Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracts of the leaf tissue of Panicum maximum Jacq. var. trichoglume Eyles (a phosphoenolpyruvate carboxykinase type of C4 plant) were examined and at least two isoforms of aspartate aminotransferase (EC 2.6.1.1), with different electrophoretic mobilities, were detected. The predominant isoform was purified to homogeneity from mesophyll cells. The purification procedure included fractionation with ammonium sulfate followed by chromatography on diethylaminoethyl-cellulose, Sephacryl S-300, and hydroxyapatite. The purified enzyme had specific activities of 182 and 165 mumol/min/mg protein, measured in terms of the synthesis of oxaloacetate and aspartate, respectively, at pH 8.0. The enzyme, with an apparent molecular size of 100 kDa, appears to be a dimer of a single polypeptide with a molecular size of 42 kDa. Mono specific polyclonal antibodies were raised against the 42-kDa polypeptide. Only a single stained band was detected in extracts of whole leaves by immunoblot analysis with this antibody after two-dimensional polyacrylamide electrophoresis. Furthermore, no difference in mobility was observed between the enzymes extracted from mesophyll and bundle sheath cells on native polyacrylamide gels. These findings are discussed in relation to the other isoform in the leaves of this species.
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PMID:Aspartate aminotransferase from Panicum maximum Jacq. var. trichoglume Eyles, a C4 plant: purification, molecular properties, and preparation of antibody. 293 Jan 93

Both ammonia and beta-methylene-DL-aspartate (beta-MA), an irreversible inhibitor of aspartate aminotransferase activity and thus of the malate-aspartate shuttle, were found previously to decrease oxidative metabolism in cerebral cortex slices. In the present work, the possibility that ammonia and beta-MA affect energy metabolism by a common mechanism (i.e., via inhibition of the malate-aspartate shuttle) was investigated using primary cultures of neurons and astrocytes. Incubation of astrocytes for 30 min with 5 mM beta-MA resulted in a decreased production of 14CO2 from [U-14C]glucose, but did not affect 14CO2 production from [2-14C]pyruvate. Conversely, incubation of astrocytes with 3 mM ammonium chloride resulted in decreased 14CO2 production from [2-14C]pyruvate, but 14CO2 production from [U-14C]glucose was not significantly affected. Ammonium chloride had no significant effect on 14CO2 production from either [U-14C]glucose or [2-14]pyruvate by neurons. However, incubation of neurons with beta-MA or beta-MA plus ammonium chloride resulted in a approximately 45% decrease of 14CO2 production from both [U-14C]glucose and [2-14C]pyruvate. A 2-h incubation of astrocytes with beta-MA resulted in no change in ATP levels, but a 35% decrease in phosphocreatine. Similar treatment of neurons resulted in greater than 50% decrease in ATP, but had little effect on phosphocreatine. beta-MA also caused a decrease in glutamate and aspartate content of neurons, but not of astrocytes. The different metabolic responses of neurons and astrocytes towards beta-MA were probably not due to a differential inhibition of aspartate aminotransferase which was inhibited by approximately 45% in astrocytes and by approximately 55% in neurons.
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PMID:Effects of ammonia and beta-methylene-DL-aspartate on the oxidation of glucose and pyruvate by neurons and astrocytes in primary culture. 313 86

The effect of hypoxia and post-hypoxic recovery were studied in gastrocnemius muscle of young-adult and mature beagle dogs. Furthermore, the possible interference of pharmacological treatment with nicergoline was evaluated in these conditions. Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose 6-phosphate, pyruvate, lactate), Kreb's cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate) and related free amino acids (glutamate, alanine), ammonium ion, energy store and mediators (ATP, ADP, AMP and creatine phosphate), and the energy charge potential were evaluated. Furthermore, in the crude extract and/or mitochondrial fraction of another portion of the same gastrocnemius muscle the maximum rate (Vmax) of some muscular enzymes related to the anaerobic glycolytic pathway (hexokinase, lactate dehydrogenase), the Kreb's cycle (citrate synthase, malate dehydrogenase), the aminoacid pool related to the Krebs' cycle (glutamate dehydrogenase and aspartate aminotransferase), the electron transfer chain (cytochrome oxidase) and NAD+/NADH exchanges (total NADH cytochrome c reductase) was evaluated. Some glycolytic metabolites and Krebs' cycle intermediates were modified by acute hypoxia, while free amino acids and energy mediators remained practically unchanged. The pharmacological treatment maintained the glucose and succinate muscular concentrations within the normal range, during hypoxia. The behaviour of muscular metabolites during hypoxia and/or post-hypoxic recovery is an age-related event. In fact, only in young-adult animals did the altered values return to normal in post-hypoxic recovery. In the present experimental conditions, only minor changes were observed as far as muscular enzyme activities are concerned. In any case, some enzyme activities tested showed different Vmax in young-adult dogs in comparison with mature ones.
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PMID:Effect of hypoxia, aging and pharmacological treatment on muscular metabolites and enzyme activities. 322 9

