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

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Query: EC:2.6.1.19 (GABA transaminase)
808 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The contents of gamma-aminobutyric acid (GABA) and glutamate (GL) as well as GABA-aspartate- and alanine aminotransferase activities were measured in rat cerebellum, cerebral cortex and truncus cerebri 1, 3, 6, 24 and 48 hr following total-body gamma-irradiation (60Co) with a dose of 30 Gy. All the indices under study changed in a similar way in the cortex and truncus cerebri while in the cerebellum, GABA level increased and GABA-alpha-ketoglutarate aminotransfearse activity decreased 60 min after irradiation. The levels of GABA and GL in the cortex and truncus cerebri decreased immediately and increased 24 hr after irradiation. Activity of aminotransferases changed in a phase manner: changes in aspartate- and alanine aminotransferase activity were more pronounced than those of GABA-alpha-ketoglutarate aminotransferase activity and correlated with the glutamate level changes.
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PMID:[Early changes in GABA and glutamate levels and aminotransferase activity in parts of the rat brain following whole-body gamma irradiation at an absolutely lethal dose]. 389 85

The concentrations of GABA, glutamate, serine, glutamine, threonine, glycine and taurine in the substantia nigra and in the corpus striatum of the rat were determined electrochemically following condensation with o-phthalaldehyde-beta-mercaptoethanol and reverse-phase, high performance liquid chromatography. After a frontal hemisection at the level of the caudal hypothalamus, the GABA concentration in the substantia nigra on the operated side decreased to about 20 per cent of the normal value in 4 days, in all probability caused by degeneration of the nerve terminals of the striato-nigral GABA neurons. The concentrations of taurine in the substantia nigra and of GABA in the corpus striatum were initially lowered and later elevated following this lesion. The concentration of glutamate in the substantia nigra was lower on the sectioned side and higher on the intact side at 14 days as compared to 4 hours after a hemisection. Following an acute hemisection, the GABA transaminase inhibitor gamma-acetylenic GABA increased the concentration of GABA by 36% and 79% in the substantia nigra on the sectioned and intact side, respectively. The glutamate decarboxylase inhibitors 4-deoxypyridoxine and isoniazid lowered the concentration of GABA in the substantia nigra by about 50% on both the sectioned and intact side. The results indicate that the synthesis, but not the utilization of GABA in the substantia nigra is dependent on the normal nerve impulse flow. The concentration of glutamine was changed in directions contrary to that of GABA following a chronic hemisection or treatment with gamma-acetylenic GABA, in agreement with the suggestion that glutamine is a precursor of the GABA transmitter pool.
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PMID:Effect of the normal nerve impulse flow on the synthesis and utilization of GABA in the rat substantia nigra. 398 Nov 61

Goldfish retinas incubated with L-glutamate-(14)C (UL) were found to synthesize gamma-aminobutyric acid-(14)C (GABA-(14)C) The accumulation of newly synthesized GABA was enhanced by physiological stimulation of the retina with flashing light; and this increase was directly proportional to the logarithm of the light intensity. The total GABA content was also higher in light-stimulated than in dark-adapted retinas, although the glutamate content remained unchanged No differences were found in the cell-free activities of glutamate decarboxylase (EC 4 1.1 15) and GABA-glutamate transaminase (EC 2.6.1.19) extracted from light-stimulated and dark-adapted retinas. These findings, together with other physiological and morphologcal evidence, suggest that GABA plays a functional role in synaptic transmission in the goldfish retina
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PMID:The biosynthesis and content of gamma-aminobutyric acid in the goldifsh retina. 433 78

