Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.1 (aspartate aminotransferase)
 21,665 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Amino acids of the glutamate family, viz. glutamic acid, aspartic acid, glutamine, gamma-amino-butyric acid (GABA) and alanine, along with the activities of glutamic acid dehydrogenase (GDH), aspartic acid aminotransferase (AST), alanine aminotransferase (ALT), glutamine synthetase (GS), glutaminase, glutamic acid decarboxylase (GAD) and GABA-aminotransferase (GABA-T) were estimated in cerebral cortex, cerebellum and brain stem of rats treated with a single dose of lithium or with seven daily doses of lithium (3 m-equiv./kg body wt). The levels of GABA were found to increase in cerebral cortex and brain stem following the administration of a single dose and also were found to be increased in cerebral cortex and cerebellum after treatment for 7 days. The content of glutamic acid was increased in all three brain regions after treatment for 7 days. Glutamine was increased in both cerebral cortex and brain stem after treatment for 7 days, whereas aspartic acid was increased in brain stem after both the administration of single dose and treatment for 7 days. A significant increase (P less than 0.05) in the activity of GS was observed in brain stem after 7 days of treatment. Similarly, a significant increase (P less than 0.01) in the activity of AST was observed in all three regions of the brain following the treatment for 7 days. The above results are discussed in relation to the known effects of lithium on brain cation metabolism and a suggestion is made that an imbalance in the functional activities of glutamic acid and GABA as a result of quantitative changes in these amino acids, brought about by lithium, may play a role in the therapeutic efficacy of lithium in bipolar disorders.
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PMID:Acute and short-term effects of lithium on glutamate metabolism in rat brain. 286 24

Increased concentration of the excitatory neurotransmitter aspartic acid in actively spiking human epileptic cerebral cortex was recently described. In order to further characterise changes in the aspartergic system in epileptic brain, the behaviour of aspartic acid aminotransferase (AAT), a key enzyme involved in aspartic acid metabolism has now been examined. Electrocorticography performed during surgery was employed to identify cortical epileptic spike foci in 16 patients undergoing temporal lobectomy for intractable seizures. Patients with spontaneously spiking lateral temporal cortex (n = 8) were compared with a non-spiking control group (n = 8) of patients in whom the epileptic lesions were confined to the hippocampus sparing the temporal convexity. Mean activity of AAT in spiking cortex was significantly elevated by 16-18%, with aspartic acid concentration increased by 28%. Possible explanations for the enhanced AAT activity include increased proliferation of cortical AAT-containing astrocytes at the spiking focus and/or a generalised increase in neuronal or extraneuronal metabolism consequent to the ongoing epileptic discharge. It is suggested that the data provide additional support for a disturbance of central excitatory aspartic acid mechanisms in human epileptic brain.
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PMID:Aspartic acid aminotransferase activity is increased in actively spiking compared with non-spiking human epileptic cortex. 289 10

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

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

Cysteine aminotransferase (L-cysteine: 2-oxoglutarate aminotransferase, EC 2.6.1.3) was purified over 400-fold from the high-speed supernatant fraction of rat liver. The purified enzyme was homogeneous as judged by gel filtration, isoelectric focusing and disc electrophoresis. The molecular weight of the enzyme was about 74,000 by gel filtration and the isoelectric point was 6.2 (4 degrees C). The enzyme catalyzed transamination between L-cysteine and 2-oxoglutarate and the reverse reaction. The optimum pH was 9.7. The Km value for L-cysteine was 22.2 mM, and that for 2-oxoglutaric acid was 0.06 mM. L-Aspartate was a potent inhibitor of the cysteine aminotransferase reaction. The enzyme was very active toward L-alanine 3-sulfinic acid at pH 8.0, and was also very active toward L-aspartic acid (Km = 1.6 mM). Ratios of activities for L-aspartic acid and L-cysteine were essentially constant during the purification of the enzyme. Evidence based on substrate specificity, enzyme inhibition, and physicochemical properties indicates that cytosolic cysteine aminotransferase is identical with cytosolic aspartate aminotransferase (L-aspartate: 2-oxoglutarate aminotransferase, EC 2.6.1.1).
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PMID:Purification and characterization of cysteine aminotransferase from rat liver cytosol. 711 43

