Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.6.1.19 (GABA transaminase)
 808 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutamate decarboxylase, gamma-aminobutyrate-alpha-ketoglutarate aminotransferase and NAD-linked and NADP-linked succinic semialdehyde dehydrogenase, all constituting the GABA (gamma-aminobutyrate)-shunt pathway of glutamate metabolism are localized in the mitochondrial matrix in a streptomycin-bleached mutant of Euglena gracilis strain Z. Glutamate dehydrogenase, requiring NADP as the cofactor, was distributed in the cytoplasm. An improved version of the controlled digestion method for preparing Euglena mitochondria, which involves use of trypsin and a trypsin inhibitor and removal of broken cells before mechanical disruption of cells, is also described.
 ...
PMID:Subcellular localization of the GABA-shunt enzymes in Euglena gracilis strain Z. 11 50

We have isolated mutants of Escherichia coli K-12 CS101B that have lost the ability to utilize gamma-aminobutyrate as a source of nitrogen. One class of mutants, which were not affected in the utilization of other nitrogen sources (proline, arginine, glycine), included many isolates with lesions in gamma-aminobutyrate transport or in its transamination and one mutant completely devoid of succinic semialdehyde dehydrogenase activity and exhibiting low gamma-aminobutyrate transport and transamination. gamma-Aminobutyrate-utilizing revertants of the latter recovered full transport and transamination capacities but remained dehydrogenaseless. Another class of mutants showed pleiotropic defects in nitrogen metabolism. One such mutant was lacking glutamate synthase activity. The genes specifying the synthesis of gamma-aminobutyrate permease, gabP, gamma-aminobutyrate transaminase, gabT, and succinic semialdehyde dehydrogenase, gabD, and the control gene, gabC, that coordinately regulates their expression all form a cluster on the E. coli chromosome, linked to the srl and recA loci (at 57.5 min). The mutations with pleiotropic effects on the metabolism of nitrogenous compounds are not linked to the gab cluster.
 ...
PMID:Isolation and properties of Escherichia coli K-12 mutants impaired in the utilization of gamma-aminobutyrate. 37 39

It is hypothesized that buffers capable of forming a Schiff base with the PLP of gamma-aminobutyric acid aminotransferase (GABA-AT) may lead to denaturation and inactivation of the enzyme. On the basis of this hypothesis three new methods for the selective destruction of GABA-AT in GABAse (a commercial bacterial source of a mixture of GABA-AT and succinic semialdehyde dehydrogenase [SSDH]) and from pig brain are described: (1) dialysis against a primary or secondary amine buffer; (2) gel filtration with a primary or secondary amine buffer as eluent; (3) inactivation with gabaculine followed by dialysis or gel filtration with pyrophosphate buffer. The SSDH activity in GABAse, which remains unchanged by all of these methods, may then be used in a coupled assay to measure the activity of GABA-AT from different sources. These results also suggest that the use of primary and secondary amine buffers should be avoided when inhibitors are being tested with GABA-AT.
 ...
PMID:Inactivation of gamma-aminobutyric acid aminotransferase by various amine buffers. 128 56

