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The Role of Glutamate Dehydrogenase Activity in Development of Neurodegenerative Disorders  [PDF]
Matej Kravos, Ivan Male?i?
World Journal of Neuroscience (WJNS) , 2017, DOI: 10.4236/wjns.2017.71013
Abstract: The specific role of Glutamate dehydrogenase (GLDH) in the brain is not yet clear, but it is an important enzyme in protein degradation as well as a metabolism regulator of glutamate as a neurotransmitter. The enzyme probably provides crucial protection for postsynaptic membranes against the neurotoxic effects of glutamate neurotransmitters. In men, GLDH activity declines almost evenly through the ages; in women, it declines faster in the first five decades. In the years of menopause, GLDH activity declines slower. The diminished GLDH activities in leukocytes and in the brain vary considerably, but they are parallel with the progress of neurodegenerative diseases. The GLDH activity is partly deficient in the brain, particularly in the leukocytes of patients with heterogeneous neurological disorders and degeneration of multiple neuronal systems. We found a statistically significant difference of GLDH activity in the cerebrospinal fluid in patients with neurological diseases and unexpected in patients with degenerative and inflammatory disorders. The decrease in GLDH activity in the cerebrospinal fluid of patients with neurodegenerative disorders may be one of the reasons for the neuro-excito-toxic glutamate effect. Defining the GLDH activity in leukocytes is at the moment the sole experimental method. The second one could be the measurement in cerebrospinal fluid. The results suggest a possibility to regulate glutamate level in human brain through activation of GLDH.
Cloning and characterization of the glutamate dehydrogenase gene inBacillus licheniformis
Bing Zhu,Guanqiao Yu,Jiabi Zhu,Shanjiong Shen
Science China Life Sciences , 2000, DOI: 10.1007/BF02879284
Abstract: ThegdhA genes of IRC-3 GDH strain and IRC-8 GDH+ strain were cloned, and they both successfully complemented the nutritional lesion of anE. coli glutamate auxotroph, Q100 GDH . However, thegdhA gene from the mutant IRC-8 GDH+ strain failed to complement the glutamate deficiency of the wild type strain IRC-3. ThegdhA genes of the wild type and mutant origin were sequenced separately. No nucleotide difference was detected between them. Further investigations indicated that thegdhA genes were actively expressed in both the wild type and the mutant. Additionally, no GDH inhibitor was found in the wild type strain IRC-3. It is thus proposed that the inactivity of GDH in wild type is the result of the deficiency at the post-translational level of thegdhA expression. Examination of the deduced amino acid sequence ofBacillus licheniformis GDH revealed the presence of the motifs characteristic of the family I-type hexameric protein, while the GDH ofBacillus subtilis belongs to family II.
Cloning and characterization of the glutamate dehydrogenase gene in Bacillus licheniformis
ZHU Bing,YU Guanqiao,ZHU Jiabi,SHEN Shanjiong,
朱冰
,俞冠翘,朱家璧,沈善炯

中国科学C辑(英文版) , 2000,
Abstract: The gdhA genes of IRC-3 GDH strain and IRC-8 GDH strain were cloned, and they both successfully complemented the nutritional lesion of an E. coli glutamate auxotroph, Q100 GDH". However, the gdhA gene from the mutant IRC-8 GDH strain failed to complement the glutamate deficiency of the wild type strain IRC-3. The gdhA genes of the wild type and mutant origin were sequenced separately. No nucleotide difference was detected between them. Further investigations indicated that the gdhA genes were actively expressed in both the wild type and the mutant. Additionally, no GDH inhibitor was found in the wild type strain IRC-3. It is thus proposed that the inactivity of GDH in wild type is the result of the deficiency at the post-translational level of the gdhA expression. Examination of the deduced amino acid sequence of Bacillus licheniformis GDH revealed the presence of the motifs characteristic of the family I -type hexameric protein, while the GDH of Bacillus subtilis belongs to family II.
