• BMB Reports
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• 제34권3호
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• pp.268-273
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• 2001

In addition to the recognition site for glutamate, the N-methyl-D-aspartate (NMDA)-preferring glutamate receptor subtype shows a binding site for glycine. In this paper, we present the effects of 3-(4,6-dichloro-2-carboxymethylamino-5,7-dichloroquinoline-2-carboxylic acid (MDL 29951), a potent inhibitor of glycine binding to the NMDA receptor, on glutamate dehydrogenase (GDH) from bovine brains. The incubation of GDH isoproteins from bovine brains with MDL 29951 resulted in a dose-dependent loss of enzyme activity Separately or together, 2-oxoglutarate and NADH did not give an efficient protection against the inhibition, indicating that GDH isoproteins saturated with NADH or 2-oxoglutarate are still open to attack by MDL 29951. MDL 29951 was an uncompetitive inhibitor with respect to both 2-oxoglutarate and NADH for GDH isoproteins. These results suggest that the binding site of MDL 29951 is not directly located at the catalytic site, and the inhibition of GDH isoproteins by MDL 29951 is probably due to a steric hindrance, or a conformational change altered upon the interaction of the enzyme with its inhibitor. The inhibitory effects of MDL 29951 on GDH isoproteins were significantly diminished in the presence of ADP. GDH I reacted more sensitively with ADP than GDH II on the inhibition by MDL 29951. Our results suggest a possibility that the two types of GDHs are differently regulated by MDL 29951, depending on the physiological concentrations of ADP.

• BMB Reports
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• 제32권5호
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• pp.515-520
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• 1999

Incubation of two types of glutamate dehydrogenase isoproteins from bovine brain with the arginine-specific dicarbonyl reagent phenylglyoxal resulted in a biphasic loss of enzyme activity. Reaction of the glutamate dehydrogenase isoproteins with phenylglyoxal caused a rapid loss of 53~62% of the enzyme activities and modification of two residues of arginine per enzyme subunit. Prolonged incubation of the glutamate dehydrogenase isoproteins with phenylglyoxal resulted in the modification of an additional four residues of arginine per enzyme subunit without further loss of the residual activities. Partial protection against inactivation was provided by the coenzyme NADH or substrate 2-oxoglutarate. The most marked decrease in the rate of inactivation was observed by the combined addition of NADH and 2-oxoglutarate, suggesting that the first two modified arginine residues are in the vicinity of the catalytic site. However, inactivation of the glutamate dehydrogenase isoproteins by phenylglyoxal appears to be partial with approximately 40% activity remained after an extended reaction time with excess reagent, suggesting that the modified arginine residues may not be directly involved in catalysis. The lack of complete protection by substrates also suggest the possibility that the modified arginine residues are not directly involved at the active site, and the partial loss of activity by the modification of arginine residues may be due to a conformational change. There were no significant differences between the two glutamate dehydrogenase isoproteins in sensitivities to inactivation by phenylglyoxal, indicating that the microenvironmental structures of the glutamate dehydrogenase isoproteins are very similar to each other.

• BMB Reports
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• 제30권5호
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• pp.332-336
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• 1997

The stimulatory effects of leucine on the activities of two soluble forms of brain glutamate dehydrogenase isoproteins (GDH I and GDH II) have been studied at various conditions. There were significant differences between GDH I and GDH II in their sensitivities to the action of leucine. When the effects of varied leucine concentrations on GDH activities were studied in the direction of reductive amination of 2-oxoglutarate with NADPH as a coenzyme, a marked activation was observed for both isoproteins at leucine concentrations up to 10 mM, whereas both isoproteins showed activation to a lesser extent with NADH as a coenzyme. The stimulatory effects of leucine on GDH activities in the direction of the oxidative deamination of glutamate were also observed, but to a much lesser extent. Leucine relieved the inhibition of GDH I by GTP and this resulted in an increase in the apparent activation by leucine in the presence of GTP. 2-Oxoglutarate was found to give rise to high substrate inhibition and leucine significantly reduced the substrate inhibition in the presence of $200\;{\mu}M$ NADH. Thus, the effects of leucine might be composed of a direct effect on the enzyme together with a relief of high substrate inhibition.

