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:1.1.1.37 (malate dehydrogenase)
4,591 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in the metabolism of Crithidia fasciculata ATCC 11745 when grown in the presence of ethidium bromide were studied. Ethidium bromide-grown cells had decreased respiratory activity as measured by oxygen consumption. More than 50% of the organisms cultivated in a defined medium containing 1.0 mg/liter of ethidium bromide became dyskinetoplastic and had decreased activities of particulate succinate and NADH-linked dehydrogenases as well as of soluble isocitrate dehydrogenase. These cells also had increased activities of particulate alpha-glycerophosphate dehydrogenase, soluble alpha-glycerophosphate dehydrogenase, malic enzyme, hexokinase, and malate dehydrogenase. Ethidium bromide-grown cells had a lower level of ATP and contained less DNA than cells grown in its absence.
...
PMID:Effect of ethidium bromide on the oxidative metabolism and enzyme profiles of Crithidia fasciculata. 86 23

In the presented study the influence of freezing and freeze-drying on enzyme activity is described. Attention is paid to 16 enzymes which can be used for quantitative enzyme histochemical techniques. With the exception of succinate dehydrogenase only, no significant inactivation during freezing and freeze-drying procedures could be demonstrated with lactate dehydrogenase, malate dehydrogenase (NAD+), malate dehydrogenase (decarboxylating) (NADP+), isocitrate dehydrogenase (NADP+), glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, NADH-oxydoreductase, mitochondrial glycerol-3-phosphate dehydrogenase, cytochrome c oxidase, phosphoglucomutase, glucosephosphate isomerase, glucose-6-phosphatase, acid phosphatase, beta-glucuronidase and non specific aryl esterase. Therefore, the results supply a sound foundation for those quantitative enzyme histochemical techniques in which tissue specimens are frozen or frozen-dried before enzyme estimations are performed.
...
PMID:The influence of freezing and freeze-drying of tissue specimens on enzyme activity. 87 Apr 61

A technique for studying the catalytic activity of enzymes spread as a film at an air-water interface, by exchanging the subphase under the film to remove unspread enzyme molecules, was developed, and its effectiveness was studied using surface-spread mitochondrial malate dehydrogenase. Mitochondrial malate dehydrogenase formed stable films which gave reproducible pi-A curves. The enzyme activity was measured by the oxidation rate of reduced nicotinamide adenine dinucleotide (NADH) in the presence of the substrate oxalacetic acid. Oxalacetic acid and NADH were injected into the subphase. The catalytic activity of the enzyme was dependent on the surface pressure of the film. The maximum catalytic activity was observed at a surface pressure of 4.4 dynes/cm. The activity was higher at intermediate surface pressures than at very low or very high surface pressures. A high bulk catalytic activity was observed in the unstable region, i.e., at a high degree of compression, of the film. The catalytic activity of the surface-spread enzyme was only a fraction of an equivalent amount of enzyme in solution.
...
PMID:Enzymatic activity of pig heart mitochondrial malate dehydrogenase monomolecular films by surface exchange technique. 87 77

Cell-free extracts of Methanobacterium thermoautotrophicum were found to contain high activities of the following oxidoreductases (at 60 degrees C): pyruvate dehydrogenase (coenzyme A acetylating), 275 nmol/min per mg of protein; alpha-ketoglutarate dehydrogenase (coenzyme A acylating), 100 nmol/min per mg; fumarate reductase, 360 nmol/min per mg; malate dehydrogenase, 240 nmol/min per mg; and glyceraldehyde-3-phosphate dehydrogenase, 100 nmol/min per mg. The kinetic properties (apparent V(max) and K(M) values), pH optimum, temperature dependence of the rate, and specificity for electron acceptors/donors of the different oxidoreductases were examined. Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase were shown to be two separate enzymes specific for factor 420 rather than for nicotinamide adenine dinucleotide (NAD), NADP, or ferredoxin as the electron acceptor. Both activities catalyzed the reduction of methyl viologen with the respective alpha-ketoacid and a coenzyme A-dependent exchange between the carboxyl group of the alpha-ketoacid and CO(2). The data indicate that the two enzymes are similar to pyruvate synthase and alpha-ketoglutarate synthase, respectively. Fumarate reductase was found in the soluble cell fraction. This enzyme activity coupled with reduced benzyl viologen as the electron donor, but reduced factor 420, NADH, or NADPH was not effective. The cells did not contain menaquinone, thus excluding this compound as the physiological electron donor for fumarate reduction. NAD was the preferred coenzyme for malate dehydrogenase, whereas NADP was preferred for glyceraldehyde-3-phosphate dehydrogenase. The organism also possessed a factor 420-dependent hydrogenase and a factor 420-linked NADP reductase. The involvement of the described oxidoreductases in cell carbon synthesis is discussed.
...
PMID:Oxidoreductases involved in cell carbon synthesis of Methanobacterium thermoautotrophicum. 91 79

