A new glutamate dehydrogenase from Halobacterium halobium with different coenzyme specificity

• 1.1. Halobacterium halobium has two chromatographically distinct forms of glutamate dehydrogenase which differ in their thermolability and other properties. One glutamate dehydrogenase utilizes NAD, the other NADP as a coenzyme.
• 2.2. The NADP-specific glutamate dehydrogenase (EC 1.4.1.4) was purified 65-fold from crude extracts of H. halobium.
• 3.3. The Michaelis constants for 2-oxoglutarate (13.3 mM), ammonium (3.1 mM) and NADPH (0.077 mM) indicate that the enzyme catalyzes in vivo the formation of glutamate from ammonium and 2-oxoglutarate.
• 4.4. The amination of 2-oxoglutarate by NADP-specific glutamate dehydrogenase is optimal at the pH value of 8.0–8.5. The optimal NaCl or KCl concentration for the reaction is 1.6 M.
• 5.5. None of the several metabolites tested for a possible role in the regulation of glutamate dehydrogenase activity appeared to exert an appreciable influence on the enzyme.
• 6.6. NAD- and NADP-dependent glutamate dehydrogenases from H. halobium showed apparent molecular weights of 148,000 and 215,000 respectively.

     

Role of glutamate dehydrogenase reaction in the control of citrate pool in yeast

• 1.1. Role of NADP-glutamate dehydrogenase in the depletion of citrate was analyzed using permeabilized yeast cells.
• 2.2. Citrate was converted to 2-oxoglutarate, which was then metabolized to glutamate by NADP-glutamate dehydrogenase in the presence of ammonium ion.
• 3.3. Formation of 2-oxoglutarate plus glutamate was in good agreement with the concentration of citrate decreased. Glutamate formation can be a good indicator of the depletion of citrate, because 70% of the citrate decreased was converted to glutamate.
• 4.4. Glycolytic activity was closely correlated with the decrease in citrate under the in situ conditions.
• 5.5. NADP-glutamate dehydrogenase increased in anaerobically grown yeast cells.
• 6.6. An effective depletion of citrate by increased synthesis of NADP-glutamate dehydrogenase can explain the lowered mechanism of citrate causing glycolytic stimulation under the anaerobic growth conditions of yeast.

     

Activities of the three ammonia-forming enzymes in the tissues of the brackish-water bivalve Corbicula japonica

• 1.1. Activities of the three ammonia-forming enzymes, glutamate dehydrogenase, AMP deaminase and serine dehydrase (SerDH), were measured in tissues of gill, digestive diverticula, mantle and foot muscle of the brackish-water bivalve Corbicula japonica.
• 2.2. High levels of SerDH activity were detected in gill and digestive diverticula, while the activity levels of the other two enzymes were low.
• 3.3. The result suggests the significance of SerDH in amino acid degradation of this species.

     

Superoxide dismutase,reduced glutathione and TBA-reactive products in erythrocytes of patients with multiple sclerosis

• 1.1. Superoxide dismutase, reduced glutathione and lipid peroxides levels were determined in the erythrocytes of multiple sclerosis patients.
• 2.2. Superoxide dismutase activity and the malonyldialdehyde production rate were found to be significantly enhanced.
• 3.3. The isoelectric focusing pattern of Superoxide dismutase from multiple sclerosis and normal subjects erythrocytes was substantially overlapping.
• 4.4. Our results indicate the occurrence of a higher susceptibility of multiple sclerosis erythrocytes to lipid peroxidation.

     

Beef liver glutamate dehydrogenase : Effects of partial proteolysis with chymotrypsin

• 1.1. After chymotryptic digestion of bovine glutamate dehydrogenase, the assay conditions determine whether activation or inhibition is observed.
• 2.2. The major fragments appear to remain physically associated.
• 3.3. Responses to both GTP and ADP are altered. Inhibition by GTP at pH 7 and 8 is almost abolished.
• 4.4. Out of various ligand combinations tested, GTP and NADH together provide the best protection against all the proteolytic effects.

