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

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Query: EC:1.4.3.11 (glutamate dehydrogenase)
4,437 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. At a physiological concentration of glutamine (0.5 mM), 87% of the total transport across the plasma membrane of liver cells isolated from fed rats involved the Na(+)-dependent system N; this was substantially inhibited by L-histidine. The residual Na(+)-independent component was attributed to system L on the basis of inhibition by 2-amino-2-norbornanecarboxylate and L-tryptophan. 2. Catabolism of glutamine by intact liver cells or by isolated mitochondria was inhibited by glutamate gamma-hydrazide with IC50 values of 13.7 +/- 3.5 microM and 22.6 +/- 3.8 microM respectively and a maximal inhibition of approx. 75%. The site of inhibition was identified as glutaminase; glutamate gamma-hydrazide inhibited this enzyme in cell-free extracts (IC50 37.8 +/- 7.7 microM) but had no activity against glutamate dehydrogenase or transport of glutamine, whether across mitochondrial or plasma membranes. 3. The major control site in cells from fed animals incubated with 0.5 mM L-glutamine was glutaminase (flux control coefficient 0.96). Appreciable control also resided in both plasma membrane transport systems, with coefficients of 0.51 for system N and -0.46 for system L, such that both interacted to provide a fine control of the intracellular concentration of the amino acid. Similar values were obtained by computer simulation based on theoretical determination of elasticities. 4. Previous controversy about the locus of regulation of hepatic glutamine metabolism is resolved by this distribution of control.
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PMID:A quantitative analysis of the control of glutamine catabolism in rat liver cells. Use of selective inhibitors. 824 Feb 66

To date, no attempt has been made to study alterations occurring in the amino acid profile in chronic models of thioacetamide-induced liver cirrhosis. In this work, changes in serum amino acids and proteins in rats with thioacetamide-induced liver cirrhosis are reported, together with changes in enzyme activities in the liver and serum. Seventeen female Wistar rats were used. Eight rats were given 300 mg thioacetamide/l in drinking water for 4 months and nine rats were given water ad libitum during the same time-period. Significant increases in glycine, alanine, serine, methionine, glutamate, ornithine, phenylalanine, tyrosine, histidine and proline were observed in rats with the resulting experimental liver cirrhosis. Threonine, taurine, glutamine, lysine and citrulline tended to increase while isoleucine, leucine, aspartate, arginine and tryptophan tended to decrease. Total and nonessential amino acids increased significantly in cirrhotic animals. Total essential and aromatic amino acids tended to increase in the thioacetamide-treated group, whereas branched chain amino acids tended to decrease in the same group. Regarding serum proteins, a decrease in albumin concentration in the thioacetamide-treated animals was the only change detected. The liver enzyme activities under observation (aspartate and alanine aminotransferases, glutamate dehydrogenase and threonine deaminase) were lower in the thioacetamide group. Decreases were significant for both transaminases and threonine deaminase. Results for serum activities showed that transaminases did not change in thioacetamide-treated rats in comparison with controls. In contrast, alkaline phosphatase rose dramatically in cirrhotic rats. We conclude that the serum amino acid pattern in this chronic model of liver cirrhosis resembles in part that of the corresponding human disease.
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PMID:Serum amino acid changes in rats with thioacetamide-induced liver cirrhosis. 857 92

We have related the ratios of the protein fluorescence quenching and nucleotide absorbance time courses for the glutamate dehydrogenase catalyzed oxidative deamination of L-glutamate to identify the occurrence and sequential location of a previously demonstrated charge-transfer intermediate. Static studies showed the major portion of the fluorescence quenching signal to be due to radiationless singlet energy transfer from tryptophan to reduced coenzyme chromophores and that conformational changes contribute little to this signal. The ratio approach applied to the transient time courses shows correspondingly that, over most of the time range, the fluorescence quenching signal provides a quantitative measure of the sum of all posthydride transfer species. However, it also indicates the very early occurrence of a species of anomalous optical properties for the reaction catalyzed by the Clostridium symbiosum enzyme as well as that from bovine liver. Transient-state kinetic isotope effect time courses of both the fluorescence and the absorbance signals confirm that this species must be the prehydride charge-transfer complex in both enzyme reactions. Kinetic analysis of alpha-deuterio- and alpha-protio-L-glutamate reaction time courses proves the kinetic competence of the assignments. These results also demonstrate that the intramolecular transfer of a proton from the alpha-amino group of the substrate to an immediately adjacent aspartate carboxylate group on the enzyme is an obligatory initial event in the reactions catalyzed by both enzyme species, even though the occurrence of protein release from a critical lysine residue to the solvent occurs at different phases in those two reactions. The abnormally low intrinsic KIE required to simulate both the alpha-deuterio-L-glutamate reaction and its protio counterpart implies that the transition state of the hydride transfer step must be highly asymmetric.
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PMID:Mechanistic interpretation of tryptophan fluorescence quenching in the time courses of glutamate dehydrogenase catalyzed reactions. 898 81

