Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A two-step method for assaying creatinine in serum and urine samples, suitable with automated analyzers, is reported. Reagent 1, for the first step, contains a blanking system [creatine amidinohydrolase (CRTase), urease, glutamate dehydrogenase, NADPH, and 2-oxoglutarate] and a NADPH-regenerating system [Mg(2+)-dependent isocitrate dehydrogenase (ICD), MgCl2, and excess isocitrate]. Reagent 2, for the second step, contains the metal-chelating reagent trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CyDTA) and a trigger system [creatinine amidohydrolase (CRNase)]. When a specimen is mixed with reagent 1, all the creatine, urea, and NH3 present are removed by the blanking and NADPH systems. On adding reagent 2, CyDTA inactivates ICD to inhibit the NADPH system. Simultaneously, the creatinine (1 mol) in the specimen is hydrolyzed into creatine by CRNase, and then releases NADP+ (2 mol) through the blanking system. Our optimized method can determine creatinine linearly up to 500 mg/L, with within-day CVs < 1.2% and day-to-day CVs < 2.7%.
 ...
PMID:Enzymatic rate assay of creatinine in serum and urine. 840 98

In Klebsiella aerogenes, the formation of a large number of enzymes responds to the quality and quantity of the nitrogen source provided in the growth medium, and this regulation requires the action of the nitrogen regulatory (NTR) system in every case known. Nitrogen regulation of several operons requires not only the NTR system, but also NAC, the product of the nac gene, raising the question of whether the role of NAC is to activate operons directly or by modifying the specificity of the NTR system. We isolated an insertion of the transposon Tn5tac1 which puts nac gene expression under the control of the IPTG-inducible tac promoter rather than the nitrogen-responsive nac promoter. When IPTG was present, cells carrying the tac-nac fusion activated NAC-dependent operons and repressed NAC-repressible operons independent of the nitrogen supply and even in the absence of an active NTR system. Thus, NAC is sufficient to regulate operons like hut (encoding histidase) and gdh (encoding glutamate dehydrogenase), confirming the model that the NTR system activates nac expression and NAC activates hut and represses gdh. Activation of urease formation occurred at a lower level of NAC than that required for glutamate dehydrogenase repression, and activation of histidase formation required still more NAC.
 ...
PMID:The product of the Klebsiella aerogenes nac (nitrogen assimilation control) gene is sufficient for activation of the hut operons and repression of the gdh operon. 845 54

A gram-negative bacterium which was capable of oxidizing reduced inorganic sulfur compounds was isolated from agricultural soil and designated BI-42. This new isolate grew on a wide range of organic substrates but was not able to grow autotrophically and lacked ribulose 1,5-bisphosphate carboxylase, a key enzyme of carbon dioxide fixation. These results suggested that strain BI-42 was a chemolithoheterotroph. Ammonia and nitrate were not used as sole nitrogen sources for growth, and strain BI-42 lacked glutamate synthase activity, which resulted in glutamate auxotrophy. The glutamate dehydrogenase activity of this organism was apparently insufficient for ammonia assimilation. On the basis of the results of additional biochemical tests, the G + C content of the DNA, the results of a respiratory ubiquinone analysis, the results of a 16S ribosomal DNA sequence analysis, the fatty acid composition, and the results of a membrane lipid analysis, strain BI-42 was identified as a phylogenetically and physiologically distinct taxon belonging to the alpha subclass of the Proteobacteria. Bosea thiooxidans gen. nov., sp. nov. is the name proposed for this taxon.
 ...
PMID:Oxidation of thiosulfate by a new bacterium, Bosea thiooxidans (strain BI-42) gen. nov., sp. nov.: analysis of phylogeny based on chemotaxonomy and 16S ribosomal DNA sequencing. 886 27