     

Beef liver glutamate dehydrogenase: A study of the oxidation of various alternative amino acid substrates retaining the correct spacing of the two carboxylate groups

• 1.1. Several glutamate analogues substituted at the β- or γ-carbon atoms have been tested as substrates for glutamate dehydrogenase.
• 2.2. The two γ-methyl derivatives and DL-β-methylglutamate give the same pH optimum (8.7) as l-glutamate, but show inhibition by ADP and activation by GTP at pH 8, unlike glutamate and like the monocarboxylic substrate l-norvaline, which gives a pH optimum of 10.
• 3.3. l-γ-methyleneglutamate, the poorest substrate tested (0.28% of rate with glutamate) gives a high pH optimum (10), like norvaline, but shows marked activation by both ADP (13-fold) and GTP (27-fold).
• 4.4. Despite the correct dicarboxylate spacing, all the analogues were much poorer substrates than l-norvaline.

     

Responses of mixed-function oxygenase and antioxidase enzyme system of Mytilus sp. to organic pollution

• 1.1. Mixed-function oxidase (MFO) system components (cytochrome P-450, “418-peak”, cytochrome b₅ and NADPH-cytochrome c (P-450) reductase) and inducible antioxidant enzymes (catalase, Superoxide dismutase (SOD), glutathione peroxidase (GPX) and DT-diaphorase) has been determined in digestive glands of mussels (Mylilus galloprovincialis) collected from three Mediterranean coastal locations, exhibiting an organic pollution gradient.
• 2.2. Cytochrome P-450, the “418-peak”, catalase and SOD showed a good correlation with whole body tissue PAHs and, to a lower extent, with PCBs.
• 3.3. Microsomal NADPH-dependent DT-diaphorase, but not the NADH-dependent microsomal enzyme or the cytosolic DT-diaphorases, was indicated to increase with pollution exposure.
• 4.4. The application of such measurements to environmental monitoring is discussed. Given the magnitude of differences observed, and the state of knowledge on enzyme function and mechanisms of toxicity, a multiparameter approach is considered to offer current and future potential for detecting the impact of organic pollution on bivalve molluscs.

     

Glycolytic enzymes of fowl and turkey spermatozoa

• 1.1. It was confirmed that, under anaerobic conditions, fowl spermatozoa formed lactate from glucose thirteen times faster than turkey spermatozoa.
• 2.2. The profiles of glycolytic enzyme activities were similar for spermatozoa from both species; however fowl spermatozoal activities were generally 2- to 4-fold higher.
• 3.3. Exceptions were glycerophosphate mutase and lactate dehydrogenase activities which were respectively 9.5 and 41 times greater in fowl spermatozoa.
• 4.4. In both species, spermatozoal glyceraldehyde-3-phosphate dehydrogenase had the lowest activity of the glycolytic enzymes.

     

One and two dimensional isoelectric focusing of lactate dehydrogenase from the tissues of Ovis aries

• 1.1. Lactate dehydrogenase in ovine tissues was separated by electrophoresis, one dimensional isoelectric focusing (IEF) and a two dimensional technique.
• 2.2. Tissues showed five zones of enzyme activity consisting of multiple bands after IEF.
• 3.3. The IEF zymograms were unique for each tissue and differed from those of other species.
• 4.4. Two dimensional separation revealed that the five zones of activity observed on IEF corresponded to the five isoenzymes separable by conventional electrophoresis.

     

Influence of handling and/or anaesthesia on stress response in rainbow trout. Effects on liver primary metabolism

• 1.1. The overall effect of handling, anaesthesia and sham injection on some blood metabolites, liver glycogen and several key enzymes involved in liver carbohydrates and nitrogen metabolism was studied in rainbow trout. In addition, the possible role of anaesthesia (MS222) itself as a stress-inductor or suppressor was also studied.
• 2.2. Stress resulted in hyperglycaemia and initially in liver glycogen depletion, as well as increasing plasma amino acid levels.
• 3.3. Glycogen stores subsequently recovered while amino acid concentration fell.
• 4.4. These changes seemed to correlate with the increased activity of liver fructose 1,6-bisphosphatase, glucose 6-phosphate dehydrogenase, alanine aminotransferase and glutamate dehydrogenase, thus supporting the hypothesis that gluconeogenic flux from amino acids increases in stressed trouts.
• 5.5. Anaesthesia, under the same experimental conditions, did not seem to mediate in stress production, but rather resulted in stress suppression.

