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:1.1.1.27 (lactate dehydrogenase)
29,211 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane fractions with L-lactate dehydrogenase, sn-glycerol-3-phosphate (G3P) dehydrogenase, and nitrate reductase activities were prepared from Staphylococcus aureus wild-type and hem mutant strains. These preparations reduced ferric to ferrous iron with L-lactate or G3P as the source of reductant, using ferrozine to trap the ferrous iron. Reduction of ferric iron was insensitive to 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO) with either L-lactate or G3P as reductant, but oxalate and dicumarol inhibited reduction with L-lactate as substrate. The membranes had L-lactate- and G3P-nitrate reductase activities, which were inhibited by azide and by HQNO. Reduction of ferric iron under anaerobic conditions was inhibited by nitrate with preparations from the wild-type strain. This effect of nitrate was abolished by blocking electron transport to the nitrate reductase system with azide or HQNO. Nitrate did not inhibit reduction of ferric iron in heme-depleted membranes from the hem mutant unless hemin was added to restore L-lactate- and G3P-nitrate reductase activity. We conclude that reduced components of the electron transport chain that precede cytochrome b serve as the source of reductant for ferric iron and that these components are oxidized preferentially by a functional nitrate reductase system.
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PMID:Reduction of ferric iron by L-lactate and DL-glycerol-3-phosphate in membrane preparations from Staphylococcus aureus and interactions with the nitrate reductase system. 20 71

The activities of twelve enzymes were measured in crude extracts from cells of Escherichia coli K-10 grown aerobically or anaerobically in a defined medium in the presence or absence of nitrate. The activities of isocitrate dehydrogenase, aconitate hydratase, 2-oxoglutarate dehydrogenase, malate dehydrogenase, malic enzyme, and D-lactate dehydrogenase (NAD+-independent) were found to be higher in cells grown in nitrate respiration than in those in fermentation, but lower than in those in respiration. This finding may explain the incomplete oxidation in nitrate respiration and, on the other hand, suggests the operation of the tricarboxylic acid even under these conditions. The activities of succinate dehydrogenase and alcohol dehydrogenase in relation to the formation of fermentation product were as high in cells grown in fermentation as in those in respiration and were low in those in nitrate respiration. However, that ratio of the activities in the latter case to the activities in respiration was the same as the ratio for most enzymes in the tricarboxylic acid cycle. The level of lactate dehydrogenase (NAD+-dependent) was not affected by nitrate respiration but its activity in the extract was inhibited by nitrate and nitrite. The absence of lactate in the anaerobic culture with nitrate may be due to this inhibition as well as NADH oxidation by nitrate. Levels of glucose-6-phosphate dehydrogenase and glutamate dehydrogenase were not altered by the growth conditions and that of pyruvate dehydrogenase was low only in cells grown in fermentation.
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PMID:Effect of nitrate reduction on the enzyme levels in carbon metabolism in Escherichia coli. 77 52

1. In an attempt to determine the mechanism whereby enzymes are removed from the circulating plasma, purified rabbit-muscle lactate dehydrogenase-5 was labelled with 125I and injected intravenously into rabbits. During the first hour after injection enzyme activity and radioactivity disappeared from the plasma at comparable fast rates, which are attributed mainly to distribution of the enzyme throughout the extracellular fluid. This was followed by a phase lasting about 7 h during which enzyme activity disappeared at a faster rate than the radioactivity, an observation indicating either intravascular breakdown of the enzyme protein or its degradation in the tissues, followed by release of labelled fragments into the circulation. Enzyme activity then reached a constant value and the plasma radioactivity continued to decrease at a slower exponential rate; it is suggested that this is due to removal of breakdown products. 2. The radioactivity of the tissues was measured at various time-intervals after injection. After 2 h and 8 h highest concentrations were found in the spleen, liver, jejunum and duodenum. Relatively high concentrations were also found in the intestinal juices throughout the period of study, an observation which suggests that discharge via the small intestine is a major route whereby inactivated enzyme fragments are removed from the circulation. 3. About 5% of the injected radioactivity was recovered in the faeces during the first 3 days, and the urine accounted for 73% during the same period. About 35% of the urinary radioactivity was shown by silver nitrate precipitation and by chromatography to consist of free iodide and the remainder appeared to consist of radio-iodinated amino acids or peptides. Free mono- and di-iodotyrosine were identified among the products. These results suggest that further breakdown in the intestine is followed by absorption of the products, which are excreted in the urine.
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PMID:The fate of circulating lactate dehydrogenase-5 in the rabbit. 124 99