Fluorescence techniques have been used to study the structural characteristics of many proteins. The halophilic enzyme NADP-glutamate dehydrogenase from Haloferax mediterranei is found to be a hexameric enzyme composed of identical subunits. Fluorescence spectra of native and denatured halophilic and bovine glutamate dehydrogenase (h-GDH and b-GDH) have been analysed. Native h-GDH presents the maximum emission at 338 nm, whereas for b-GDH the maximum appears at 332 nm. The denaturation process is accompanied by an exposure to the solvent of the tryptophan residues, as manifested by the red shift of the emission maximum in both cases. The unfolding of h-GDH is a gradual process, which is accompanied by a loss in enzyme activity. Fluorescence quenching by external quenchers, KI and acrylamide, has also been carried out. The tryptophan residues in the protein are more exposed to the solvent in h-GDH than in b-GDH. The total amount of tryptophan residues is nearly the same for both enzymes.
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PMID:Fluorescence and quenching comparative studies of halophilic and bovine glutamate dehydrogenase. 1009 14

Fluorescence techniques have been used to study the structural characteristics of many proteins. The thermophilic enzyme NAD-glutamate dehydrogenase from Thermus thermophilus HB8 is found to be a hexameric enzyme. Fluorescence spectra of native and denatured protein and effect of denaturants as urea and guanidine hydrochloride on enzyme activity of thermophilic glutamate dehydrogenase (t-GDH) have been analyzed. Native t-GDH presents the maximum emission at 338 nm. The denaturation process is accompanied by an exposure to the solvent of the tryptophan residues, as manifested by the red shift of the emission maximum. Fluorescence quenching by external quenchers, KI and acrylamide, has also been carried out.
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PMID:Denaturation studies by fluorescence and quenching of thermophilic protein NAD+-glutamate dehydrogenase from Thermus thermophilus HB8. 1296 29

The acid-induced unfolding of bovine liver glutamate dehydrogenase (GDH) was studied using various spectroscopic methods such as far- and near-UV circular dichroism (CD), intrinsic and 1-anilino naphthalene-8-sulphonate (ANS) extrinsic fluorescence spectroscopy, light scattering and fluorescence quenching in 20 mM mixed buffer at various pHs. CD spectra show that at pH 3.5, GDH retains its secondary structure substantially, whereas its tertiary structure content is reduced considerably. Intrinsic fluorescence of GDH and ANS binding suggest that, at pH 3.5, the hydrophobic surface of enzyme is more exposed in comparison to the native form. Acrylamide quenching indicates more exposure of tryptophan residues of enzyme at pH 3.5 in comparison to pH 7.5. Another partially unfolded intermediate was detected at pH 5.0, which with its ANS binding capacity lies between the pH 3.5 intermediate and the native form of the enzyme. Gel filtration results revealed that the enzyme at pH 3.5 is dissociated into trimeric species whereas it exists as hexamer at pH 7.5 and 5.0. All the data taken together suggest the existence of two partially unfolded states of GDH at moderate acidic pHs which may be considered as molten and pre-molten globule-like states.
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PMID:Partially folded conformations of bovine liver glutamate dehydrogenase induced by mild acidic conditions. 1751 89

Short-term machine perfusion after liver retrieval from non-heart-beating donors has been considered a beneficial means to reverse deleterious priming of the predamaged organ. In this study, the possible impact of different temperatures during aerobic perfusion was addressed, focusing on liver metabolic functions, structural integrity, and vascular activation. Livers retrieved 30 minutes after cardiac arrest of male Wistar rats (200-300 g) were preserved with histidine-tryptophan-ketoglutarate (HTK) solution for 18 hours by simple cold storage (CS) or subjected to short-term resuscitation (STR) with oxygenated (pO(2) > 500 mm Hg) machine perfusion with HTK at 4 degrees C, 12 degrees C, or 22 degrees C for 2 hours with subsequent CS for 16 hours at 4 degrees C. Upon reperfusion in a normothermic perfusion circuit, STR significantly improved enzyme leakage (alanine aminotransferase, glutamate dehydrogenase) and metabolic recovery (tissue levels of ATP) providing best values at 12 degrees C or 22 degrees C. Moreover, a hugely increased gene expression of the adhesion molecule ICAM-1 as well as major histocompatibility complex (MHC) class II antigen was seen after CS, but significantly alleviated by STR at 4 degrees C or 12 degrees C. However, mRNA for both surface proteins rose significantly after STR at 22 degrees C compared with CS. In conclusion, STR by oxygenated perfusion is beneficial to the predamaged graft, facilitating later transportation and supervision of the graft compared with continuous machine preservation. However, increased perfusion temperature should be recommended only up to the limit of 12 degrees C to prevent overactivation of surface antigen expression.
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PMID:Short-term resuscitation of predamaged donor livers by brief machine perfusion: the influence of temperature. 1910 Mar 81