• Journal of Plant Biology
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• 제16권1_2호
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• pp.6-11
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• 1973

The utilization of acetate by Dunaliella tertiolecta was examined, and the detections and assays of the enzymes of the tricarboxylic acid cycle and the glyoxylate pathway were described. Acetate could not be utilized as a sole carbon source for the growth. The carboxyl carbon of acetate was incorporated more rapidly into CO2 than the methyl carbon. It was identified that malate, succinate, citrate and etc., were accumulated whne [U-14C] acetate was supplied to the cell free homogenate. The following enzyme activities were measured; acetothiokinase, isocitrate dehydrogenase, fumarase, malate dehydrogenase and aconitase. Though isocitratase, malate synthetase, succinate dehydrogenase and oxoglutarate dehydrogenase could not be detected, 14C from succinate was easily contributed to CO2 and cell component. The evidence suggested that the glyoxylate pathway was not operative and showed that the TCA cycle was the all important pathway in the oxidation of acetate to CO2 in Dunaliella.

• BMB Reports
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• 제45권2호
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• pp.91-95
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• 2012

Glutamate dehydrogenase from axenic bacterial cultures of a new microorganism, called GWE1, isolated from the interior of a sterilization drying oven, was purified by anion-exchange and molecular-exclusion liquid chromatography. The apparent molecular mass of the native enzyme was 250.5 kDa and was shown to be an hexamer with similar subunits of molecular mass 40.5 kDa. For glutamate oxidation, the enzyme showed an optimal pH and temperature of 8.0 and $70^{\circ}C$, respectively. In contrast to other glutamate dehydrogenases isolated from bacteria, the enzyme isolated in this study can use both $NAD^+$ and $NADP^+$ as electron acceptors, displaying more affinity for $NADP^+$ than for $NAD^+$. No activity was detected with NADH or NADPH, 2-oxoglutarate and ammonia. The enzyme was exceptionally thermostable, maintaining more than 70% of activity after incubating at $100^{\circ}C$ for more than five hours suggesting being one of the most thermoestable enzymes reported in the family of dehydrogenases.

• Journal of Ginseng Research
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• 제48권2호
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• pp.236-244
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• 2024

Background: Fusarium oxysporum (F. oxysporum) is the primary pathogenic fungus that causes Panax notoginseng (P. notoginseng) root rot disease. To control the disease, safe and efficient antifungal pesticides must currently be developed. Methods: In this study, we prepared and characterized a nanoemulsion of Foeniculum vulgare essential oil (Ne-FvEO) using ultrasonic technology and evaluated its stability. Traditional Foeniculum vulgare essential oil (T-FvEO) was prepared simultaneously with 1/1000 Tween-80 and 20/1000 dimethyl sulfoxide (DMSO). The effects and inhibitory mechanism of Ne-FvEO and T-FvEO in F. oxysporum were investigated through combined transcriptome and metabolome analyses. Results: Results showed that the minimum inhibitory concentration (MIC) of Ne-FvEO decreased from 3.65 mg/mL to 0.35 mg/mL, and its bioavailability increased by 10-fold. The results of gas chromatography/mass spectrometry (GC/MS) showed that T-FvEO did not contain a high content of estragole compared to Foeniculum vulgare essential oil (FvEO) and Ne-FvEO. Combined metabolome and transcriptome analysis showed that both emulsions inhibited the growth and development of F. oxysporum through the synthesis of the cell wall and cell membrane, energy metabolism, and genetic information of F. oxysporum mycelium. Ne-FvEO also inhibited the expression of 2-oxoglutarate dehydrogenase and isocitrate dehydrogenase and reduced the content of 2-oxoglutarate, which inhibited the germination of spores. Conclusion: Our findings suggest that Ne-FvEO effectively inhibited the growth of F. oxysporum in P. notoginseng in vivo. The findings contribute to our comprehension of the antifungal mechanism of essential oils (EOs) and lay the groundwork for the creation of plant-derived antifungal medicines.

• Journal of Applied Biological Chemistry
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• 제42권1호
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• pp.1-6
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• 1999

Poly-${\beta}$-hydroxybutyrate (PHB) and enzymes related PHB metabolism have been measured in nitrogen-fixing symbiosis of chickpea and cowpea plants. Bacteroids from chickpea and cowpea contained PHB to 0.8% and 43% of their dry weight, respectively, whereas the free-living cells CC 1192 and I 16 produced $285{\pm}55mg$ and $157{\pm}18mg$ of PHB g (dry weight)$^{-1}$. To further understand why chickpea bacteroids contained little PHB, the enzyme activities of PHB metabolism (3-ketothiolase, acetoacetyl-CoA reductase, PHB depolymerase, and 3-hydroxybutyrate dehydrogenase), the TCA cycle (malate dehydrogenase, citrate synthase, and isocitrate dehydrogenase), and related reactions (malic enzyme, pyruvate dehydrogenase, and glutamate:2-oxoglutarate transaminase) were compared in extracts from chickpea and cowpea bacteroids and the respective free-living bacteria. Significant differences were observed between chickpea and cowpea bacteroids and between the bacteroid and free-living forms of CC 1192, with respect to the capacity for some of these reactions. It is indicated that a greater potential for oxidizing malate to oxaloacetate in chickpea bacteroids could be a factor that favors the utilization of acetyl-CoA in TCA cycle rather than for PHB synthesis.