An original experimental model has been presented for studying of cytoprotection of non-stimulated leukocytes. The model consists in determining of a degree of inhibition of the release of lactic acid dehydrogenase (LDH) by isolated human neutrophils (PMNs) in the course of their "ageing" at the room temperature (22 degrees C). Using this model for the first time, cytoprotective action was pointed-out of following compounds: NO (EDRF) in aqueous solution; natrium nitroprusside; active metabolite of molsidomine--SIN-1; N-acetyl-S-nitroso-penicillamine (SNAP) which are believed to owe their anti-platelet and vasodilatory activity to stimulation of cyclic-GMP--and iloprost (a stable prostacyclin analogue) and prostaglandin E2 (PGE2) which activate cyclic AMP. Effectiveness of cytoprotective action of these compounds increased as follows: NO (IC50 = 58.4) less than PGE2 (IC50 = 38) less than SIN-1 (IC50 = 9.2) less than SNAP (IC50 = 3.2) less than natrium nitroprusside (IC50 = 1.2) less than iloprost (IC50 = 0.2)(nmoles/5 x 10(6) PMNs; moreover, iloprost and SIN-1 showed a synergic action. Among ++nitroso-vasodilators, nitroglycerin had no cytoprotective action; it may indicate that to achieve cytoprotection in leukocytes a nitro- vasodilator should contain in its chemical structure -NO group and not -NO3 group, as it is in nitroglycerin. In neutrophils stimulated with calcium ionophore, arachidonic acid or FMLP, nitro-vasodilators are of no influence on production of superoxide anions O2-, hydroxyeicosatetraenoic acids (5-HETE and 12-HETE) and leukotriene B4. A hypothesis has been put forward on the relationship of function of c-GMP and c-AMP in the mechanism of cytoprotection of human leukocytes.
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PMID:[Cytoprotective action of guanylate cyclase stimulators on human leukocytes]. 169 93

We investigated the effect of lead nitrate (0.1, 1.0, 10 or 20 microM) on the metabolism of glycosaminoglycans (GAG) in confluent cultures of bovine aortic endothelial cells. It was found that lead at 10 and 20 microM significantly decreased the accumulation of [35S]sulfate-labeled GAG ([35S]GAG) both in the cell layer and the medium after a 24-h culture. A time course study showed that 10 microM lead decreased the accumulation of [3H]glucosamine-labeled GAG both in the cell layer and the medium after 24 h and longer. The release of [35S]GAG from the cell layer during the last 3 h of a 24 h culture was not changed by lead. The detachment of [3H]thymidine-labeled cells from the monolayer was unaffected by lead. It was shown that lead at 10 microM decreased both heparan sulfate and the other GAG in the cell layer; the former was more sensitive to lead treatment. Lead at 20 microM and below failed to increase the release of lactate dehydrogenase, suggesting that non-specific cell damage was not caused by lead. From these results, it was suggested that lead decreases endothelial cell heparan sulfate content through a decrease in the GAG production without a non-specific cell damage. Lead may be a risk factor of vascular disorders.
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PMID:Effect of lead on the glycosaminoglycans metabolism of bovine aortic endothelial cells in culture. 189 98