     

Distribution of opine dehydrogenases and lactate dehydrogenase activities in marine animals

• 1.1. Opine dehydrogenases (OpDHs) and lactate dehydrogenase (LDH) activities were determined in various marine animals. OpDHs were detected in six marine invertebrate phyla; Porifera, Coelenterata, Annelida, Mollusca, Arthropoda and Echinodermata in phylogenic sequence.
• 2.2. Among several OpDHs, tauropine dehydrogenase (TaDH) occurred widely in marine invertebrates, from Porifera to Echinodermata.
• 3.3. With a few exceptions, total OpDHs activities exceeded that of LDH activity in the marine invertebrates investigated.
• 4.4. With respect to anaerobic glycolysis, OpDHs are indicated to play an important role in phylogenically lower invertebrates, whereas LDH is more important in higher animals.

     

The effect of initiated involution on enzyme activity and substrate uptake by the mammary gland of the lactating rabbit

• 1.1. Arteriovenous difference studies across the lactating rabbit mammary gland for glucose, acetate, triacylglycerol and non-esterified fatty acids during initiated involution are reported.
• 2.2. A significant reduction in substrate utilisation is paralleled by a decrease in the activities of fatty acid synthetase, acetyl CoA synthetase, citrate synthase and glutamate dehydrogenase in biopsy samples taken from the gland.
• 3.3. Results from the analysis of lipid fractions within the gland during this period are discussed in relation to lipid resorption.

     

The erythrocytes of the metallic skink Niveoscineus metallicus

• 1.1. We studied the haemoglobin content, erythrocyte indices, erythrocyte enzymes and haemoglobin electrophoresis patterns of the metallic skink Niveoscineus metallicus and compared them to the small amount of published data on other small lizards.
• 2.2. Haemoglobin was much lower than that recorded for the salamander.
• 3.3. Erythrocyte enzymes (glucose phosphate isomerase and glucose 6 phosphate dehydrogenase) were lower in the skink than in the salamander. Glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase and pyruvate kinase were much higher in the skink than in the salamander.
• 4.4. A single, slow, haemoglobin component was identified by electrophoresis.

     

The myelo-erythroid nature of the chloragogenous-like tissues of the annelids

• 1.1. Chloragogenous, extravasal, intravasal and botryoidal tissues occur alternatively in various types of annelids. These tissues are sources of extracellular respiratory pigments. Considering their peritoneal origin, their structural and functional similarities we propose the term “chloragogenous-like tissues” for their common designation.
• 2.2. The synthesis of haem-compounds plays a significant role in the development of the structural and functional characteristics of the chloragogenous tissues. Haemoglobin is released into the blood plasma but the haem-enzymes catalase and peroxidase accumulate into the chloragocytes, moreover haem by products and damaged haem-compounds may be involved in the formation of chloragosomes.
• 3.3. Chloragocytes are in some way involved in the immune defence reactions.
• 4.4. We conclude that the chloragogenous-like cells are specific myelo-erythroid cells of the annelids.

     

Some properties of the nadp+dependent isocitrate dehydrogenase of rat and pig ovary

• 1.1. Cytosolic isocitrate dehydrogenase from rat and pig ovaries differs from that described in other tissues. It is more labile, has higher K_m-values for substrates, higher optimal pH, and its activity is modulated by varying ratios of Ca²⁺: Mg²⁺. The ovarian enzyme exhibits acute and long term responses to in vivo administration of gonadotropins.
• 2.2. A partial purification yielding a 70-fold increase in specific activity of this NADP⁺ dependent enzyme is described. The enzyme mol wt = 58,000 ± 3000 daltons and pI = 4.9.
• 3.3. The unique properties of the enzyme are discussed in relation to its probable metabolic role in ovary.

