Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.4.1.2 (glutamate dehydrogenase)
4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The occurrence and levels of activity of various enzymes of carbohydrate catabolism in culture forms (promastigotes) of 4 human species of Leishmania (L. brasiliensis, L. donovani, L. mexicana, and L. tropica) were compared. These organisms possess enzymes of the Embden-Meyerhof pathway but lack lactate dehydrogenase. No evidence could be found for the production of lactic acid by growing cultures and lactic acid could not be detected either in cell-free preparations or after incubation of cell-free extracts with pyruvate and NADH under appropriate conditions. All 4 species possess alpha-glycerophosphate dehydrogenase and alpha-glycerophosphate phosphatase which together could regenerate NAD, thus compensating for the absence of lactate dehydrogenase. The oxidative and nonoxidative reactions of the hexose monophosphate pathway are present in all 4 species. Cell-free extracts have pyruvate dehydrogenase activity which allows the entry of pyruvate into and its subsequent oxidation through the tricarboxylic acid cycle. All enzymes of this cycle, including a thiamine pyrophosphate dependent alpha-ketoglutarate dehydrogenase, are present. Both NAD and NADP-linked malate dehydrogenase activities are present. The isocitrate dehydrogenase is NADP specific. There is an active glutamate dehydrogenase which could compete with alpha-ketoglutarate dehydrogenase for the common substrate (alpha-ketoglutarate). Replenishment of C4 acids is accomplished by heterotrophic CO2 fixation catalyzed by pyruvate carboxylase. All 4 species have high levels of NADH oxidase activity. Several enzymes thus far not found in any species of Leishmania have been demonstrated. These are: phosphoglucose isomerase, triose phosphate isomerase, fructose-1, 6-diphosphatase, 3-phosphoglycerate kinase, enolase, alpha-glycerophosphate dehydrogenase, alpha-glycerophosphate phosphatase, pyruvate dehydrogenase complex, citrate synthase, aconitase, alpha-ketoglutarate dehydrogenase, glutamate dehydrogenase, and NADH oxidase.
...
PMID:Enzymes of carbohydrate metabolism in four human species of Leishmania: a comparative survey. 100 46

An enzymatic, fluorometric method is described for determination of serum urea on silicone-rubber pads. In this method, the reagents are lyophilized on the surface of the pads, NADH on one side and a mixture of urease, glutamate dehydrogenase, and alpha-ketoglutarate on the other. The rate of disappearance of NADH fluorescence at 460nm (excitation wavelength, 340 nm) is monitored and related to serum urea concentration. The calibration curve is linear to 250 mg of urea per liter. The method affords a rapid, simple, and inexpensive means for urea assay, the results of which correlate well with automatic diacetyl monoxime method (correlation coefficient, 0.998).
...
PMID:Enzymatic determination of serum urea on the surface of silicone-rubber pads. 111 80

Sources of variation in assays of aspartate aminotransferase (EC 2.6.1.1) activity were examined in an interlaboratory survey and through an examination of materials used as calibration materials in these assays. Four highly stable lyophilized specimens containing human cytoplasmic enzyme, with activities of 0, 22, 46, and 96 U/liter at 30 degrees C and optimal substrate concentrations, were assayed by 319 laboratories. Mean values obtained on these specimens by laboratories using 2,4-dinitrophenylhydrazine kits varied among manufacturers and deviated from values expected from this procedure. The average coefficient of variation (CV) with these kits was greater than 20%. Automated continuous-flow procedures with use of diazonium salt showed the best precision (av CV, less than 10%). However, the automated continuous-flow malate dehydrogenase/NADH coupled method produced an average CV greater than 20%. Results from each of the automated methods were related to a reference malate dehydrogenase/NADH coupled continuous kinetic assay method by temperature relationships alone. Mean values from manual diazonium salt procedures were 1.7-fold greater than similar reference values (av CV was 18%). The higher results were attributed to the use of poorly-defined units and to an artifact caused by chromophore stabilizers in this procedure when aqueous samples are used. The average CV in continuous kinetic methods varied among kit manufacturers, ranging from 6 to 28% for the specimen of highest activity. Variations in results were much larger at 366 nm than at 340 nm than at 340ity. Variations in results were much larger at 366 nm than at 340 nm. Interassay relationships of these methods are presented. Concentrations of pyruvate in commercially available calibration materials differed between manufacturers, varied in stability, and deviated from the expected concentration. For some colorimetric assays the precision attained on reported absorbance values for the enzyme specimens was of the same order of magnitude as that for pyruvate standards. Other sources of error are revealed by the interlaboratory survey. The value of commercially available sources of enzyme activity as calibration or control materials was assessed by evaluating the following properties: activity at suboptimal concentrations of L-aspartate or 2-oxoglutarate, temperature effects, preincubation lability owing to aspartate and phosphate, pyridoxal phosphate saturation, contamination with glutamate dehydrogenase, and manufacturer's rated activity. These properties are compared to those of human cytoplasmic enzyme in a human serum matrix.
...
PMID:Interlaboratory proficiency, intermethod comparison, and calibrator suitability in assay of serum aspartate aminotransferase activity. 113 21