Maackia amurensis haemagglutinin (MAH) is a leguminous lectin which preferentially binds to a cluster of sialylated O-linked carbohydrate chains (Konami Y, Yamamoto K. Osawa T, Irimura T (1994) FEBS Lett 342:334-38). In the present study a 950 bp cDNA clone encoding MAH was isolated from a cDNA library constructed from germinated Maackia amurensis seeds. From the nucleotide sequence, MAH was predicted to consist of 285 amino acid residues containing a signal peptide of 29 amino acids. The results also confirmed our previous findings from the amino acid sequence analysis, which indicated that two highly conserved amino acid residues in all other well-known leguminous lectins were replaced in MAH. These residues were lysine-105 and aspartic acid-135. The corresponding amino acid residues in other leguminous lectins were glycine and asparagine, respectively. These differences were due to the presence of nucleotides AAA and GAT in place of AAT/C and GGA/T.
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PMID:Cloning and sequence analysis of the Maackia amurensis haemagglutinin cDNA. 769 60

L-asparaginase and L-aspartate aminotransferase are both involved in the synthesis of L-aspartic acid. It has been observed that L-asparaginase is involved in the immunosuppressor morphine-dependent syndrome in lymphoid cells whereas L-aspartic acid blocks the development of this syndrome. The aim of the present study was to clarify the localization of L-AATase activity and L-asparaginase in rat lymph nodes using histoenzymological and immunohistochemical methods, respectively. No positive reaction was demonstrated for L-AATase while L-asparaginase shown to be present in lymphocytes and lymphoblastic cells. These observations lead us to suggest that L-asparaginase is the enzyme mainly responsible for the synthesis of the L-aspartic acid necessary for satisfying the living requirements of lymphoid cells. Therapeutically administered L-asparaginase could exert its action intracellularly after crossing the cell membrane.
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PMID:L-aspartate aminotransferase and L-asparaginase in rat lymph node: a histoenzymological and immunohistochemical study. 863 Apr 37

Three hemoglobin variants (Hb Nancy, Osler and Fort Gordon), carrying the same Tyr-->Asp substitution at position beta 145 (HC2), have been independently described in 1975 in patients with marked polycythemia. The first one was found in a French caucasian family from Lorraine, and the two others in African Americans. Two unrelated individuals with Hb Osler have been recently reinvestigated at the DNA level and surprisingly, in their beta gene, codon 145 was found to be AAT which encodes for asparagine and not for aspartic acid, the aspartate at the protein level resulting, thus, from a very efficient posttranslational event. We reinvestigated a patient from the family of Hb Nancy and found that codon 145 was GAT, encoding for aspartate. This demonstrates that Hb Nancy is genetically distinct from Hb Osler despite an almost identical phenotype.
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PMID:Hb Nancy and Hb Osler: two distinct genetic variants with identical clinical and hemoglobin phenotype. 976 88

Excitatory amino acids (EAAs), in particular, L-aspartate (L-Asp) neurons and their processes, were localized in the rat stomach using a immunohistochemical method with specific antibodies against either L-Asp or its synthesizing enzyme, aspartate aminotransferase (AAT). Myenteric ganglia and nerve bundles in the circular muscle and in the longitudinal muscle were found to be AAT- or L-Asp-positive. In addition, AAT- or L-Asp-positive cells were also found in the muscle layer and the deep mucosal layer. The distribution of AAT- or L-Asp-positive cells in both the mucosal and muscle layers was heterogeneous in the stomach. In addition, L-Asp at 10(-6) M negligibly influenced acid secretion in an everted preparation of isolated rat stomach. However, according to our results, L-Asp markedly inhibited the histamine-stimulated acid secretion, but not the oxotremorine- or the pentagastrin-stimulated acid secretion. Furthermore, L-Asp also inhibited histamine-induced elevation of cAMP. L- Asp itself did not affect the cAMP level although it elevated the cGMP level in the stomach. Moreover, either (+)2-amino-5-phosphonovaleric acid or (+/-)3-(2-carboxypiperazin-4-yl)prophyl-1-phosphonic acid, i.e. two specific antagonists for N-methyl-D-aspartic acid (NMDA) receptors, blocked the inhibitory effect of L-Asp on histamine-stimulated acid secretion or histamine-induced elevation of cAMP. Since cAMP has been strongly implicated as the second messenger involved in histamine-induced acid secretion, we believe that L-Asp regulates acid secretion in the stomach by inhibiting histamine release through the NMDA receptors, subsequently lowering the level of cAMP and ultimately reducing acid secretion.
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PMID:Effect of excitatory amino acid neurotransmitters on acid secretion in the rat stomach. 993 41


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