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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to gain insight into the metabolic modifications induced in rat brain tissues by helium-neon (He-Ne) laser irradiation, in the research described here, we investigated the variations in the activity of the enzymes aspartate transferase (AST, EC 2.6.1.4), both cytosolic and mitochondrial, glutamate dehydrogenase (GIDH, EC 1.4.1.3), and total superoxide dismutase (SOD, EC 1.15.1.1), in the brain of rats treated with a very small dose (1.08 J) of He-Ne laser radiation. The rats were sacrificed 4 h after the treatment. The enzymes were evaluated spectrophotometrically in brain extracts of irradiated animals and also in untreated rats (controls) and rats that underwent simulated treatment (stressed). The data obtained from 5-10 animals assayed individually showed that, in the in toto brain tissues of the irradiated rats compared to the stressed rats, there was a marked increase of total SOD, together with an appreciable decrease of cytosolic AST, and insignificant variations in mitochondrial AST and GIDH. Stress alone caused a considerable decrease of total SOD and small but statistically significant increases of s-AST, m-AST, and GIDH.
Mol Chem Neuropathol 1991 Oct
PMID:Rat brain metabolism enzyme activity variations following He-Ne laser irradiation. 177 92

As the result of two mutually compensating frameshift mutations, three successive codons with third-position A were generated in the Neurospora crassa am (NADP-specific glutamate dehydrogenase: GDH) gene. These codons do not occur at all elsewhere in the gene and only infrequently in other highly expressed Neurospora genes. The double-frameshift strain produces only 25 to 35% of the normal level of GDH, whether measured as enzyme activity or as immunoprecipitable protein, but its level of GDH mRNA is normal. Although the modified enzyme is somewhat more heat-sensitive than the wild-type in vitro, its stability in vivo was found to be indistinguishable from that of the wild-type. It is concluded that the introduction of consecutive rare codons reduces the efficiency of translation of the mRNA. The possible mechanisms of such an effect are discussed.
J Mol Biol 1991 Oct 05
PMID:An apparent rare-codon effect on the rate of translation of a Neurospora gene. 183 52

Repeat-induced point mutation (RIP) has been used to generate new mutations in the previously uncharacterised gene for malate synthase in Neurospora crassa. Molecular clones carrying the am (NADP-glutamate dehydrogenase) gene and the malate synthase gene from either N. crassa or Aspergillus nidulans have been introduced into Neurospora as ectopic duplicate copies by transformation, selecting for the am+ function in a deletion host. A number of meiotic progeny derived from these transformants were unable to use acetate as sole carbon source, yielded no detectable malate synthase activity and demonstrated extensive cytosine methylation of their duplicated sequences. The new locus has been designated acu-9 and has been assigned to linkage group VII.
Mol Gen Genet 1990 Sep
PMID:Premeiotic disruption of the Neurospora crassa malate synthase gene by native and divergent DNAs. 197 42

The URE2 gene of Saccharomyces cerevisiae has been cloned and sequenced. It encodes a predicted polypeptide of 354 amino acids with a molecular weight of 40,226. Deletion of the first 63 amino acids does not have any effect on the function of the protein. Studies with disruption alleles of the URE2 and GLN3 genes showed that both genes regulate GLN1 and GDH2, the structural genes for glutamine synthetase and NAD-linked glutamate dehydrogenase, respectively, at the transcriptional level, but expression of the regulatory genes does not appear to be regulated. Active URE2 gene product was required for the inactivation of glutamine synthetase upon addition of glutamine to cells growing with glutamate as the source of nitrogen. The predicted URE2 gene product has homology to glutathione S-transferases. The gene has been mapped to chromosome XIV, 5.9 map units from petX and 3.4 map units from kex2.
Mol Cell Biol 1991 Feb
PMID:The URE2 gene product of Saccharomyces cerevisiae plays an important role in the cellular response to the nitrogen source and has homology to glutathione s-transferases. 199 Feb 86

The dissociation constant for the complex of rhodanese and Cibacron Blue, determined by analytical affinity chromatography using rhodanese immobilized on controlled-pore glass (CPG) beads (200 nm pore diameter) and aminohexyl-Cibacron Blue, was 44 microM which agreed well with the kinetic inhibition constant, suggesting that the dye binds at or near the active site of this enzyme. Formation of a binary complex of the dye and lactate dehydrogenase (LDH) was also characterized by direct chromatography of LDH on CPG/immobilized Cibacron Blue (KD = 0.29 microM). The binary complex formed between LDH and NADH was characterized by analytical affinity chromatography using both CPG/immobilized LDH and immobilized Cibacron Blue. Since the dye competes with NADH in binding to the active site of LDH, competitive elution chromatography using the immobilized dye allows determination of the dissociation constant of the soluble LDH.NADH complex. Agreement between the dissociation constants determined by direct chromatography of NADH on immobilized LDH (KD = 1.4 microM) and that determined for the soluble complex (KD = 2.4 microM) indicates that immobilization of LDH did not affect the interaction. Formation of various binary, ternary and quaternary complexes of bovine liver glutamate dehydrogenase (GDH) with glutamate, NADPH, NADH, and ADP was also investigated using immobilized GDH. This approach allows characterization of the enzyme/ligand interactions without the complicating effect of enzyme self-association. The affinity for NADPH is considerably greater in the ternary complex (including glutamate) as compared to the binary complex (0.38 microM vs 22 microM); however, occupancy of the regulatory site by ADP greatly reduces the affinity in both complexes (6.4 microM and 43 microM, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
J Mol Recognit
PMID:Characterization of specific interactions of coenzymes, regulatory nucleotides and cibacron blue with nucleotide binding domains of enzymes by analytical affinity chromatography. 209 89