The gabCTDP gene cluster, which specifies and regulates synthesis of the gamma-aminobutyrate (GABA) transport carrier, of glutamate-succinic semialdehyde transaminase, and of succinic semialdehyde dehydrogenase, responsible for the uptake and metabolism of gamma-aminobutyric acid in Escherichia coli K-12, was cloned in vivo, using the mini-Mu replicon bacteriophage Mu dI5086 as the vector. A subclone containing a 7.8-kilobase (kb) EcoRI-HindIII fragment complemented all of our Gab- mutants. By restriction mapping, this DNA fragment was located at kb 2800.5 to 2808.5 on the physical map of the E. coli K-12 chromosome. A subclone containing a 1.8-kb EcoRI-SalI fragment complemented the gab-repressed strain CS101A (wild-type gabC) but did not complement any gab structural gene mutants. The gab genes are divergently transcribed from promoters located in the vicinity of the unique BamHI site. Transcription in both directions is under dual control of catabolite repression and nitrogen regulation. Using a procaryotic DNA-directed translation system, we observed three insert-coded polypeptide bands of 53 to 55, 45 to 48, and 40 to 43 kilodaltons (kDa). In vivo studies with subcloned fragments of the gab DNA identified the 53- to 55- and 45- to 48-kDa bands as products of the BamHI-SalI fragment and the 40- to 43-kDa band as the product of the EcoRI-SalI fragment. An additional 26- to 28-kDa band was identified as the product of the BamHI-HindIII fragment. Furthermore, the BamHI-SalI fragment was shown to specify synthesis of the two GABA enzymes, whereas synthesis of the GABA carrier was specified by the BamHI-HindIII fragment. No catalytic function in addition to its regulatory role could be attributed to the EcoRI-SalI gene product.
 ...
PMID:In vivo cloning and characterization of the gabCTDP gene cluster of Escherichia coli K-12. 218 54

We have characterized two genes of the Escherichia coli K-12 gab cluster, which encodes the enzymes of the 4-aminobutyrate degradation pathway. The nucleotide sequence of gabT, coding for glutamate:succinic semialdehyde transaminase (EC 2.6.1.19), alternatively known as 4-aminobutyrate transaminase, was determined. The structural gene consists of 1,281 nucleotides specifying a protein of 426 amino acids with a molecular mass of 45.76 kDa. The protein shows significant homologies to the ornithine transaminases from Saccharomyces cerevisiae and from rat and human mitochondria. Three functionally and structurally important amino acid residues of the transaminase were identified by sequence comparison studies, and evolutionary relationships of the aminotransferases are discussed. The gabD gene, encoding succinic semialdehyde dehydrogenase (EC 1.2.1.16), was cloned and shown to be located adjacent to the 5' end of gabT. Expression studies with subfragments of the initially cloned DNA region revealed a maximal size of 1.7 kb for gabD. Both genes are cotranscribed from a promoter located upstream of gabD.
 ...
PMID:Molecular analysis of two genes of the Escherichia coli gab cluster: nucleotide sequence of the glutamate:succinic semialdehyde transaminase gene (gabT) and characterization of the succinic semialdehyde dehydrogenase gene (gabD). 225 72

The tetrazolium salt procedure of van Gelder (1965) for the demonstration of GABA transaminase (GABAT; the most important GABA degrading enzyme) was adapted for microphotometric measurements of GABAT activities in brain sections using the hippocampus of rats as selected brain region. The final incubation medium consisted of 50 mM GABA, 5 mM alpha-ketoglutarate, 7 mM NAD, 10 mM sodium azide, 6 mM nitroblue tetrazolium chloride, 20 mM malonate and 15% polyvinyl alcohol in 0.05 M Hepes buffer; the final pH was 8.0. There was a linear relationship between GABAT activity and section thickness up to 14 microns and between GABAT activity and reaction time at least up to 20 min (kinetic and end-point measurements). Phenazine methosulfate as an exogenous electron carrier and pyridoxal-5-phosphate as coenzyme of GABAT did not enhance the demonstrable GABAT activities, whereas sodium azide as a blocker of the respiratory chain resulted in an increase of demonstrable enzyme activities. A coreaction of succinate dehydrogenase was excluded by the use of malonate (competitive inhibitor). Using the incubation medium described GABAT activities were demonstrated via the endogenous enzymes succinic semialdehyde dehydrogenase and NADH tetrazolium reductase which were shown to be not rate limiting and seems to be similarly localized as GABAT.
 ...
PMID:Microphotometric determination of enzymes in brain sections. II. GABA transaminase. 233 51