Mutants of Escherichia coli K-12 isolated for their ability to utilize gamma-aminobutyrate (GABA) as the sole source of nitrogen exhibit a concomitant several-fold increase in the activities of gamma-aminobutyrate-alpha-ketoglutarate transaminase (GSST, EC 2.6.1.19) and succinic semialdehyde dehydrogenase (SSDH, EC 1.2.1.16). The increase in rate of enzymatic activity is not accompanied by any changes in the affinities of the mutant enzymes for their respective substrates. The synthesis of the two enzymes is highly coordinate under a great variety of conditions, in spite of the wide range of activities observed. In cultures grown in minimal media with ammonium salts as the source of nitrogen, both GSST and SSDH are severely repressed by glucose. Substitution of ammonia with GABA, glutamate, or aspartate greatly reduces the effect of glucose on the synthesis of the GABA utilization enzymes. This escape from catabolite repression is specific for GSST and SSDH and does not involve other enzymes sensitive to catabolite repression (e.g., beta-galactosidase, EC 3.2.1.23, and aspartase, EC 4.3.1.1).
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PMID:Control of the pathway of -aminobutyrate breakdown in Escherichia coli K-12. 455 85

1. Rat retinae pre-incubated and incubated at 37 degrees C in media containing amino-oxyacetic acid (AOAA) (0.1 muM to 1 mM) accumulated more (3)H-gamma-aminobutyric acid ((3)H-GABA) than control retinae incubated in the absence of AOAA. This increased accumulation of (3)H-GABA by tissue exposed to AOAA was not apparent at short incubation times (0-20 min), but became significant after incubations of 30 min, and maximal after incubation for 60 minutes.2. At a concentration of 10 muM, AOAA did not alter the apparent K(m) for (3)H-GABA uptake or V(max) for either the low or the high affinity GABA uptake systems present in retina.3. The potentiation of (3)H-GABA accumulation produced by AOAA appeared to parallel the inhibitory effect of this compound on 2-oxoglutarate-4-aminobutyrate aminotransferase (GABA-T). Similarly, hydrazinopropionic acid inhibited retinal GABA-T and potentiated the accumulation of (3)H-GABA, but hydroxylamine and thiosemicarbazide which did not affect GABA-T, were also without effect on the retinal accumulation of (3)H-GABA.4. In vitro incubation with AOAA did not increase the endogenous levels of GABA or other amino acids in the retina.5. AOAA did not significantly increase the retinal accumulation of radioactive L-glutamate, L-glutamine, taurine, glycine, alpha-aminoisobutyrate or dopamine: the accumulation of L-aspartate was increased by approximately 30%.6. The inhibition of retinal GABA-T by AOAA was time-dependent and was not reversed by pyridoxal-5'-phosphate or by repeated washing of the tissue with fresh medium.7. AOAA also inhibited glutamate decarboxylase (GAD) in retinae incubated in vitro. This inhibitory effect was partially reversed by pyridoxal-5'-phosphate.8. Efflux of radioactivity from the retina was strikingly reduced in the presence of AOAA at concentrations sufficient to inhibit GABA-T by 100%.9. These findings suggest that AOAA potentiates the accumulation of (3)H-GABA by isolated retina, not by increasing the exchange of (3)H-GABA with the endogenous GABA pools, but by reducing the metabolism of the amino acid and hence reducing the loss of radioactivity from the tissue in the form of tritiated metabolites.
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PMID:Effect of inhibitors of -aminobutyrate aminotransferase on the accumulation of 3H- -aminobutyric acid by the retina. 473 Aug 31

Dynamics of gamma-aminobutyric acid (GABA) content, the level of glutamate and total content of dicarboxylic amino acids and their amides as well as glutamate decarboxylase and GABA-alpha-ketoglutarate aminotransferase activities in the brain of F1CBAXC57BL/6 hybrid mice were determined during a year. The content of GABA and adicarboxylic acids in the brain in autumn-winter is higher than in summer. An analogous regularity is observed in the activity of basic enzymes of the GABA metabolism. Against a background of the common regularity (higher values of these indices in winter and autumn and comparatively low in summer) a particularly pronounced significant increase (as compared with the minimum level) is found in March for the activity of GABA-shunt enzymes, the content of GABA and dicarboxylic amino acids. The data obtained testify to the fact that in autumn-winter the brain tissue is characterized by a comparatively high content of dicarboxylic amino acids, their amides and GABA as well as by a more intensive functioning of the GABA-shunt, which is confirmed by the activation of the enzymes of GABA production and utilization in the corresponding seasons.
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PMID:[Seasonal changes in the gamma-aminobutyric acid system of the mouse brain]. 612 May 93