A new adenosine analog, 3'-p-fluorosulfonyl-benzoyladenosine (3'-FSBA), has been synthesized which reacts covalently with bovine liver glutamate dehydrogenase. Native glutamate dehydrogenase is activated by ADP and inhibited by high concentrations of DPNH. Both of these effects are irreversibly decreased upon incubation of the enzyme with the adenosine analog, 3'-p-fluorosulfonyl-benzoyladenosine (3'-FSBA), while the intrinsic enzymatic activity as measured in the absence of regulatory compounds remains unaltered. A plot of the rate constant for modification as a function of the 3'-FSBA concentration is not linear, suggesting that the adenosine derivative binds to the enzyme (Ki equals 1.0 times 10-4 M) prior to the irreversible modification. Protection against modification by 3'-FSBA is provided by ADP and by high concentrations of DPNH, but not by the inhibitor GTP, the substrate alpha-keto glutarate, the coenzyme TPNH, or low concentrations of the coenzyme DPNH. The isolated altered enzyme contains approximately 1 mol of sulfonylbenzoyladenosine per peptide chain, indicating that a single specific regulatory site has reacted with 3'-tfsba. the modified enzyme exhibits normal Michaelis constants for its substrates and is still inhibited by GTP, albeit at a higher concentration, but it is not inhibited by high concentrations of DPNH. Although ADP does not appreciably activate the modified enzyme, it does (as in the case of the native enzyme) overcome the inhibition of the modified enzyme by GTP. These results suggest that ADP can bind to the modified enzyme, but that its ability to activate is affected indirectly by the modification of the adjacent tdpnh inhibitory site. It is proposed that the regulatory sites for ADP and DPNH are partially overlapping and that 3'FSBA functions as a specific affinity label for the DPNH inhibitory site of glutamate dehydrogenase. It is anticipated that 3'-p-fluorosulfonylbenzolyadenosine may act as an affinity label of other dehydrogenases as well as of other classes of enzymes which use adenine nucleotides as substrates or regulators.
...
PMID:Affinity labeling of a regulatory site of bovine liver glutamate dehydrogenase. 116 88

Mitochondria used in the present study were isolated from skeletal muscle of normal and thyroidectomized rats. The preparations were controlled by electron microscopy. It was not possible to find any morphological change induced by thyroidectomy, nevertheless, some difference appeared in the cytochrome contents which were slightly decreased. Oxygen consumption rates of thyroidectomized rat mitochondria were decreased when the particles were maintained in states 3 and 4 in the presence of various substrates, but the P/O ratios were not modified. The activities of mitochondrial enzymes were in general slightly affected by thyroidectomy except for glycerol-1-phosphate cytochrome c reductase and NADH rotenone sensitive cytochrome c reductase which were decreased and for glutamate dehydrogenase activity which was increased. The tRNA nucleotidyltransferase activity found in the mitochondrial matrix was not influenced by the absence of thyroid secretion. Normal rat muscle mitochondria incorporate 14C-leucine with an artificial ATP-generating system or with a respiratory substrate. The amino acid incorporation was decreased by thyroidectomy. Muscle mitochondria analyzed by polyacrylamide gel electrophoresis contained more than 30 protein components with MW ranging from 10.000 to 135.000. Thyroidectomy lowered the amount of a fraction of about 54.000 MW. It is not impossible that all the data observed in the absence of thyroid secretion are in relation with changes induced in the mitochondrial genome as previously shown in mitochondria isolated from liver or thyroidectomized rats.
...
PMID:[Effects of thyroidectomy of the rat on the structure and functions of skeletal muscle mitochondria]. 120 23