Anticonvulsant Drugs, Brain Glutamate Dehydrogenase Activity and Oxygen Consumption  [PDF]
Lourdes A. Vega Rasgado,Guillermo Ceballos Reyes,Fernando Vega-Díaz
ISRN Pharmacology , 2012, DOI: 10.5402/2012/295853
Abstract: Glutamate dehydrogenase (GDH, E.C. 1.4.1.3.) is a key enzyme for the biosynthesis and modulation of glutamate (GLU) metabolism and an indirect γ-aminobutyric acid (GABA) source, here we studied the effect of anticonvulsants such as pyridoxal phosphate (PPAL), aminooxyacetic acid (AAOA), and hydroxylamine (OHAMINE) on GDH activity in mouse brain. Moreover, since GLU is a glucogenic molecule and anoxia is a primary cause of convulsions, we explore the effect of these drugs on oxygen consumption. Experiments were performed in vitro as well as in vivo for both oxidative deamination of GLU and reductive amination of α-ketoglutarate (αK). Results in vitro showed that PPAL decreased oxidative deamination of GLU and oxygen consumption, whereas AAOA and OHAMINE inhibited GDH activity competitively and also inhibited oxygen consumption when αK reductive amination was carried out. In contrast, results showed that in vivo, all anticonvulsants enhanced GLU utilization by GDH and also decreased oxygen consumption. Together, results suggest that GDH activity has repercussions on oxygen consumption, which may indicate that the enzyme activity is highly regulated by energy requirements for metabolic activity. Besides, GDH may participate in regulation of GLU and, indirectly GABA levels, hence in neuronal excitability, becoming a key enzyme in seizures mechanism. 1. Introduction Seizures are considered to be the result of an unbalance between excitatory and inhibitory systems, and it is believed that anticonvulsants exert their actions through enhancement of inhibitory-mediated transmission, the reduction of excitatory-mediated transmission, or a combination of both [1]. Glutamate (GLU) is considered the main excitatory neurotransmitter in the central nervous system (SNC) in mammals, besides, it is the precursor for the biosynthesis of gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter. It has been proposed that GLU may be involved in the pathogenesis of seizures [2], since many pathological processes in the SNC leading to the development of convulsive syndrome can increase the activity of glutamatergic transmission as the common end pathway [3–7]. Glutamate dehydrogenase (GDH, EC 1.4.1.3.) catalyzes the reversible deamination of L-glutamate to 2-oxoglutarate. Evidences of the particular importance of GDH activity in the nervous system are GDH isolated from patients with heterogeneous neurological disorders, characterized by multisystem atrophy, displayed a marked reduction on its activity [8], with a similar trend in cortex and hippocampus of patients
Roles of cysteine residues in the inhibition of human glutamate dehydrogenase by palmitoyl-CoA  [cached]
Sung-Woo Cho
BMB Reports , 2012,
Abstract: Human glutamate dehydrogenase isozymes (hGDH1 andhGDH2) have been known to be inhibited by palmitoyl-CoAwith a high affinity. In this study, we have performed the cassettemutagenesis at six different Cys residues (Cys59, Cys93,Cys119, Cys201, Cys274, and Cys323) to identify palmitoyl-CoA binding sites within hGDH2. Four cysteine residuesat positions of C59, C93, C201, or C274 may be involved, atleast in part, in the inhibition of hGDH2 by palmitoyl-CoA.There was a biphasic relationship, depending on the levels ofpalmitoyl-CoA, between the binding of palmitoyl-CoA and theloss of enzyme activity during the inactivation process. The inhibitionof hGDH2 by palmitoyl-CoA was not affected by theallosteric inhibitor GTP. Multiple mutagenesis studies on thehGDH2 are in progress to identify the amino acid residuesfully responsible for the inhibition by palmitoyl-CoA.