In order to study the difference of uptake and distribution between hexavalent (Cr6+) and trivalent (Cr3+) chromium in isolated rat hepatocytes, the cells were incubated with Cr6+ or Cr3+ (1 mM Cr) at 37 degrees C for up to 60 min. Leakage of lactate dehydrogenase from the hepatocytes into the suspension medium as an indicator of cellular injury was facilitated by Cr6+ (K2Cr2O7) at 60 min of incubation, whereas Cr3+ [Cr(NO3)3] had no effect. After 60 min of incubation with Cr6+, about 33% of the added Cr was found in the hepatocytes, whereas incubation with Cr3+ resulted in transfer of about 66% of the added Cr to the cells. After 20 and 40 min of incubation with Cr6+, about 39% of cellular Cr was found in the cytosolic fraction of hepatocytes, followed by a reduction to about 35% after 60 min of incubation. However, Cr detected in the cytosolic fraction of hepatocytes incubated with Cr3+ was about 1% of cellular Cr. Cr-binding substances in the cytosolic fraction of hepatocytes incubated with Cr6+ were eluted with two Cr peaks by Sephadex G-200 chromatography. These Cr-binding substances in the low-molecular-weight fractions were separable into at least two substances by thin-layer chromatography. These results suggest that Cr6+ readily passes through the cell membrane and combines with substances already present in the cytosolic fraction of hepatocytes, unlike metallothionein induced by cadmium, followed by detoxification. Consequently, cellular injury might be induced by Cr6+ which could not combine with LMCr in the cytosolic space of the hepatocytes.
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PMID:Uptake and distribution of chromium in isolated rat hepatocytes and its relation to cellular injury. 227 59

Buffered solutions (pH 5-pH 8) of glyceryl trinitrate (GTN), sodium nitroprusside (NaNP), S-nitroso-N-acetylpenicillamine (SNAP), molsidomine and its active metabolite (SIN-1) at concentrations of 30 microM were each tested at 37 degrees C for the release of nitric oxide (NO) by its co-oxidation to NO3 along with oxidation of oxyhaemoglobin to methaemoglobin. Apart from GTN and molsidomine, three other stimulators of guanylate cyclase released NO in a pH-dependent manner. Optimum for the release of NO by SIN-1 was at pH 7.4 and therefore this guanylate cyclase stimulator was chosen for studies on interaction with the adenylate cyclase stimulator iloprost, a stable prostacyclin analogue. Human platelets, neutrophils and strips of coronary arteries were used as targets to study this interaction. SIN-1 and iloprost synergized in the inhibition of collagen-induced platelet aggregation and protection of neutrophils against the release of lactate dehydrogenase, whereas no synergism between these drugs was observed in their vasorelaxant action. It is concluded that pharmacological synergism between adenylate and guanylate cyclase stimulators is not a general rule, but occurs only in certain types of cells.
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PMID:Interaction between stimulators of adenylate and guanylate cyclases in human leukocytes, platelets and arteries. 248 90

Aluminium (Al) chloride (10-200 microM) increased the Al content in hepatocytes isolated from fed male rats in a time- and concentration-dependent manner. After 60 min of incubation with 100 microM Al about 45% of cellular Al was found each in the mitochondrial and the postmitochondrial fraction of hepatocytes, whereas about 5% of Al sedimented with nuclei and cell debris. Concomitantly, the leakage of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) increased in the presence of Al time- and concentration-dependently, but only to a moderate extent. Aluminium (10-200 microM) also accelerated the formation of lactate by hepatocytes. No significant differences were found in Al uptake and distribution and its effect on LDH leakage and lactate formation when the metal ion was given as AlCl3, Al(NO3)3 or Al(lactate)3. Al concentrations (AlCl3) exceeding 250 microM severely disturbed the determination of LDH, AST and lactate in a cell free system. The data suggest only a moderate toxicity of Al compounds to isolated hepatocytes, when given in amounts approximating (patho)physiological conditions.
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PMID:Uptake and distribution of aluminium in rat hepatocytes and its effect on enzyme leakage and lactate formation. 356 54