A new guanosine nucleotide has been synthesized and characterized: guanosine 5'-O-[S-(3-bromo-2-oxopropyl)]thiophosphate (GMPSBOP), with a reactive functional group which can be placed at a position equivalent to the pyrophosphate region of GTP. This new analog is negatively charged at neutral pH and is similar in size to GTP. GMPSBOP has been shown to react with bovine liver glutamate dehydrogenase with an incorporation of 2 mol of reagent/mol of subunit. The modification reaction desensitizes the enzyme to inhibition by GTP, activation by ADP, and inhibition by high concentrations of NADH, but does not affect the catalytic activity of the enzyme. The rate constant for reaction of GMPSBOP with the enzyme exhibits a nonlinear dependence on reagent concentration with KD = 75 microM. The addition to the reaction mixture of alpha-ketoglutarate, GTP, ADP, or NADH alone results in little decrease in the rate constant, but the combined addition of 5 mM NADH with 0.4 mM GTP or with 10 mM alpha-ketoglutarate reduces the reaction rate approximately 6-fold. GMPSBOP modifies peptides containing Met-169 and Tyr-262, of which Tyr-262 is not critical for the decreased sensitivity of the enzyme toward allosteric ligands. The presence of 0.4 mM GTP plus 5 mM NADH protects the enzyme against reaction at both Met-169 and Tyr-262, but yields enzyme with 1 mol of reagent incorporated/mol of subunit which is modified at an alternate site, Met-469. In the presence of 0.2 mM GTP + 0.1 mM NADH, protection against modification of Tyr-262, but only partial protection against labeling of Met-169, is observed. In contrast, the presence of 10 mM alpha-ketoglutarate + 5 mM NADH protect only against reaction with Met-169. The results suggest that GMPSBOP reacts at the GTP-dependent NADH regulatory site [Lark, R. H., & Colman, R. F. (1986) J. Biol. Chem. 261, 10659-10666] of bovine liver glutamate dehydrogenase, which markedly affects the sensitivity of the enzyme to GTP inhibition. The reaction of GMPSBOP with Met-169 is primarily responsible for the altered allosteric properties of the enzyme.
...
PMID:Guanosine 5'-O-[S-(3-bromo-2-oxopropyl)]thiophosphate: a new reactive purine nucleotide analog labeling Met-169 and Tyr-262 in bovine liver glutamate dehydrogenase. 132 52

Response characteristics are presented for a dual-enzyme fiber-optic biosensor for glutamate. An enzyme layer composed of glutamate dehydrogenase (GDH) and glutamate-pyruvate transaminase (GPT) is used to produce reduced nicotinamide adenine dinucleotide (NADH) at the tip of a fiber-optic probe. NADH luminescence is monitored through this probe and the measured fluorescence intensity is related to the concentration of glutamate. GDH catalyzes the formation of NADH, and GPT drives the GDH reaction by removing a reaction product and regenerating glutamate. Optimal response is obtained in a pH 7.4 Tris-HCl buffer maintained at 25 degrees C in the presence of 4 mM NAD+ and 10 mM L-alanine. The temperature profile reveals a strong negative temperature effect which is attributed to the temperature dependency of NADH luminescence. Under optimal conditions, the sensor sensitivity is 0.127 nA/microM over the 1-10 microM concentration range, the detection limit is 0.13 microM, and response times range from 4 to 8 min. The sensor response is stable for 12 days when stored at 4 degrees C. Selectivity for glutamate is excellent over most of the common amino acids as well as ascorbic acid, uric acid, taurine, and GABA. Only slight responses were observed for glutamine and lysine. The effect of ammonia on the glutamate response was found to be minimal at total ammonia nitrogen concentrations as high as 200 microM.
...
PMID:Dual-enzyme fiber-optic biosensor for glutamate based on reduced nicotinamide adenine dinucleotide luminescence. 135 Apr 33