Pyritinol, a vitamin B6 derivative considered to have an activating effect on brain inhibited glutamate decarboxylase in concentrations of 0.05-1.0 mmol/l. This effect was not dependent on the pyridoxal-5'-phosphate concentration. An increase in the glutamate level reduced the inhibitory effect of pyritinol, but inhibition was not competitive. It is supposed that this modification of inhibition of glutamate decarboxylase by the substrate concentration might be associated with the presence of two glutamate decarboxylases with different affinities for the substrate. The inhibitory effect of pyritinol was dependent on integrity of the disulphide bond in the pyritinol molecule. Inhibition of glutamate decarboxylase increased in correlation to time--possibly in association with progressive oxidation of the SH-groups of the enzyme. Pyritinol did not influence GABA transaminase activity, but lessened the oxidation of GABA to carbon dioxide. It is assumed that succinic semialdehyde dehydrogenase activity was inhibited.
 ...
PMID:Pyritinol and the enzymes of gamma-aminobutyric acid (GABA) synthesis and degradation. 297 3

We have documented the presence of five mitochondrial enzymes in samples of chorionic villus tissue and measured the levels of activity. Three of the enzymes catalyse biotin-dependent reactions. These are propionyl-CoA carboxylase, 3-methylcrotonyl-CoA carboxylase and pyruvate carboxylase. The other enzymes, 4-aminobutyric acid aminotransferase and succinic semialdehyde dehydrogenase, are involved in the degradation of the central inhibitory neurotransmitter GABA. Distinct diseases in which there is deficiency of each of these enzymes have been documented in man. Significant levels of activity were observed for all five enzymes in chorionic villus tissue. This methodology should permit early prenatal diagnosis of deficiencies of these enzymes by chorionic villus biopsy in the first trimester.
 ...
PMID:Activity of biotin-dependent and GABA metabolizing enzymes in chorionic villus samples: potential for 1st trimester prenatal diagnosis. 372 38

The use of a monoclonal-antibody immunoaffinity column for the rapid isolation of 4-aminobutyrate aminotransferases (EC 2.6.1.19) from rabbit brain and liver is described. Homogeneous enzyme protein is eluted from the immunoadsorbent with 100mM-citrate buffer, pH5, and remains stable at 4 degrees C for several days. One such column (bed volume 8 ml) has been used 40 times in a 9-month period to isolate 10-15 units of enzyme activity (specific activity approx. 3.5-7.5 units/mg) per extraction. Kinetic and spectral analysis of the enzymes from the two tissues revealed a close similarity. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis showed the isolated enzyme to have a monomeric Mr of 52 000, and this was confirmed by h.p.l.c. gel exclusion at pH 5.0. The results of Sephadex G-100 chromatography at different pH values are taken to indicate that the enzyme behaves as a dimer at pH 7.0 and above, but as a monomer at pH 5.0. 4-Aminobutyrate aminotransferase isolated from the brain by the procedure of Fowler & John [(1981) Biochem. J. 197, 149-152] is more stable than the immunoaffinity-purified material, and has been shown to contain a contaminant protein of Mr 84 000 that exhibits succinic semialdehyde dehydrogenase activity.
 ...
PMID:Purification and properties of rabbit brain and liver 4-aminobutyrate aminotransferases isolated by monoclonal-antibody immunoadsorbent chromatography. 390 9

The presence and distribution of gamma-aminobutyric acid (GABA) degradative enzyme (GABA transaminase-succinic semialdehyde dehydrogenase) activity in the rat myenteric plexus was determined histochemically using laminar preparations of the small intestine. Blue-diformazan staining resulting from reduction of the tetrazolium salt, Nitro-BT, during GABA catabolism was present in a scattered population of ileal and jejunal myenteric ganglion cells, including those resembling multipolar type II and unipolar nerve cells. Such staining was almost completely prevented under conditions of GABA-T inhibition. These results indicate that GABA is enzymically degraded at specific sites in the rat enteric nervous system where it is proposed to have a neurotransmitter function.
 ...
PMID:The distribution of GABA-transaminase-dehydrogenase activity in the myenteric plexus of rat small intestine: a histochemical analysis. 396 Mar 92


1 2 3 4 5 6 Next >>