The continuous shortage of organs necessitates the use of marginal organs from donors with various diseases, including arrhythmia-associated cardiac failure. One of the most frequently used anti-arrhythmic drugs is amiodarone (AM), which is given in particular in emergency situations. Apart from its anti-arrhythmic actions, AM provides anti-oxidative properties in cardiomyocytes. Thus, we were interested in whether AM donor pretreatment affects the organ quality and function of livers procured for preservation and transplantation. Donor rats were pretreated with AM (5 mg/kg of body weight) 10 minutes before flush-out of the liver with a cold (4 degrees C) histidine-tryptophan-ketoglutarate solution (n = 8). Livers were then stored for 24 hours at 4 degrees C before ex situ reperfusion with a 37 degrees C Krebs-Henseleit solution for 60 minutes in a nonrecirculating system. At the end of reperfusion, tissue samples were taken for histology and Western blot analysis. Animals with vehicle only (0.9% NaCl) served as ischemia/reperfusion controls (n = 8). Additionally, livers of untreated animals (n = 8) not subjected to 24 hours of cold ischemia served as sham controls. AM pretreatment effectively attenuated lipid peroxidation, stress protein expression, and apoptotic cell death. This was indicated by an AM-mediated reduction of malondialdehyde, heme oxygenase-1, and caspase-3 activation. However, AM treatment also induced mitochondrial damage and hepatocellular excretory dysfunction, as indicated by a significantly increased glutamate dehydrogenase concentration in the effluate and decreased bile production. In conclusion, AM donor pretreatment exerts anti-oxidative actions in liver preservation and reperfusion. However, these protective AM actions are counteracted by an induction of mitochondrial damage and hepatocellular dysfunction. Accordingly, AM pretreatment of donors for anti-arrhythmic therapy should be performed with caution.
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PMID:Amiodarone pretreatment of organ donors exerts anti-oxidative protection but induces excretory dysfunction in liver preservation and reperfusion. 1956 10

Fatty livers are particularly susceptible to mitochondrial alterations after cold preservation. We thus aimed to improve graft integrity by brief hypothermic oxygenation prior to warm reperfusion. Macrovesicular steatosis was induced in rat livers by fasting and subsequent feeding of a fat-free diet enriched with carbohydrates. Fatty livers were retrieved and stored ischemically at 4 degrees C for 20 hours in histidine-tryptophan-ketoglutarate solution. Hypothermic reconditioning (HR) was performed in some livers by insufflation of gaseous oxygen via the caval vein during the last 90 minutes of preservation. Viability was assessed upon isolated reperfusion. HR resulted in a significant (approximately 5-fold) reduction of parenchymal (alanine aminotransferase and lactate dehydrogenase) and mitochondrial (glutamate dehydrogenase) enzyme release. Functional recovery (bile production, oxygen consumption, and tissue levels of adenosine triphosphate) was significantly improved by HR. In untreated grafts, cellular autophagy (cleavage of LC3B and protein expression of beclin-1) was significantly impaired (<50% of baseline) after preservation/reperfusion but was restored to normal values by HR. HR also increased cleavage of caspase 9 (P < 0.5) and caspase 3 enzyme activity (by a factor of 1.5). In contrast, histological signs of tissue necrosis were abundant after reperfusion in untreated livers and largely abrogated in reconditioned livers. In conclusion, HR limits mitochondrial defects and restores basal rates of cellular autophagy. This may represent a rescue mechanism for maintaining cellular homeostasis and tissue survival.
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PMID:Impaired autophagic clearance after cold preservation of fatty livers correlates with tissue necrosis upon reperfusion and is reversed by hypothermic reconditioning. 1956 17

The guiding principle of the IAS Medal Lecture and of the research it covered was that searching mathematical analysis, depending on good measurements, must underpin sound biochemical conclusions. This was illustrated through various experiences with the amino acid dehydrogenases. Topics covered in the present article include: (i) the place of kinetic measurement in assessing the metabolic role of GDH (glutamate dehydrogenase); (ii) the discovery of complex regulatory behaviour in mammalian GDH, involving negative co-operativity in coenzyme binding; (iii) an X-ray structure solution for a bacterial GDH providing insight into catalysis; (iv) almost total positive co-operativity in glutamate binding to clostridial GDH; (v) unexpected outcomes with mutations at the catalytic aspartate site in GDH; (vi) reactive cysteine as a counting tool in the construction of hybrid oligomers to probe the basis of allosteric interaction; (vii) tryptophan-to-phenylalanine mutations in analysis of allosteric conformational change; (viii) site-directed mutagenesis to alter substrate specificity in GDH and PheDH (phenylalanine dehydrogenase); and (ix) varying strengths of binding of the 'wrong' enantiomer in engineered mutant enzymes and implications for resolution of racemates.
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PMID:Making biochemistry count: life among the amino acid dehydrogenases. 2142 13


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