We have constructed a series of deletions in the 5' non-coding sequences of the cloned Neurospora crassa am gene which specifies NADP specific glutamate dehydrogenase. All of the deletions begin at -4.4 kb with respect to the am transcription start site and extend for various distances toward the am gene. Using vectors with a truncated fragment of the am gene, we introduced these deletions into the chromosome upstream of am by transformation. Analysis of glutamate dehydrogenase expression in strains with the deletion mutations confirmed that there are two upstream regulatory sequences (URS) that control the expression of the am gene. The more distal of these elements (URSam beta) has been limited to the 157 bp between -1924 and -2081 with respect to the start of am transcription. The proximal element (URSam alpha) was limited to the 97 bp between -1296 and -1393. The DNA sequence of the entire region was determined. Within the sequences that contain the URS elements several regions of homology with yeast UAS sequences were found. Gel mobility assays with DNA fragments containing the URS elements indicated that sequences in both elements are bound by nuclear proteins from Neurospora. The interaction of these proteins and the DNA fragments was found to be specific.
Mol Gen Genet 1990 Apr
PMID:Nucleotide sequence and nuclear protein binding of the two regulatory sequences upstream of the am (GDH) gene in Neurospora. 216 25

The glutamate dehydrogenase structural gene, gdhA, was mapped at 38.6 min on the genetic map and at 1860 kb on the physical map. A detailed map of this region is presented.
Mol Gen Genet 1990 Sep
PMID:The glutamate dehydrogenase structural gene of Escherichia coli. 227 89

In the presence of Mg2+, pure glutamate dehydrogenase is more reactive with NADPH than with NADH and is markedly activated by elevations in the ADP/ATP ratio or the addition of leucine. Because these are properties of glutamate dehydrogenase in mitochondria but not properties of the pure enzyme studied in the absence of Mg2+, Mg2+ could be a ligand that confers upon glutamate dehydrogenase the regulatory properties of this enzyme found in situ. In the absence of the allosteric activators ADP, leucine, or succinyl-CoA, Mg2+ is an inhibitor and increases product inhibition by alpha-ketoglutarate in the forward reaction and substrate inhibition by alpha-ketoglutarate in the reverse reaction. However, the allosteric activators convert Mg2+ from an inhibitor into an activator of the forward reaction. In the reverse reaction, ADP also converts Mg2+ from an inhibitor into an activator and leucine eliminates inhibition by Mg2+. Because Mg2+ is an inhibitor in the absence of activator that also increases inhibition by alpha-ketoglutarate, whereas in the presence of activator Mg2+ has no effect or is itself an activator, Mg2+ magnifies the effect of the activator, and magnification increases with increases in the concentration of alpha-ketoglutarate. Leucine and its analog 2-aminobicyclo (2.2.1) heptane 2-carboxylic acid (BCH) have almost identical effects on both human and bovine glutamate dehydrogenase in both the presence and absence of Mg2+. However, advantages of BCH over leucine as a potential pharmacological activator of glutamate dehydrogenase are that BCH is not metabolized and, unlike leucine, BCH does not inhibit ornithine transcarbamylase. Isoleucine and valine alone have little effect on human glutamate dehydrogenase, but isoleucine slightly inhibits the enzyme in the presence of leucine.
Mol Pharmacol 1990 Jun
PMID:Regulation of glutamate dehydrogenase by Mg2+ and magnification of leucine activation by Mg2+. 235 6

The effect of Ca2+-homopantothenate (HOPA) treatment (250 mg/kg for 5 d) has been studied by evaluating the specific activity of enzymes related to: glycolytic pathway (hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase), tricarboxylic acid cycle (citrate synthase, malate dehydrogenase), mitochondrial electron transfer chain (succinate dehydrogenase, cytochrome oxidase), NADH redox state (NADH cytochrome c reductase), acetylcholine metabolism (acetylcholinesterase), and glutamate metabolism (glutamate dehydrogenase). The enzymatic activity assays were performed on homogenate in toto, nonsynaptic mitochondria and synaptosomes isolated from: cerebral cortex, hippocampus, striatum, hypothalamus, medulla oblongata, and cerebellum of normoxic rats and rats submitted to intermittent normobaric hypoxia (90:10, N2:O2). In normoxic rats, HOPA was unable to induce any modification. Hypoxia per se induced a decrease in the activity of synaptosomal cytochrome oxidase in cerebral cortex, hippocampus, and cerebellum.
Mol Chem Neuropathol 1989 Jun
PMID:Effect of Ca2+-homopantothenate and mild hypoxia on some enzyme activities evaluated in subcellular fractions from different rat brain regions. 254 16

Specific in vitro-generated insertion, replacement, and deletion mutations have been integrated near the chromosomal locus of am (NADP-specific glutamate dehydrogenase) of Neurospora crassa. Two approaches have been successful. One approach used am+-containing vectors capable of integrating at any site in the genome. This technique was used to introduce a specific 700 bp insertion near the am locus and to replace chromosomal sequences near am with plasmid DNA. Efficiency was low, however, and many transformants had to be screened to find the desired alterations among the ectopic insertions unless the incoming DNA had a large region of homology with the am region. A second approach increased the efficiency by using vectors containing a truncated am gene, so that prototrophs could arise only by homologous recombination. Overall transformation frequency was reduced relative to the first method, but a large fraction of the transformations involved specific alterations of the am region.
Mol Gen Genet 1989 Jun
PMID:Use of transformation to make targeted sequence alterations at the am (GDH) locus of Neurospora. 254 76


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