The activity of glutamate decarboxylase (L-glutamate carboxy-1-lyase; EC 4.1.1.15), GABA-transaminase (GABA-alpha-ketoglutarate aminotransferase, EC 2.6.1.19), content of gamma-aminobutyric, glutamic and aspartic acids were studied in different parts and subcellular particles of the cat and rat brain. It is shown that regional and subcellular distribution of the GABA metabolic components in the cat and rat brain are mainly similar, but quantitative indices are different.
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PMID:[Content of components GABA metabolism in the brain of cats and rats]. 612 26

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

Uptake, synthesis, storage, and release of gamma-aminobutyric acid (GABA) are some of the characteristic properties of GABA-ergic neurons. In the present study, we have used these properties as physiological probes to follow the emergence and maturation of GABA-ergic neurons during postnatal development of the rabbit retina. There is autoradiographic, immunocytochemical, and pharmacological evidence that some amacrine cells and certain neurons in the ganglion cell layer probably use GABA as the neurotransmitter. These neurons take up GABA, contain the GABA-synthesizing enzyme L-glutamic acid decarboxylase (GAD, EC 4.1.1.15), and release the accumulated GABA by a CA++-dependent mechanism when depolorized with high extracellular K+ concentration. In this study, we show that certain neurons in the newborn retina already possess a specific mechanism for GABA uptake. The positions and numbers of these cells in the developing retina suggest that they will become GABA-ergic neurons in the adult retina. These putative GABA-ergic neurons are, however, probably immature at birth because newborn retinas contain only low levels of GABA and GAD. Additionally, there is relatively little K+-stimulated, Ca++-dependent release of (3H)-GABA from the newborn retinas. GABA concentrations and GAD activities in developing retinas increase steadily postnatally, reaching about 80% of the adult levels by day 9. The activities of the GABA-degrading enzyme, GABA-glutamate transaminase (GABA-T, EC 2.6.1.19), follow a similar pattern of maturation during retinal development. K+ stimulated GABA release, however, remains low until about day 6, and then increases dramatically from 20% to 85% of the adult level over the next 3 days. Taken together, our results indicate that in the rabbit retina, the commitment by certain neurons to use GABA as the transmitter is made prenatally. These neurons are immature at birth but are biochemically, physiologically, and probably functionally mature by about 9 days after birth.
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PMID:Postnatal development of GABA-ergic neurons in the rabbit retina. 625 33

The activity of certain key enzymes involved in glutamic acid metabolism was studied in purified brain mitochondria and in mitochondrial subfractions separated in a discontinuous 1.2--1.6 mol/l sucrose gradient. Alanine aminotransferase and glutamate dehydrogenase were found to be matrix enzymes and aspartate aminotransferase to be associated with the inner mitochondrial membranes. After the purified mitochondria had been separated into 5 subfractions, aspartate aminotransferase and NAD+-dependent isocitrate dehydrogenase were found to be bound to the lighter mitochondrial subfractions settling at the 1.4--1.5 mol/l sucrose boundary while alanine aminotransferase, 4-aminobutyrate transaminase and glutamate dehydrogenase were associated with the heavier subfractions settling below 2.4 mol/l sucrose. The highest specific activity of the given enzymes was found in the subfraction settling at the 1.4--1.5 mol/l sucrose boundary, the only exception being alanine aminotransferase activity, whose maximum was found in the subfractions settling in 1.5 and 1.6 mol/l sucrose. It was concluded that alanine aminotransferase, in conjunction with glutamate dehydrogenase, is linked to NH3 binding and to the oxidation of reduced adenine nucleotides; in addition, alanine aminotransferase is presumed to have the function of transporting glutamate from the mitochondria to the extramitochondrial space.
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PMID:Alanine aminotransferase and some other enzymes in different populations of free brain cortex mitochondria. 645 52


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