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)

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

The control mutation that results in a concomitant severalfold 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), leading to the acquisition of the ability to utilize gamma-aminobutyrate (GABA) as the sole source of nitrogen by Escherichia coli K-12 mutants, was mapped by mating and transduction with P1kc. The locus affected, gabC, is approximately 48% co-transduced with the thyA gene, located at min 55 of the E. coli K-12 chromosome. The structural gene of the first enzyme in the GABA pathway, GSST, was mapped by interrupted mating, using one of the GSST-less mutants, DB742, isolated in this work. The mutated locus, gabT, is situated at about min 73 of the E. coli chromosome, close to the gltC gene. Genetic evidence concerning the sensitivity of the enzymes of the GABA pathway to catabolite repression under different physiological conditions suggests that the two structural genes of the GABA regulon do not constitute one operon.
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PMID:Genetic analysis of the gamma-aminobutyrate utilization pathway in Escherichia coli K-12. 459 Apr 73

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

The hypothesis that the brain GABA level increase which is induced by a sodium dipropyl acetate treatment arises either through inhibition of succinic semialdehyde dehydrogenase (SSADH), or through inhibition of GABA transaminase by succinic semialdehyde (SSA), has been considered. It appeared that in vivo brain GABA level increase cannot be attributed to SSADH inhibition, and that SSA is not a GABA precursor. It has been shown that SSA is neither in vivo nor in vitro a GABA-transaminase inhibitor. 4-hydroxybenzaldehyde, a potent SSADH inhibitor did not increase GABA level at a dosage which induces a 99% inhibition of SSADH.
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PMID:[Mechanism of action of an anticonvulsant, sodium dipropylacetate]. 645 31

Physical interactions between the enzymes involved in the catabolism of the neurotransmitter 4-aminobutyrate were detected by means of affinity chromatography and fluorescence techniques. By immobilizing one enzyme (4-aminobutyrate aminotransferase) indirectly through antibodies bound to protein A-Sepharose, it was possible to demonstrate that succinic semialdehyde dehydrogenase interacts with the aminotransferase at neutral pH and ionic strength values higher than 0.2. Increasing the ionic strength of the medium results in dissociation of the "enzyme cluster." Binding of succinic semialdehyde dehydrogenase to the aminotransferase tagged with a fluorescent probe was detected by polarization of fluorescence measurements at neutral pH. Upon saturation of the aminotransferase with succinic semialdehyde dehydrogenase, the polarization of fluorescence increases from 0.13 to 0.21. The results are consistent with a model in which one molecule of succinic semialdehyde dehydrogenase is bound to one molecule of 4-aminobutyrate aminotransferase with an equilibrium dissociation constant of 0.1 microM. Since the concentrations of both enzymes in the mitochondrial matrix have been estimated to be around 2 microM, the results obtained with the purified mitochondrial enzymes strongly suggest that the aminotransferase is saturated with succinic semialdehyde dehydrogenase to form a stable enzymatic complex under in vivo conditions.
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PMID:Interactions between 4-aminobutyrate aminotransferase and succinic semialdehyde dehydrogenase, two mitochondrial enzymes. 647 7

Succinic semialdehyde dehydrogenase deficiency has been demonstrated in a fourth patient with 4-hydroxybutyric aciduria. Lysates of freshly isolated lymphocytes and cultured lymphoblasts of the patient had much lower than control activity in the conversion of U-14C-4-aminobutyric acid to 14C-succinic acid in an assay designed to estimate succinic semialdehyde dehydrogenase utilizing endogenous 4-aminobutyrate transaminase. Lymphocyte and lymphoblast lysates of the patient accumulated U-14C-succinic semialdehyde when incubated with U-14C-4-aminobutyric acid and NAD+ whereas none could be detected in controls. Assays using U-14C-succinic semialdehyde as substrate for succinic semialdehyde dehydrogenase in lysates of cultured lymphoblasts characterized the patient as having a severe deficiency of succinic semialdehyde dehydrogenase. The data indicate that defective activity of succinic semialdehyde dehydrogenase is responsible for 4-hydroxybutyric aciduria.
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PMID:Defective succinic semialdehyde dehydrogenase activity in 4-hydroxybutyric aciduria. 648 77

The influence of neonatal beta-estradiol treatment on the development of GABA-degradative enzymes (GABA transaminase and succinic semialdehyde dehydrogenase) within rat cerebellar cortex has been studied using a semiquantitative histochemical technique. Both enzymatic activities were stimulated following beta-estradiol treatment. In particular, the granule and Purkinje cells were the most influenced cerebellar components. The findings seem to suggest that granule and Purkinje cells may represent the principal target of the cerebellar cortex for sex hormones.
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PMID:Stimulatory effect of beta-estradiol treatment on GABA-degradative enzymes within rat cerebellar cortex. 663 52