     

Enzyme activities in human breast tumours.

The activities of six enzymes associated with carbohydrate metabolism were measured both in carcinomas and in normal breast tissues. The following differences were observed. 1. The carcinoma showed higher enzyme activities than the normal mammary tissue. 2. The ratios of glutamate dehydrogenase, hydroxybutyrate dehydrogenase, glutathione reductase and catalase to lactate dehydrogenase were lower in carcinomas than in normal tissues. Similarly, the ratios of glutamate dehydrogenase, hydroxybutyrate dehydrogenase, glutathione reductase and catalase to glucose-6-phosphate dehydrogenase were also significantly lower in carcinomas. 3. There were no significant differences in enzyme activities between I and II stage of the disease and the metastatic tissues, however, there were significant differences between I and III stage. The significance of these findings is discussed in terms of the alterations in the balance between the metabolic pathways.     

Cellular and intracellular localization of catalase and acid phosphatase in the midgut of Lumbricus terrestris L.: A cell fractionation study

• 1.1. Cellular and intracellular localization of catalase and acid phosphomonoesterase in the midgut of Lumbricus terrestris was studied by use of tissue fractionation.
• 2.2. At least 60–70% of the catalase resides in the chloragocyte cytosol and the remaining 30–40% resides in gut epithelium peroxisomes.
• 3.3. One of the main functions of the chloragocyte catalase is probably scavenging for H₂O₂ arising from the interaction between blood heme-protein and oxygen.
• 4.4. A simple method for the histochemical detection of cytosol catalase is proposed.
• 5.5. About 10% of the gut acid phosphatase resides in chloragocyte lysosomes. The chloragosomes contain no acid phosphatase.

     

A one-step pmr determination of hydrogen transfer stereospecificity of NADP+-linked oxidoreductases

• 1.1. A simple, facile one-step method has been devised to measure the stereospecificity of NADP⁺-linked oxidoreductases. The procedure involves coupling the test enzymes to enzymes of known stereospecificity in the presence of deuterated substrates. The regenerated NADP⁺ in the coupled reactions is analyzed by PMR for its deuterium content at the carbon-4 position of the nicotinamide ring.
• 2.2. It is found that malate dehydrogenase (EC 1.1.1.37). lactate dehydrogenase (EC 1.1.1.27) and glycerate dehydrogenase (EC 1.1.1.29) are A-side stereospecific whereas glutamate dehydrogenase (EC 1.4.1.3) and glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) are B-side stereospecific.
• 3.3. Enzymes which can utilize both NAD⁺ and NADP⁺ have the same stereospecificity with respect to the coenzyme.

     

Influence of repeated hyperthermia on the early development of carcinogen-induced rat mammary cancers; Refinement of a technique for hyperthermia research

• 1.1.|Hyperthermia (c. 41°C) occurs in mammals (e.g. humans) during normal life-history events such as fever and vigorous exercise. The effects of such episodic hyperthermia on early developmental stages of cancer are of potential importance, yet have been investigated hardly at all.
• 2.2.|We injected female Sprague-Dawley rats with the mammary-gland carcinogen 7,12-dimethylbenzathracene and, over a 4-week period before cancer onset, subjected them to 20 1-h episodes of whole-body hyperthermia (41.2°C colonic) to determine effects on subsequent appearance of carcinomas.
• 3.3.|Hyperthermia did not have significant effects on the development of clinical disease in this system, indicating that precancerous or incipient cancerous cells are not susceptible to damage by the levels of hyperthermia associated with normal life-history events.
• 4.4.|For repeated induction of hyperthermia with minimal confounding effects of stress, we refined a technique in which hyperthermia-treated animals, as well as controls, were anesthetized with sodium pentabarbital during thermal treatments, thus suppressing thermoregulation and higher brain functions.