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)

Glutamate and aspartate are putative excitatory neurotransmitters in the central nervous system. The present study utilized novel monoclonal antibodies against fixative-modified glutamate and aspartate and polyclonal antisera against the amino acid synthesizing enzymes, glutaminase and aspartate aminotransferase, to analyze the distribution of these amino acids in the rodent midbrain periaqueductal gray. Glutamate-, aspartate-, glutaminase- and aspartate aminotransferase-like immunoreactive neurons, fibers and processes are present throughout the rostrocaudal length of the periaqueductal gray. Glutamate- and glutaminase-like immunoreactive neurons displayed a similar homogeneous pattern of distribution, being localized predominantly to the lateral and dorsal subdivisions of the periaqueductal gray. Co-localization experiments suggest that glutamate and glutaminase are in fact co-contained within the same PAG neurons. Aspartate aminotransferase-like immunoreactive neurons were distributed in a pattern similar to glutamate and glutaminase with the exception that fewer cells were stained in the dorsocaudal and the rostral third of the PAG. Aspartate-like immunoreactive neurons were less numerous than glutamate-like immunoreactive cells and were located in the lateral aspect of the PAG. These results demonstrate a specific and distinct distribution of glutamate and aspartate immunoreactive neurons and support recent data suggesting that glutamate and aspartate serve as excitatory neurotransmitters in the PAG.
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PMID:Localization of glutamate, glutaminase, aspartate and aspartate aminotransferase in the rat midbrain periaqueductal gray. 288 81

Cysteinesulfinate decarboxylase, purified from male rat livers and homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is resolved into five distinct enzyme species (isoforms) by gel isoelectric focusing. Since the isoforms are present in fresh liver homogenates and do not arise by proteolysis, the enzyme is apparently heterogeneous in vivo. Although female rat livers contain only 5% of the cysteinesulfinate decarboxylase activity of male livers, immunological and enzymatic studies indicate that the distribution of isoforms is similar in both sexes. Rat brain and kidney also contain multiple isoforms which are cross-reactive with polyclonal antibodies prepared to the liver enzyme. The enzyme exhibits a protomer Mr of 53,000, and the native enzyme is shown by cross-linking studies to be dimeric. Purified enzyme contains no carbohydrate or phosphate and does not bind excess pyridoxal 5'-phosphate. Two pools of enzyme activity are resolved preparatively by chromatofocusing chromatography and have been examined with respect to substrate and inhibitor specificity. Both pools are most active toward L-cysteinesulfinate and L-cysteinesulfonate. Aspartate, homocysteinesulfinate, homocysteinesulfonate, 2-amino-3-phosphonopropionate, and glutamate are decarboxylated at rates less than 1% of that observed with L-cysteinesulfinate; D-cysteinesulfinate is not decarboxylated but is an effective inhibitor. The enzyme isoforms cannot be distinguished on the basis of substrate affinity or specificity. The enzyme is irreversibly inactivated by the mechanism-based inhibitors beta-methylene-DL-aspartate and beta-ethylidene-DL-aspartate. beta-Ethylideneaspartate, in contrast to the beta-methylene derivative, does not inhibit aspartate aminotransferase, an enzyme also important in cysteinesulfinate metabolism. beta-Ethylidene aspartate or related beta-ethylidene compounds may be useful in selectively altering cysteinesulfinate metabolism in vivo.
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PMID:Multiple forms of rat liver cysteinesulfinate decarboxylase. 358 15

1. Glutamate dehydrogenase, aspartate transaminase and alanine transaminase were present in the gill, liver and muscle tissues of Periophthalmodon schlosseri and Boleophthalmus boddaerti. Both transaminases were found in the cytosol and mitochondria. 2. A complete purine nucleotide cycle was not present in the tissues studied. 3. Glutamine synthetase was not detected. Phosphate-dependent glutaminase was detected in both the cytosol and mitochondria. 4. Aspartate was the major substrate of ammoniagenesis in the mudskippers, though glutamate and glutamine were also oxidised. 5. Transdeamination was the major pathway for ammoniagenesis in the mudskippers studied.
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PMID:Ammoniagenesis in mudskippers Boleophthalmus boddaerti and Periophthalmodon schlosseri. 366 40