Using the RNA synthetic activity of glutamate dehydrogenase to illuminate the natural role of the enzyme  [PDF]
Godson O. Osuji, Wenceslaus C. Madu
Advances in Biological Chemistry (ABC) , 2012, DOI: 10.4236/abc.2012.24047
Abstract: Glutamate Dehydrogenase (GDH; EC 1.4.1.2) catalyzes the reversible amination of α-ketoglutarate to glutamate, and the polymerization of nucleoside triphosphate(s) to RNA. But the natural role of the reversible amination reaction is the subject of an expanding conversation. The aim was to illuminate the natural role of GDH through its RNA synthetic activity. Stoichiometric combinations of mineral salts that targeted the GDH subunit compositions were applied to field-cultivated peanuts. GDH of seeds were made to synthesize RNA in the deamination and then in the amination direction. Free amino acids were analyzed by HPLC. Glutamate synthase (GOGAT) was assayed by photometry. Free amino acid yields in-creased from the control’s lowest (9.8 kg·ha–1) and amination-deamination ratio (0.05) through 12.0 - 23.0 kg·ha–1 in the K-, N+K+P+S-, Pi-, N+S-, S-treated peanuts with amination-deamination ratios between 0.6 and 10.0 until at the P+K-treated peanut which had the highest amino acid yield (52.4 kg·ha–1) and the highest amination-deamination ratio (61). The Km and Vmax values of GOGAT were within the normal range. Yields of free amino acids resulting from GDH aminating activity increased from <1.0 kg·ha–1 in the control, through 2.2 in the N+S-, 6.84 in the P+N-, 17.3 in the N-, to 42.6 kg·ha–1 in the P+K- treated peanut. These results show that the natural role of the GDH amination activity is to assimilate escalating multiples of the quantities of NH4+ ion as assimilated via the GS-GOGAT pathway. Peanut protein yields increased in parallel with GDH aminating activities and free amino acid yields such that the control peanut had the lowest protein (<26.0 kg·ha–1) and the yields increased exponentially (500 - 600 kg·ha–1) through the K-, P+S-, Pi-, N-treated to 910 kg·ha–1 in the P+K-treated peanut with the highest aminating activity of GDH. The ability of GDH aminating activity to escalate protein yields of food crops could be employed to address proteinenergy malnutrition syndrome of developing nations.
The Role of Glutamine Oxoglutarate Aminotransferase and Glutamate Dehydrogenase in Nitrogen Metabolism in Mycobacterium bovis BCG  [PDF]
Albertus J. Viljoen, Catriona J. Kirsten, Bienyameen Baker, Paul D. van Helden, Ian J. F. Wiid
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0084452
Abstract: Recent evidence suggests that the regulation of intracellular glutamate levels could play an important role in the ability of pathogenic slow-growing mycobacteria to grow in vivo. However, little is known about the in vitro requirement for the enzymes which catalyse glutamate production and degradation in the slow-growing mycobacteria, namely; glutamine oxoglutarate aminotransferase (GOGAT) and glutamate dehydrogenase (GDH), respectively. We report that allelic replacement of the Mycobacterium bovis BCG gltBD-operon encoding for the large (gltB) and small (gltD) subunits of GOGAT with a hygromycin resistance cassette resulted in glutamate auxotrophy and that deletion of the GDH encoding-gene (gdh) led to a marked growth deficiency in the presence of L-glutamate as a sole nitrogen source as well as reduction in growth when cultured in an excess of L-asparagine.
Molecular Characterization of the Iranian Isolates of Giardia Lamblia: Application of the Glutamate Dehydrogenase Gene
Z Babaei,H Oormazdi,L Akhlaghi,S Rezaie
Iranian Journal of Public Health , 2008,
Abstract: Background: This study was conducted to determine of molecular epidemiology of the Giardia lamblia by PCR-RFLP method in Tehran, capital of Iran. Methods: Thirty eight stool samples were randomly selected from 125 patients diagnosed with giardiasis using microscopy in Tehran. DNA extraction of some samples were performed by phenol/chloroform/isoamyl alcohol method and to raise the sensitivity of the PCR assay, the genomic DNA of the others were extracted using glass beads and the QIAamp Stool Mini Kit in order to effectively remove the PCR inhibitors. A single step PCR-RFLP assay, targeting the glutamate dehydrogenase (gdh) locus, was used to differentiate within and between assemblages A and B that have been found in humans. Results: Of the 38 isolates, 33 samples (87%) were found as G. lamblia (genotype AII), 3 (7.8%) belonged to assemblage B, genotype BIII, the mixed of genotype AII and B were detected only in two samples (5.2%). Conclusions: PCR-RFLP is a sensitive and powerful analytical tool that allows effective genotype discrimination within and between assemblages at targeting gdh gene, and makes it possible to identify the presence of mixed genotypes. Our data suggest that there is an anthroponotic origin of the infection route, assemblage A group II, in Tehran so it seems that the main reservoir of Giardia infection is humans in the area studies.