Primary cultures of rat vascular endothelial and smooth muscle cells were developed as models to study xenobiotic-induced cytotoxicity. Endothelial and smooth muscle cells were isolated by enzymatic digestion and mechanical dissociation of rat thoracic aortae. Optimal cell growth and minimal fibroblast contamination in cultures of both cell types were obtained in Medium 199 supplemented with 10% fetal bovine serum. Cultured cells were characterized by distinctive morphologic features and growth patterns. Intercellular endothelial cell junctions were selectively stained with silver nitrate. Endothelial cells also exhibited a nonthrombogenic surface, as reflected by platelet-binding studies. Confluent cultures of smooth muscle cells, but not endothelial cells, contracted in response to norepinephrine (10 microM). Cultures of both cell types were exposed to acrolein (2, 5 or 50 ppm), an environmental pollutant, for 4 and 24 h. Morphologic damage, lactate dehydrogenase release, and cellular thiol content were used as indices of cytotoxicity. Acrolein-induced enzyme leakage and morphologic alterations were dose- and time-dependent and more pronounced in cultures of smooth muscle cells than in endothelial cells. The total thiol content of endothelial cells exposed to acrolein (50 ppm) for 24 h was not significantly different from that of respective controls. In contrast, the content of treated smooth muscle cells was higher than that of controls. These observations show that primary cultures of vascular cells provide a useful model to evaluate xenobiotic-induced cytotoxicity. The information obtained using a cell culture system may be complemented by the use of other in vivo and in vitro models to determine the mechanisms by which xenobiotics cause vascular cell injury.
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PMID:Primary cultures of rat aortic endothelial and smooth muscle cells: I. An in vitro model to study xenobiotic-induced vascular cytotoxicity. 357 Nov

The use of bacterial membrane vesicles as an experimental system for the study of active transport has been discussed. Vesicles are prepared from osmotically sensitized bacteria, and consist of osmotically intact, membranebound sacs without internal structure. They retain litle or no cytoplasm. Under appropriate conditions, these vesicles catalyze the transport of a variety of solutes at rates which are comparable, in many cases, to those of intact cells. Two general types of transport systems have been elucidated in the vesicle system: (i) group translocation systems which catalyze vectorial covalent reactions; and (ii) respirationlinked transport systems that catalyze the active transport of a whole range of metabolites against an electrochemical or osmotic gradient. In E. coli membrane vesicles, the respiration-linked transport systems are coupled primarily to the oxidation of (D)-lactate to pyruvate, catalyzed by a flavin-linked, membrane-bound (D)-lactate dehydrogenase which has been purified to homogeneity. Electrons derived from (D)-lactate or certain artificial electron donors are transferred to oxygen by means of a membrane-bound respiratory chain, and respiration is coupled to active transport within a segment of the respiratory chain between the primary dehydrogenase and cytochrome. b(l). The great majority of the individual membrane vesicles in the population catalyze active transport, and the generation or hydtolysis of ATP is not involved. Under anaerobic conditions, fumarate or nitrate can be utilized in place of oxygen as terminal electron acceptors. With the exception that (D)-lactate is not always the most effective electron donor for active transport, vesicles prepared from a number of other organisms catalyze transport in a similar manner. Fluorescent dansylgalactosides are useful molecular probes of active transport in the vesicle system. These compounds are competitive inhibitors of beta-galactoside transport, but are not transported themselves. Fluorescence studies indicate that the lac carrier protein constitutes approximately 3 to 6 percent of the total membrane protein, and that it is not accessible to the external medium unless the membrane is "energized." Thus, energy is coupled to one of the initial steps in the transport process. Studies with a photoaffinity-labeled galactoside provide independent support for this conclusion. When membrane vesicles prepared from a (D)-lactate dehydrogenase mutant of E. coli are treated with (D)-lactate dehydrogenase, the enzyme binds to the vesicles and they regain the capacity to catalyze (D)-lactate oxidation and (D)-lactate-dependent active transport. The maximal specific transport activity obtained in the reconstituted system is similar in magnitude to that of wildtype vesicles. Titration studies with dansylgalactoside demonstrate that there is at least a seven- to eightfold excess of lac carrier protein relative to (D)-lactate dehydrogenase. Evidence is presented indicating that the enzyme is bound to the inner surface of native membrane vesicles and to the outer surface of reconstituted vesicles, and that the flavin coenzyme moiety is critically involved in binding. Possible mechanisms of respirationlinked active transport are discussed.
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PMID:Transport studies in bacterial membrane vesicles. 462 43


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