We developed a new simple assay for potassium ion in serum using urea amidolyase (UAL) from yeast sp. The method is based on activation of the enzyme by potassium ion. We eliminated endogenous ammonium ion by use of glutamate dehydrogenase (GLDH), and then monitored the production of ammonium ion by UAL, urea, ATP, bicarbonate and magnesium ions. Ammonium ion was produced proportional to the potassium ion concentration and was determined by adding GLDH to produce NADP+ in the presence of 2-oxoglutarate and NADPH. We monitored the change of absorbance at 340 nm. The inhibitory effect of calcium ion to this assay was eliminated by adding glycoletherdiamine-N, N, N', N'-tetraacetic acid to the reaction. The within-assay coefficients of variation (CV) of this method were 0.9-1.55% (n = 10) at 3.32-6.18 mmol/L. Day-to-day CVs ranged from 1.49% to 2.46%. The analytical recovery was 96-108%. The correlation coefficient between the values obtained by our method (y) and those by the ion-selective electrode (ISE) method (x) was 0.994 (y = 1.032x-0.166 mmol/L, Syx = 0.110, n = 100). The presence of bilirubin, haemoglobin or other ions did not affect this assay, confirming the usefulness of this assay for clinical purposes.
 ...
PMID:New enzymatic assay with urea amidolyase for determining potassium in serum. 924 70

A novel flow-injection (FIA) system, for the rapid and direct determination of both total ammonia (T[NH3]) and total carbon dioxide (T[CO2]) in clinical blood samples, has been developed. Samples were injected into a carrier stream of H2O, then emerged with a reagent stream, where the analyte was converted into a gaseous species and diffused across a PTFE gas-permeable membrane into an acceptor stream. The trapped NH3/CO2 in the acceptor was determined on line by a bulk acoustic wave (BAW) impedance sensor. At a through-put of 20 and 65 h(-1), the proposed system exhibited a linear frequency response up to 200 micromol l(-1) ammonium and 20 mmol l(-1) bicarbonate with a detection limit of 1.0 and 10 micromol l(-1), respectively. Results obtained for T(NH3) in serum and T(CO2) in plasma were in agreement with those obtained by the conventional glutamate dehydrogenase (GDH) method and gas-sensing electrode method, respectively. The effects of composition of acceptor stream, cell constant of conductivity electrode, sample volume, flow rate and potential interferents on the FIA signals were also discussed.
 ...
PMID:Flow-injection determination of total ammonia and total carbon dioxide in blood based on gas-diffusion separation and with a bulk acoustic wave impedance sensor. 953 87

The hyperthermophilic bacterium Thermotoga maritima, which grows at up to 90 degrees C, contains an L-glutamate dehydrogenase (GDH). Activity of this enzyme could be detected in T. maritima crude extracts, and appeared to be associated with a 47-kDa protein which cross-reacted with antibodies against purified GDH from the hyperthermophilic archaeon Pyrococcus woesei. The single-copy T. maritima gdh gene was cloned by complementation in a glutamate auxotrophic Escherichia coli strain. The nucleotide sequence of the gdh gene predicts a 416-residue protein with a calculated molecular weight of 45,852. The gdh gene was inserted in an expression vector and expressed in E. coli as an active enzyme. The T. maritima GDH was purified to homogeneity. The NH2-terminal sequence of the purified enzyme was PEKSLYEMAVEQ, which is identical to positions 2-13 of the peptide sequence derived from the gdh gene. The purified native enzyme has a size of 265 kDa and a subunit size of 47kDa, indicating that GDH is a homohexamer. Maximum activity of the enzyme was measured at 75 degrees C and the pH optima are 8.3 and 8.8 for the anabolic and catabolic reaction, respectively. The enzyme was found to be very stable at 80 degrees C, but appeared to lose activity quickly at higher temperatures. The T. maritima GDH shows the highest rate of activity with NADH (Vmax of 172 U/mg protein), but also utilizes NADPH (Vmax of 12 U/mg protein). Sequence comparisons showed that the T. maritima GDH is a member of the family II of hexameric GDHs which includes all the GDHs isolated so far from hyperthermophiles. Remarkably, phylogenetic analysis positions all these hyperthermophilic GDHs in the middle of the GDH family II tree, with the bacterial T. maritima GDH located between that of halophilic and thermophilic euryarchaeota.
 ...
PMID:Glutamate dehydrogenase from the hyperthermophilic bacterium Thermotoga maritima: molecular characterization and phylogenetic implications. 968 Mar 36

