bicarbonate was twice that of the PEP carboxylase under the conditions of growth used. The effect of changing the bicarbonate concentration in carbon-limited chemostats was substantial: increasing the HCO-3 concentration over the range 0.7 - 2.8 mM enhanced biomass synthesis by 22%. Over-shoots in bicarbonate assimilation and carboxylase activity occurred when steady state chemostat cultures were subjected to a step down in dilution rate.
...
PMID:Anaplerotic metabolism of Aspergillus nidulans and its effect on biomass synthesis in carbon limited chemostats. 678

The co-existence of a hereditary defect of pyruvate carboxylase activity along with proximal renal tubular acidosis in several patients prompted the following theories: (1) Some of the bicarbonate which is normally reabsorbed from the glomerular filtrate is trapped in the mitochondria by pyruvate carboxylase in the conversion of pyruvate to oxaloacetate. The subsequent conversion of oxaloacetate to phosphoenol pyruvate releases CO2 in the cytosol. (2) The trapping of HCO-3 by pyruvate (or other carboxylases) provides an important route for the recovery of filtered HCO-3. (3) The process of trapping HCO-3 from the glomerular filtrate followed by release of CO2 in the cytosol contributes to the apparently high RQ of kidney, since the CO2 does not originate from a metabolic fuel. (4) Lactate and possibly other fuels are actively taken up by the kidney and are used as energy sources. Diversion of lactate for gluconeogenesis may contribute to the "excess substrate uptake" phenomenon. (5) It is possible that some of the glucose which is synthesized in the cortex is used for glycolysis in the medulla. Conversely, lactate produced in the medulla may be available to the cortex for bicarbonate trapping and thus for gluconeogenesis.
...
PMID:Is pyruvate carboxylase involved in the renal tubular reabsorption of bicarbonate? 678 31

There have been many fatal occupational accidents of skin exposure to monochloroacetic acid (MCA). However, there have been no reports of dermatological findings and the lethal consequences have not yet been demonstrated. Therefore, harmful local and systemic effects were investigated after dermal exposure to MCA. A 0.5 mL aliquot of MCA solution (40% w/w) was applied to the abdominal skin of ten 10-week-old male SD rats under anesthesia. The exposure area (25 x 25 mm2) was 1.6% of the total surface area. The dose of MCA per area was 34.1 mg/cm2. Saline was similarly administered to 10 control rats. Histopathological findings after 10 min were observed by light microscopy. Blood samples were collected by exsanguinations from the carotid arteries after 4 h. Skin samples were collected 10 min after the initial exposure. Histological findings showed severe degeneration of collagen bundles in the epidermis and subcutaneous tissues. P(CO2), HCO(3)-, TCO2, BE and glucose levels were decreased in the MCA group. AST, m-AST, ALT, BUN, Cr, NH3, lactic acid, pyruvic acid, RBC, Hb, Hct, total protein and albumin were increased in the MCA group. The burn was determined to be a third-degree burn on the basis of the histopathological findings. The severe toxicity was probably a consequence of the rapid permeability. Biochemical parameters were a consequence of hepatocellular injuries, renal dysfunction, dysglyconeogenesis and dysfunction of ammonia metabolism. MCA reportedly enters the TCA cycle and inhibits aconitase. MCA metabolites also inhibit pyruvate carboxylase in the gluconeogenesis pathway. Therefore, the important serum biochemical abnormalities such as hypoglycemia and lactic acidosis should be monitored to find the acute systemic disorders.
...
PMID:Systemic effects and skin injury after experimental dermal exposure to monochloroacetic acid. 1574 77

PC (pyruvate carboxylase) is a biotin-containing enzyme that catalyses the HCO(3)(-)- and MgATP-dependent carboxylation of pyruvate to form oxaloacetate. This is a very important anaplerotic reaction, replenishing oxaloacetate withdrawn from the tricarboxylic acid cycle for various pivotal biochemical pathways. PC is therefore considered as an enzyme that is crucial for intermediary metabolism, controlling fuel partitioning toward gluconeogenesis or lipogenesis and in insulin secretion. The enzyme was discovered in 1959 and over the last decade there has been much progress in understanding its structure and function. PC from most organisms is a tetrameric protein that is allosterically regulated by acetyl-CoA and aspartate. High-resolution crystal structures of the holoenzyme with various ligands bound have recently been determined, and have revealed details of the binding sites and the relative positions of the biotin carboxylase, carboxyltransferase and biotin carboxyl carrier domains, and also a unique allosteric effector domain. In the presence of the allosteric effector, acetyl-CoA, the biotin moiety transfers the carboxy group between the biotin carboxylase domain active site on one polypeptide chain and the carboxyltransferase active site on the adjacent antiparallel polypeptide chain. In addition, the bona fide role of PC in the non-gluconeogenic tissues has been studied using a combination of classical biochemistry and genetic approaches. The first cloning of the promoter of the PC gene in mammals and subsequent transcriptional studies reveal some key cognate transcription factors regulating tissue-specific expression. The present review summarizes these advances and also offers some prospects in terms of future directions for the study of this important enzyme.
...
PMID:Structure, mechanism and regulation of pyruvate carboxylase. 1861 15


1 2 Next >>

---