Aspartate: 2-oxoglutarate aminotransferase from the anaerobic protozoon Trichomonas vaginalis was purified to homogeneity and characterized. It is a dimeric protein of overall Mr approx. 100000. Only a single isoenzyme was found in T. vaginalis. The overall molecular and catalytic properties have features in common with both the vertebrate cytoplasmic and mitochondrial isoenzymes. The purified aspartate aminotransferase from T. vaginalis showed very high rates of activity with aromatic amino acids as donors and 2-oxoglutarate as acceptor. This broad-spectrum activity was restricted to aromatic amino acids and aromatic 2-oxo acids, and no significant activity was seen with other common amino acids, other than with the substrates and products of the aspartate: 2-oxoglutarate aminotransferase reaction. Co-purification and co-inhibition, by the irreversible inhibitor gostatin, of the aromatic amino acid aminotransferase and aspartate aminotransferase activities, in conjunction with competitive substrate experiments, strongly suggest that a single enzyme is responsible for both activities. Such high rates of aromatic amino acid aminotransferase activity have not been reported before in eukaryotic aspartate aminotransferase.
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PMID:Aspartate: 2-oxoglutarate aminotransferase from trichomonas vaginalis. Identity of aspartate aminotransferase and aromatic amino acid aminotransferase. 387 73

The fate of aspartic acid used for proline fermentation by Kurthia catenaforma was traced by using aspartic acid-U-(14)C. The radioactivities of proline and glutamic acid increased with the disappearance of aspartic acid. After 40 hr, aspartic acid disappeared from the medium and radioactive alpha-ketoglutaric acid was detected. The radioactivity of proline reached 44% of aspartic acid radioactivity at 40 hr. The specific radioactivities of these amino acids and of alpha-ketoglutaric acid supported the notion that proline is produced mainly from aspartic acid via alpha-ketoglutaric acid and glutamic acid. Since the levels of glutamic acid dehydrogenases (EC 1.4.1.2 and EC 1.4.1.4) were low in this organism, it appears that the nitrogen atom of aspartic acid enters proline by the action of aspartate aminotransferase (EC 2.6.1.1). The mechanism of proline production is discussed on the basis of the role of aspartic acid in this fermentation.
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PMID:Mechanism of proline production by Kurthia catenaforma. 501 17

Two isozymes of aspartate aminotransferase have been demonstrated biochemically. One isozyme is found in the mitochondrial fraction of the cytoplasm, the other ("soluble") in the supernatant. Both isozymes can be demonstrated by the cytochemical technique of Lee and Torack, as reported in the preceding report. Aldehyde fixation rapidly inactivates both isozymes, especially the soluble one. Inactivation can be delayed by addition of ketoglutarate to the fixative. The ketoglutarate probably competes with the fixative for the active site of the enzyme, thus protecting that region of the molecule. This enables adequate tissue preservation with enough remaining enzymatic activity to be demonstrated by the precipitation of oxaloacetate as the lead salt from a medium containing alpha-ketoglutaric acid aspartic acid, and lead nitrate. Electron-opaque material was found not only in mitochondria but, as the result of substrate protection, on the plasma membranes of many cells including erythrocytes and bacteria, the limiting membrane of peroxisomes, and the transverse tubular system of striated muscle. Occasional centrioles, neurotubules, tubules in the tails of spermatozoa, the A-I band junction in myofibrils of striated muscle, and the ground substance between cisternae of endoplasmic reticulum in intestinal goblet cells also showed precipitate. In all cases, replacement of L-aspartic acid by D-aspartic acid in the medium resulted in unstained sections. The sensitivity of extramitochondrial sites to fixation, the need of ketoglutarate as an agent for protecting the enzymatic activity during the fixation process, and the known presence of only soluble isozyme in erythrocytes indicate that enzymatic activity at these sites can be attributed to the soluble isozyme. Localization of the soluble isozyme on the plasma membrane may be related to possible involvement in depolarization phenomena, amino acid transport, or synthesis of plasma membrane-bound mucopolysaccharides.
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PMID:The ultrastructural localization of the isozymes of aspartate aminotransferase in murine tissues. 553 35