Characteristics of the three major ammonia assimilatory enzymes, glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutamate synthase (GO-GAT) in Corynebacterium callunae (NCIB 10338) were examined. The GDH of C. callunae specifically required NADPH and NADP+ as coenzymes in the amination and deamination reactions, respectively. This enzyme showed a marked specificity for alpha-ketoglutarate and glutamate as substrates. The optimum pH was 7.2 for NADPH-GDH activity (amination) and 9.0 for NADP(+)-GDH activity (deamination). The results showed that NADPH-GDH and NADP(+)-GDH activities were controlled primarily by product inhibition and that the feedback effectors alanine and valine played a minor role in the control of NADPH-GDH activity. The transferase activity of GS was dependent on Mn+2 while the biosynthetic activity of the enzyme was dependent on Mg2+ as essential activators. The pH optima for transferase and biosynthetic activities were 8.0 and 7.0, respectively. In the transfer reaction, the Km values were 15.2 mM for glutamine, 1.46 mM for hydroxylamine, 3.5 x 10(-3) mM for ADP and 1.03 mM for arsenate. Feedback inhibition by alanine, glycine and serine was also found to play an important role in controlling GS activity. In addition, the enzyme activity was sensitive to ATP. The transferase activity of the enzyme was responsive to ionic strength as well as the specific monovalent cation present. GOGAT of C. callunae utilized either NADPH or NADH as coenzymes, although the latter was less effective. The enzyme specifically required alpha-ketoglutarate and glutamine as substrates.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Some properties of glutamate dehydrogenase, glutamine synthetase and glutamate synthase from Corynebacterium callunae. 135 47

The catalytic activity, expressed as Km and Vmax values, of 16 enzymes of practical interest with the macromolecular coenzymes poly(ethylene glycol)-N6-(2-aminoethyl)-NAD+ and poly(ethylene glycol)-N6-(2-aminoethyl)-NADP+ and their low molecular weight precursors N6-(2-aminoethyl)-NAD+ and N6-(2-aminoethyl)-NADP+, was investigated. The enzymes examined are of direct interest for organic synthesis (i.e. alcohol dehydrogenase from yeast, horse liver, or Thermoanaerobium brockii, lactic dehydrogenase, and several hydroxysteroid dehydrogenases) or are used for the regeneration of NAD+, NADP+, NADH, or NADPH (i.e. glutamate dehydrogenase from liver or Proteus, formate dehydrogenase, glucose dehydrogenase, and malic enzyme). The cycling efficiency of poly(ethylene glycol)-N6-(2-aminoethyl)-NADP+ was examined with coupled-enzymes or coupled-substrates systems. Poly(ethylene glycol)-N6-(2-aminoethyl)-NAD+ and, even more so, poly(ethylene glycol)-N6-(2-aminoethyl)-NADP+ were excellent coenzymes with several dehydrogenases. In addition, the coenzymatic properties of N6-(3-sulfonatopropyl)-NAD+, an NAD+ derivative carrying a strong anionic group, were compared with those of the newly synthesized N6-(2-hydroxy-3-trimethylammonium propyl)-NAD+, an NAD+ derivative carrying a strong cationic group. It was expected that the presence of the sulfonic or quaternary ammonium group would enhance the residence time of the coenzyme inside continuous-flow reactors if membranes with anionic or cationic groups, respectively, were used.
...
PMID:Coenzymatic properties of low molecular-weight and macromolecular N6-derivatives of NAD+ and NADP+ with dehydrogenases of interest for organic synthesis. 136 82

The determination of ammonia in plasma, using glutamate dehydrogenase, is complicated by non-specific oxidation of the coenzyme, promoted by components of the sample matrix. Measurements performed with appropriate plasma blanks show that 2'-phosphorylated coenzymes (NADPH, deamino-NADPH) are much less oxidized than NADH. By adding lactate dehydrogenase, NADH oxidation by endogenous pyruvate can be completed within a short time. Considerable consumption of coenzyme occurs, however, and endogenous L-alanine aminotransferase also represents a possible source of interference. The results of ammonia determinations using deamino-NADPH (y) or NADPH (x) were identical (a = 0.0 mumol/l, b = 1.00; r = 0.996, n = 62). With NADH as the coenzyme, the method displays adequate specificity only at high sample dilution, e.g. in the measurement of urea after conversion to ammonia.
...
PMID:Which is the appropriate coenzyme for the measurement of ammonia with glutamate dehydrogenase? 145 16


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

---