Ammonia transport and glutamine synthesis were studied in the hyperammonaemic rat brain in vivo using 15N-NMR spectroscopy at a plasma ammonia level of approximately 0.39 mM raised via an intravenous [15N]-ammonium acetate infusion. The initial slope of the time course of the summed cerebral 15N-labelled metabolites was used to determine the rate of ammonia net transport during hyperammonemia as 0.13 +/- 0.02 micromol/min/g (mean +/- SD; n = 5). Based on the total accumulation of glutamine and the 1:2 stoichiometric relationship between fluxes of four-carbon skeletons and nitrogen atoms, the rate of de novo glutamine synthesis through anaplerosis and subsequent glutamate dehydrogenase action was calculated to be 0.065 +/- 0.01 micromol/min/g. The rate of total glutamine synthesis was estimated to be 0.20 +/- 0.06 micromol/min/g (n = 5) by fitting the [5-15N]glutamine time course to a previously described model of glutamate-glutamine cycling between astrocytes and neurones. A large dilution was also observed in [2-15N]glutamine, which supports the glutamate-glutamine cycle as being an important pathway for neuronal glutamate repletion in vivo.
 ...
PMID:15N-NMR spectroscopy studies of ammonia transport and glutamine synthesis in the hyperammonemic rat brain. 977 82

Ammonia levels in various tissues of the marble goby Oxyeleotris marmoratus remained constant throughout a 72 h period of air exposure. The rate of ammonia excretion in these experimental fish decreased to approximately one-fifth of that of the submerged control. Ammonia was not converted to urea during air exposure because there were no significant increases in urea content in the tissues. Also, urea excretion rate was lowered to one-fiftieth that of the submerged fish. After 24 h of air exposure, there was a significant increase in muscle glutamine content, which peaked at 48 h. The increase in glutamine content could account for the decreases in the amounts of ammonia and urea excretion during air exposure. The specific activities of hepatic glutamate dehydrogenase (amination) and glutamine synthetase in these experimental fish increased threefold and thirtyfold, respectively, in comparison with the submerged controls. Thus, O. marmoratus appears to be the first known teleost that responds to air exposure by activating hepatic glutamine synthetase to detoxify internally produced ammonia.
 ...
PMID:The marble goby oxyeleotris marmoratus activates hepatic glutamine synthetase and detoxifies ammonia to glutamine during air exposure 988 36

Carbon paste wax electrodes incorporating thermophilic L-glutamate dehydrogenase, NADP and a polymeric toluidine blue O (poly-TBO) mediator have been characterised for the amperometric determination of L-glutamate at 313-318 K in a flow injection analysis (FIA) system. The biosensors exhibit good sensitivity, mechanical stability and reproducibilty, unlike carbon paste- or carbon wax-based electrodes under the same conditions. The carbon paste wax electrode responds linearly to L-glutamate up to 40 mM, the detection limit is 0.3 mM and the RSD (n = 10) for 5 mM L-glutamate was 7.6%. The response to some potential interferents has been quantified. Addition of finely ground hexaammineruthenium (III) trichloride ([Ru(NH3)6]Cl3) to the carbon paste wax electrodes decreases the FIA peak width and increases the peak current. The metal complex appears to accelerate the rate of oxidation of NAD(P)H by poly-TBO.
 ...
PMID:Characterisation of a thermophilic L-glutamate dehydrogenase biosensor for amperometric determination of L-glutamate by flow injection analysis. 1010 39

NAD+ facilitates high-yield reactivation of clostridial glutamate dehydrogenase (GDH) after unfolding in urea. The specificity of this effect has been explored by using analogues and fragments of NAD+. The adenine portion, unlike the nicotinamide portion, is important for reactivation. Alteration in the nicotinamide portion, in acetylpyridine adenine dinucleotide, has little effect, whereas loss of the 6-NH2 substitution on the adenine ring, in 6-deamino NAD, diminishes the effectiveness of the nucleotide in promoting refolding. Also ADP-ribose, lacking nicotinamide, promotes reactivation whereas NMN-phosphoribose, lacking the adenine, does not. Of the smaller fragments, those containing an adenosine moiety, and especially those with one or more phosphate groups, impede the refolding ability of NAD+, and are able to bind to the folding intermediate though unable to facilitate refolding. These results are interpreted in terms of the known 3D structure for clostridial glutamate dehydrogenase. It is assumed that the refolding intermediate has a more or less fully formed NAD+-binding domain but a partially disordered substrate-binding domain and linking region. Binding of NAD+ or ADP-ribose appears to impose new structural constraints that result in completion of the correct folding of the second domain, allowing association of enzyme molecules to form the native hexamer.
 ...
PMID:Specificity of coenzyme analogues and fragments in promoting or impeding the refolding of clostridial glutamate dehydrogenase. 1021 32


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>