Alteration of metabolism of taurine in prolonged light- and dark-adapted frog retinae were studied in comparison with that of gamma-aminobutyric acid (GABA) and the following results were obtained. (1) Statistically significant alterations in retinal taurine, an increase in dark-adapted, and a decrease in light-adapted states, respectively, occurred when frogs were adapted continuously to light or dark for more than 3 weeks. Under the same experimental conditions, no alteration in retinal GABA was noted. (2) At 3 weeks and thereafter, a significant increase of retinal cysteine sulfinic acid decarboxylase (CSD; EC 4.1.1.12) activity, an enzyme involved in the biosynthetic pathway of taurine, also occurred in the dark, whereas the activity in the light-adapted retina was reduced. On the other hand, the retinal activity of L-glutamate decarboxylase (GAD; EC 1.1.1.15), the rate-limiting enzyme of GABA biosynthesis, was not altered in dark- as well as light-adapted state. Similarly, retinal GABA-transaminase (GABA-T; EC 2.6.1.19)-succinic semialdehyde dehydrogenase (SSADH; EC 1.2.1.16) was unaltered. (3) These alterations in retinal taurine were, however, unaccompanied by any changes in factors related to transmitter actions such as evoked release, high affinity uptake, and specific binding to synaptic membranes. The above results suggest that, different from GABA as a potent candidate for inhibitory neurotransmitter, retinal taurine may act as neuromodulator and/or may play an important role as a basic factor for maintaining cellular integrity under certain pathophysiological conditions.
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PMID:Alteration of metabolism of retinal taurine following prolonged light and dark adaptation: a quantitative comparison with gamma-aminobutyric acid (GABA). 697 81

We have determined the nucleotide sequences of two structural genes of the Escherichia coli gab cluster, which encodes the enzymes of the 4-aminobutyrate degradation pathway: gabD, coding for succinic semialdehyde dehydrogenase (SSDH, EC 1.2.1.16) and gabP, coding for the 4-aminobutyrate (GABA) transport carrier (GABA permease). We have previously reported the nucleotide sequence of the third structural gene of the cluster, gabT, coding for glutamate: succinic semialdehyde transaminase (EC 2.6.1.19). All three gab genes are transcribed unidirectionally and their orientation within the cluster is 5'-gabD-gabT-gabP-3'. gabT and gabP are separated by an intergenic region of 234-bp, which contains three repetitive extragenic palindromic (REP) sequences. The gabD gene consists of 1,449 nucleotides specifying a protein of 482 amino acids with a molecular mass of 51.7 kDa. The protein shows significant homologies to the NAD(+)-dependent aldehyde dehydrogenase (EC 1.2.1.3) from Aspergillus nidulans and several mammals, and to the tumor associated NADP(+)-dependent aldehyde dehydrogenase (EC 1.2.1.4) from rat. The permease gene gabP comprises 1,401 nucleotides coding a highly hydrophobic protein of 466 amino acids with a molecular mass of 51.1 kDa. The GABA permease shows features typical for an integral membrane protein and is highly homologous to the aromatic acid carrier from E. coli, the proline, arginine and histidine permeases from Saccharomyces cerevisiae and the proline transport protein from A. nidulans. Uptake of GABA was increased ca. 5-fold in transformants of E. coli containing gabP plasmids.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Molecular organization of the Escherichia coli gab cluster: nucleotide sequence of the structural genes gabD and gabP and expression of the GABA permease gene. 829 11

The composition and properties of the tricarboxylic acid cycle of the microaerophilic human pathogen Helicobacter pylori were investigated in situ and in cell extracts using [1H]- and [13C]-NMR spectroscopy and spectrophotometry. NMR spectroscopy assays enabled highly specific measurements of some enzyme activities, previously not possible using spectrophotometry, in in situ studies with H. pylori, thus providing the first accurate picture of the complete tricarboxylic acid cycle of the bacterium. The presence, cellular location and kinetic parameters of citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate oxidase, fumarate reductase, fumarase, malate dehydrogenase, and malate synthase activities in H. pylori are described. The absence of other enzyme activities of the cycle, including alpha-ketoglutarate dehydrogenase, succinyl-CoA synthetase, and succinate dehydrogenase also are shown. The H. pylori tricarboxylic acid cycle appears to be a noncyclic, branched pathway, characteristic of anaerobic metabolism, directed towards the production of succinate in the reductive dicarboxylic acid branch and alpha-ketoglutarate in the oxidative tricarboxylic acid branch. Both branches were metabolically linked by the presence of alpha-ketoglutarate oxidase activity. Under the growth conditions employed, H. pylori did not possess an operational glyoxylate bypass, owing to the absence of isocitrate lyase activity; nor a gamma-aminobutyrate shunt, owing to the absence of both gamma-aminobutyrate transaminase and succinic semialdehyde dehydrogenase activities. The catalytic and regulatory properties of the H. pylori tricarboxylic acid cycle enzymes are discussed by comparing their amino acid sequences with those of other, more extensively studied enzymes.
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PMID:The tricarboxylic acid cycle of Helicobacter pylori. 1009 6


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