Structural Properties of the RNA Synthesized by Glutamate Dehydrogenase for the Degradation of Total RNA  [PDF]
Godson O. Osuji, Paul M. Johnson
Advances in Enzyme Research (AER) , 2018, DOI: 10.4236/aer.2018.63004
Abstract: Glutamate dehydrogenase (GDH)-synthesized RNA, a nongenetic code-based RNA is suitable for unraveling the structural constraints imposed on the regulation (transcription, translation, siRNA etc.) of metabolism by genetic code. GDH-synthesized RNAs have been induced in whole plants to knock out target mRNA populations thereby producing plant phenotypes that are allergen-free; enriched in fatty acids, essential amino acids, shikimic acid, resveratrol etc. Methods applied hereunder for investigating the structural properties of GDH-synthesized RNA included purification of GDH isoenzymes, synthesis of RNA by the isoenzymes, reverse transcription of the RNA to cDNA, sequencing of the cDNA, computation of the G+C-contents, profiling the stability through PCR amplification compared with genetic code-based DNA; and biochemical characterization of the RNAs synthesized by individual hexameric isoenzymes of GDH. Single product bands resulted from the PCR amplification of the cDNAs of GDH-synthesized RNA, whereas several bands resulted from the amplification of genetic code-based DNA. The cDNAs have wide G+C-contents (35% to 59%), whereas genetic code-based DNA has narrower G+C-contents (50% to 60%). The GDH β6 homo-hexameric isoenzyme synthesized the A+U-rich RNAs, whereas the a6, and α6 homo-hexameric isoenzymes synthesized the G+C-rich RNAs. Therefore, the RNA synthesized by GDH is different from genetic code-based RNAs. In vitro chemical reactions revealed that GDH-synthesized RNA degraded total RNA to lower molecular weight products. Therefore, GDH-synthesized RNA is RNA enzyme. Dismantling of the structural constraints imposed on RNA by genetic code liberated RNA to become an enzyme with specificity to degrade unwanted transcripts. The RNA enzyme activity of GDH-synthesized RNA is ubiquitous in cells; it is readily induced by treatment of plants with mineral nutrients etc. and may simplify experimental approaches in plant enzymology and molecular biology research projects.
Metabolite Fingerprinting in Transgenic Nicotiana tabacum Altered by the Escherichia coli Glutamate Dehydrogenase Gene
R. Mungur,A. D. M. Glass,D. B. Goodenow,D. A. Lightfoot
Journal of Biomedicine and Biotechnology , 2005, DOI: 10.1155/jbb.2005.198
Abstract: With about 200 000 phytochemicals in existence, identifying those of biomedical significance is a mammoth task. In the postgenomic era, relating metabolite fingerprints, abundances, and profiles to genotype is also a large task. Ion analysis using Fourier transformed ion cyclotron resonance mass spectrometry (FT-ICR-MS) may provide a high-throughput approach to measure genotype dependency of the inferred metabolome if reproducible techniques can be established. Ion profile inferred metabolite fingerprints are coproducts. We used FT-ICR-MS-derived ion analysis to examine gdhA (glutamate dehydrogenase (GDH; EC 1.4.1.1)) transgenic Nicotiana tabacum (tobacco) carrying out altered glutamate, amino acid, and carbon metabolisms, that fundamentally alter plant productivity. Cause and effect between gdhA expression, glutamate metabolism, and plant phenotypes was analyzed by 13NH4
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