Cytosolic and mitochondrial isoenzymes of aspartate aminotransferase (EC 2.6.1.1) were purified to homogeneity from chicken liver, without previous fractionation of the subcellular components. The procedure includes initial heat treatment and ammonium sulfate fractionation. The two isoenzymes can then be separated by a DEAE-Sepharose chromatography using a linear gradient of L-aspartate (reaction substrate). The separated fractions can be further purified by a parallel step with HA-Ultrogel prior to octyl-Sepharose (c-AAT) and CM-Sepharose (m-AAT) chromatographies. Michaelis constants, pI values, inhibition by adipate and subforms generation with time were studied for both isoenzymes.
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PMID:Simultaneous purification and characterization of aspartate aminotransferase isoenzymes from chicken liver. 323 18

The spatial structure of cytosolic chicken aspartate aminotransferase (AAT) has been determined by X-ray crystallographic analysis at 2.8 A resolution. AAT consists of two chemically identical subunits. Each subunit can be subdivided into the large pyridoxal phosphate (PLP) binding domain and the small domain. The two active sites of AAT are situated in deep clefts at the subunit interface. The binding of PLP and 2-oxoglutarate is described. Conformations of the following enzyme forms have been compared by difference Fourier syntheses: the nonliganded PLP-form in phosphate and acetate buffers; the non-liganded pyridoxamine phosphate (PMP) form; complexes of the PLP-form with glutarate and 2-oxoglutarate. Lattice-induced dynamic asymmetry of the dimeric AAT molecules was revealed. In one subunit the small domain is mobile and shifted either toward the active site ("closed" conformation) or in the opposite direction ("open" conformation). The closed conformation is induced by the binding of dicarboxylate anions. In the second subunit the small domain is immobile and shifted toward the active site in all enzyme forms or complexes studied. In this subunit, there occurs a rotation of the PLP ring by approximately 20 degrees toward the substrate site. The rotation is observed when crystals are soaked in 0.6 saturated (NH4)2SO4 solution buffered with 0.3 M potassium phosphate, pH 7.5; it was explained by formation of an external aldimine between PLP and NH3. This aldimine is not formed in the presence of dicarboxylates or acetate. It was inferred that dicarboxylate or acetate anions stabilize the internal PLP-lysine aldimine and prevent its reaction with ammonia. Conversion of AAT from the PLP- to PMP-form is accompanied by rotation of the coenzyme ring by approximately 20 degrees; the rotation occurs in both subunits.
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PMID:[Cytosol aspartate aminotransferase from the chicken heart: three-dimensional structure at 2.8 angstroms resolution and the characteristic conformation of various enzyme forms]. 398 8

1. A method is described for extracting separately mitochondrial and extramitochondrial enzymes from fat-cells prepared by collagenase digestion from rat epididymal fat-pads. The following distribution of enzymes has been observed (with the total activities of the enzymes as units/mg of fat-cell DNA at 25 degrees C given in parenthesis). Exclusively mitochondrial enzymes: glutamate dehydrogenase (1.8), NAD-isocitrate dehydrogenase (0.5), citrate synthase (5.2), pyruvate carboxylase (3.0); exclusively extramitochondrial enzymes: glucose 6-phosphate dehydrogenase (5.8), 6-phosphogluconate dehydrogenase (5.2), NADP-malate dehydrogenase (11.0), ATP-citrate lyase (5.1); enzymes present in both mitochondrial and extramitochondrial compartments: NADP-isocitrate dehydrogenase (3.7), NAD-malate dehydrogenase (330), aconitate hydratase (1.1), carnitine acetyltransferase (0.4), acetyl-CoA synthetase (1.0), aspartate aminotransferase (1.7), alanine aminotransferase (6.1). The mean DNA content of eight preparations of fat-cells was 109mug/g dry weight of cells. 2. Mitochondria showing respiratory control ratios of 3-6 with pyruvate, about 3 with succinate and P/O ratios of approaching 3 and 2 respectively have been isolated from fat-cells. From studies of rates of oxygen uptake and of swelling in iso-osmotic solutions of ammonium salts, it is concluded that fat-cell mitochondria are permeable to the monocarboxylic acids, pyruvate and acetate; that in the presence of phosphate they are permeable to malate and succinate and to a lesser extent oxaloacetate but not fumarate; and that in the presence of both malate and phosphate they are permeable to citrate, isocitrate and 2-oxoglutarate. In addition, isolated fat-cell mitochondria have been found to oxidize acetyl l-carnitine and, slowly, l-glycerol 3-phosphate. 3. It is concluded that the major means of transport of acetyl units into the cytoplasm for fatty acid synthesis is as citrate. Extensive transport as glutamate, 2-oxoglutarate and isocitrate, as acetate and as acetyl l-carnitine appears to be ruled out by the low activities of mitochondrial aconitate hydratase, mitochondrial acetyl-CoA hydrolyase and carnitine acetyltransferase respectively. Pathways whereby oxaloacetate generated in the cytoplasm during fatty acid synthesis by ATP-citrate lyase may be returned to mitochondria for further citrate synthesis are discussed. 4. It is also concluded that fat-cells contain pathways that will allow the excess of reducing power formed in the cytoplasm when adipose tissue is incubated in glucose and insulin to be transferred to mitochondria as l-glycerol 3-phosphate or malate. When adipose tissue is incubated in pyruvate alone, reducing power for fatty acid, l-glycerol 3-phosphate and lactate formation may be transferred to the cytoplasm as citrate and malate.
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PMID:The intracellular localization of enzymes in white-adipose-tissue fat-cells and permeability properties of fat-cell mitochondria. Transfer of acetyl units and reducing power between mitochondria and cytoplasm. 439 82