• BMB Reports
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• 제40권6호
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• pp.1077-1082
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• 2007

Human glutamate dehydrogenase exists in hGDH1 (housekeeping isozyme) and in hGDH2 (nerve-specific isozyme), which differ markedly in their allosteric regulation. In the nervous system, GDH is enriched in astrocytes and is important for recycling glutamate, a major excitatory neurotransmitter during neurotransmission. Chloroquine has been known to be a potent inhibitor of house-keeping GDH1 in permeabilized liver and kidneycortex of rabbit. However, the effects of chloroquine on nerve-specific GDH2 have not been reported yet. In the present study, we have investigated the effects of chloroquine on hGDH2 at various conditions and showed that chloroquine could inhibit the activity of hGDH2 at dose-dependent manner. Studies of the chloroquine inhibition on enzyme activity revealed that hGDH2 was relatively less sensitive to chloroquine inhibition than house-keeping hGDH1. Incubation of hGDH2 was uncompetitive with respect of NADH and non-competitive with respect of 2-oxoglutarate. The inhibitory effect of chloroquine on hGDH2 was abolished, although in part, by the presence of ADP and L-leucine, whereas GTP did not change the sensitivity to chloroquine inhibition. Our results show a possibility that chloroquine may be used in regulating GDH activity and subsequently glutamate concentration in the central nervous system.

• Journal of Microbiology
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• 제42권3호
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• pp.216-222
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• 2004

In a previous paper, the ogdH gene that encodes 2-oxoglutarat dehydrogenase was isolated from Salmonella typhimurium. The catalytic N-terminal region in the enzyme was found to be very specific for the Salmonella species. Therefore, the aim of the present study was to detect S. typhimurium in food sources using primers designed for OGDH-l and OGDH-2 which were based on the salmonella-specific region of the ogdH gene. A simple polymerase chain reaction (PCR) detection method was developed to detect low numbers of S. typhimurium in a chicken meat microbial consortium. Using the ogdH-specific primers under stringent amplification conditions and for gene probe analysis, fewer than 100 colony-forming units (CFUs) were detectable when pure cultures were employed. When the PCR assay was run on S. typhimurium-contaminated meat contents, only the positive meat samples containing as few as 200 CFUs reacted to the assay. The method employed for sample processing is simple and it was determined to provide a sensitive means of detecting trace amounts of S. typhimurium-specific sequences in the presence of mixed meat microbial populations. When compared with six representative intestinal gram-negative bacterial strains in foods, including Vibrio parahaemolyticus, V. vulnificus, Enterobacter cloacae, E. coli O157:H7, Pseudomonas aeruginosa, and Proteus sp., S. typhimurium had a unique and distinct PCR product (796 bp). In conclusion, the two OGDH primers were found to be rapid and sensitive detectors of Salmonella spp for the PCR method.

• Journal of Microbiology
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• 제44권3호
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• pp.301-310
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• 2006

Two pathways of ammonium assimilation and glutamate biosynthesis have been identified in microorganisms. One pathway involves the NADP-linked glutamate dehydrogenase, which catalyzes the amination of 2-oxoglutarate to form glutamate. An alternative pathway involves the combined activities of glutamine synthetase, which aminates glutamate to form glutamine, and glutamate synthase, which transfers the amide group of glutamine to 2-oxoglutarate to yield two molecules of glutamate. We have cloned the large subunit of the glutamate synthase (GOGAT) from Salmonella typhimurium by screening the expression of GOGAT and complementing the gene in E. coli GOGAT large subunit-deficient mutants. Three positive clones (named pUC19C12, pUC19C13 and pUC19C15) contained identical Sau3AI fragments, as determined by restriction mapping and Southern hybridization, and expressed GOGAT efficiently and constitutively using its own promoter in the heterologous host. The coding region expressed in Escherichia coli was about 170 kDa on SDS-PAGE. This gene spans 4,732 bases, contains an open reading frame of 4,458 nucleotides, and encodes a mature protein of 1,486 amino acid residues (Mr =166,208). The EMN-binding domain of GOGAT contains 12 glycine residues, and the 3Fe-4S cluster has 3 cysteine residues. The comparison of the translated amino acid sequence of the Salmonella GOGAT with sequences from other bacteria such as Escherichia coli, Salmonella enterica, Shigella flexneri, Yersinia pestis, Vibrio vulnificus and Pseudomonas aeruginosa shows sequence identity between 87 and 95%.