1. The utilization of amino acids for gluconeogenesis by rat liver develops in postnatal life, reaching maximum activity at the fifth day. 2. The activity of aspartate transaminase shows a similar trend in postnatal development and the increased activity appears to be due to the soluble enzyme. 3. The activity of alanine transaminase is low in foetal and postnatal rat liver and increases in activity at about the twentieth day. 4. Aspartate, glutamate and alanine make a major contribution to gluconeogenesis in the postnatal rat liver.
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PMID:Gluconeogenesis from amino acids in neonatal rat liver. 604 92

We measured amino acid contents in the brains of 11 patients with dominantly inherited cerebellar disorders. Despite clinical similarities, three biochemically different disorders were found. One disorder, with demonstrated HLA linkage in one pedigree, was characterized by moderate reduction of aspartate and glutamate contents in cerebellar cortex alone. In a second disorder, aspartate and glutamate contents were reduced markedly in other brain areas as well as in cerebellar cortex. Aspartate and glutamate contents were normal in cerebellar cortex in the third disorder. GABA content in cerebellar cortex and dentate nucleus was reduced in some patients with each disorder, whereas cerebellar taurine content was normal in all patients. Aspartate deficiency in cerebellar cortex did not result from lack of aspartate aminotransferase or pyruvate carboxylase activity. These amino acid abnormalities probably imply loss of specific cerebellar neurons.
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PMID:Neurotransmitter amino acids in dominantly inherited cerebellar disorders. 611 Oct 44

Metabolism of the glutamate group of amino acids--glutamic acid, gamma-amino-butyric acid, glutamine, aspartic acid and alanine--was studied in the brain of rat as a function of age. The levels of glutamic acid, glutamine and aspartic acid decreased while those of gamma-aminobutyric acid, and alanine increased with age. The results on the activity of the twelve enzymes involved in the metabolism showed that five of them (glutamate dehydrogenase, glutamine synthase, gamma-aminobutyric acid transaminase, succinic semialdehyde dehydrogenase and NAD+-isocitrate dehydrogenase) decreased, while four of them (glutaminase, glutamotransferase, glutamic acid decarboxylase, and alpha-ketoglutarate dehydrogenase) increased. The other three enzymes (aspartate aminotransferase, alanine aminotransferase and NADP+-isocitrate dehydrogenase) did not show any significant change in activity. An age-related increase was seen in alpha-ketoglutarate and ammonia, the intermediates involved in the metabolism of these amino acids. The changes in the level of these amino acids are discussed in relation to the altered energy metabolism during aging.
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PMID:Metabolism of the glutamate group of amino acids in rat brain as a function of age. 614 62

Aspartate: 2-oxoglutarate aminotransferase [EC 2.6.1.1] was purified and crystallized from bakers' yeast. The crystalline preparation gave a single band on polyacrylamide disc gel electrophoresis in the presence of sodium dodecyl sulfate. However, in the absence of sodium dodecyl sulfate, the preparation gave one major band with two faint bands, all of which showed the same specific activity, molecular weight and serological properties. These faint bands appeared to be modified forms produced from the major band during the purification. The enzyme showed a molecular weight of 90,000 +/- 8,000 and 92,000 +/- 8,000 by gel filtration and sedimentation equilibrium analysis, respectively. The molecular weight of a subunit was estimated to be 45,000 by sodium dodecyl sulfate slab gel electrophoresis. Each subunit bound approximately 1 mol of pyridoxal 5'-phosphate. The bound pyridoxal 5'-phosphate showed an absorption maximum at 360 nm (epsilon M: 11,500) and 430 nm (epsilon M: 8,200) in alkaline and acidic conditions, respectively. Its proteolytic pK was pH 6.3. The enzyme showed an optimum pH of 8.0-9.0, and fairly high amino donor and acceptor specificities; aromatic amino acids and their corresponding 2-oxoacids were catalyzed at rates of 0.2-0.8% of those for aspartate and oxalacetate, respectively. Michaelis constants for various substrate were: L-aspartate (0.11 mM), L-glutamate (20.0 mM), oxalacetate (0.006 mM), and 2-oxoglutarate (0.16 mM). The antiserum against yeast aspartate aminotransferase did not form precipitin bands with homogeneous aspartate aminotransferases from pig heart cytosol, pig heart mitochondria or Escherichia coli B.
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PMID:Aspartate: 2-oxoglutarate aminotransferase from bakers' yeast: crystallization and characterization. 681 76


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