The mechanism of ammonia assimilation in Methanosarcina barkeri and Methanobacterium thermoautotrophicum was documented by analysis of enzyme activities, 13NH3 incorporation studies, and comparison of growth and enzyme activity levels in continuous culture. Glutamate accounted for 65 and 52% of the total amino acids in the soluble pools of M. barkeri and M. thermoautotrophicum. Both organisms contained significant activities of glutamine synthetase, glutamate synthase, glutamate oxaloacetate transaminase, and glutamate pyruvate transaminase. Hydrogen-reduced deazaflavin-factor 420 or flavin mononucleotide but not NAD, NADP, or ferredoxin was used as the electron donor for glutamate synthase in M. barkeri. Glutamate dehydrogenase activity was not detected in either organism, but alanine dehydrogenase activity was present in M. thermoautotrophicum. The in vivo activity of the glutamine synthetase was verified in M. thermoautotrophicum by analysis of 13NH3 incorporation into glutamine, glutamate, and alanine. Alanine dehydrogenase and glutamine synthetase activity varied in response to [NH4+] when M. thermoautotrophicum was cultured in a chemostat with cysteine as the sulfur source. Alanine dehydrogenase activity and growth yield (grams of cells/mole of methane) were highest when the organism was cultured with excess ammonia, whereas growth yield was lower and glutamine synthetase was maximal when ammonia was limiting.
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PMID:Ammonia assimilation and synthesis of alanine, aspartate, and glutamate in Methanosarcina barkeri and Methanobacterium thermoautotrophicum. 612 78

Eleven soluble enzymes in the supernatant of bloodstream Trypanosoma brucei were compared for electrophoretic mobility and activity with those of T. brucei cultures grown in 3 different media. All bands of each enzyme found in the bloodstream form were also present in the cultured material, but extra bands of malate dehydrogenase (MDH) (EC 1.1.1.37), aspartate aminotransferase (ASAT) (EC 2.6.1.1), and in 2 to 6 cultures of isocitrate dehydrogenase (ICD) (EC 1.1.1.42) were present in culture forms but not in bloodstream forms. An interfering enzyme, peculiar to cultured T. brucei, which reacted with 2-oxoglutarate and possibly a trace amount of ammonium ions, ran with the fast-moving ASAT bands. Threonine dehydrogenase activity, high in cultured trypanosomes irrespective of the medium used but low in bloodstream trypanosomes, was markedly lower in Trypanosoma evansi and a much passaged T. brucei 8/18. Glucosephosphate isomerase activity on the other hand was high in bloodstream and low in cultured trypanosomes. Glutamate dehydrogenase activity was too low to record reliably in bloodstream trypanosomes, but could be clearly detected in cultured forms. As the differences point to some changes in gene expression between the two forms, culture material is likely to replace trypanosomes from living animals for electrophoretic characterization only when considerable comparative work has been done.
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PMID:The electrophoretic mobilities and activities of eleven enzymes of bloodstream and culture forms of Trypanosoma brucei compared. 645 Aug 96

Glutamate dehydrogenase (GDH) and the transaminases namely aspartate aminotransferase (AAT) and alanine aminotransferase (AIAT) were estimated in the muscle, liver, kidney, and brain of control and ammonium acetate administered frogs. The results indicated tissue specific responses during induced ammonotoxemia. The inherent endogenous ammonia production decreased in all the tissues. 2-Keto glutarate production appears to be the other main adaptive feature as a result of slightly stepped up transdeamination patterns.
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PMID:Transamination and glutamate deamination in Rana hexadactyla during induced ammonia toxicity. 651 Oct 61

Carbamyl phosphate synthase-I can enhance glutamate dehydrogenase-mitochondrial aspartate aminotransferase interactions. These results indicate that a complex can be formed between all three enzymes, which is stable in the presence of substrates and modifiers of these enzymes and consequently can convert NH4+ produced from aspartate into carbamyl phosphate. Citrate can remove both the aminotransferase and glutamate dehydrogenase from this complex, while malate primarily removes glutamate dehydrogenase. This suggests that these metabolites play a role in determining if these enzymes interact with carbamyl phosphate synthase-I or with enzymes of the Krebs cycle. Since the level of carbamyl phosphate synthase-I is quite high in liver mitochondria, these results suggest that this enzyme plays a major role in placing the aminotransferase and glutamate dehydrogenase in close proximity.
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PMID:Aminotransferase-glutamate dehydrogenase-carbamyl phosphate synthase-I interactions. 671 17


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