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

Temperature studies have indicated that from 0 to 37 degrees, the time-dependent inactivation of mitochondrial malate dehydrogenase from porcine heart by pyridoxal 5-phosphate (pyridoxal-5-P) is biphasic. The initial phase of the inactivation is reversible but can be made irreversible by reduction with sodium borohydride. The reduced pryidoxal-5-P-enzyme adduct exhibits a new absorbance maximum at 325 nm and a fluorescence emission at 392 nm when excited at 325. The irreversible second phase of the inactivation is accompanied by the appearance of a new 325-nm absorbance maximum, in the absence of reduction, and a fluorescence emission centered about 390 to 400 nm when excited at 325. The evidence presented suggests the formation of a Schiff base between pyridoxal-5-P and a nucleophilic residue, most likely lysine, of malate dehydrogenase during the first phase of inactivation. An X-azolidine-like structure, a further derivative of the Schiff base, possessing spectral properties consistent with the reported data, may be formed during the second phase; this presumably involves a second nucleophilic residue of the enzyme, implicating the action of pyridoxal-5-P as a bifunctional reagent in this instance. The presence of the coenzyme, NADH, protects the enzyme from inactivation, suggesting that pyridoxal-5-P interacts at or near the malate dehydrogenase active center. Simultaneous binding studies using pyridoxal-5-P with known malate dehydrogenase competitive inhibitors AMP, ADP, and nicotinamide indicate that the pyridoxal-5-P modification occurs in the general area of the ADP portion of the coenzyme binging site. Furthermore, the presence of nicotinamide enhances pyridoxal-5-P binding to and inactivation of malate dehydrogenase.
...
PMID:Biphasic inactivation of procine heart mitochondrial malate dehydrogenase by pyridoxal 5'-phosphate. 111 83

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

The inactivation of cytoplasmic malate dehydrogenase (L-malate: NAD+ oxidoreductase, EC 1.1.1.37) from porcine heart and the specific modification of arginyl residues have been found to occur when the enzyme is inhibited with the reagent butanedione in sodium borate buffer. The inactivation of the enzyme was found to follow pseudo-first order kinetics. This loss of enzymatic activity was concomitant with the modification of 4 arginyl residues per molecule of enzyme. All 4 residues could be made inaccessible to modification when a malate dehydrogenase-NADH-hydroxymalonate ternary complex was formed. Only 2 of the residues were protected by NADH alone and appear to be essential. Studies of the butanedione inactivation in sodium phosphate buffer and of reactivation of enzymatic activity, upon the removal of excess butanedione and borate, support the role of borate ion stabilization in the inactivation mechanism previously reported by Riordan (Riordan, J.F. (1970) Fed. Proc. 29, Abstr. 462; Riordan, J.F. (1973) Biochemistry 12, 3915-3923). Protection from inactivation was also provided by the competitive inhibitor AMP, while nicotinamide exhibited no effect. Such results suggest that the AMP moiety of the NADH molecule is of major importance in the ability of NADH to protect the enzyme. When fluorescence titrations were used to monitor the ability of cytoplasmic malate dehydrogenase to form a binary complex with NADH and to form a ternary complex with NADH and hydroxymalonate, only the formation of ternary complex seemed to be effected by arginine modification.
...
PMID:Identification of essential arginyl residues in cytoplasmic malate dehydrogenase with butanedione. 115 61

Palmitylcarnitine oxidation by isolated liver mitochondria has been used to investigate the interaction of fatty acid oxidation with malate, glutamate, succinate, and the malate-aspartate shuttle. Mitochondria preincubated with fluorocitrate were added to a medium containing 2mM ATP and ATPase. This system, characterized by a high energy change, allowed titration of respiration to any desired rate between States 4 and 3 (Chance, B., and Williams, G. R. (1956) Adv. Enzymol. Relat. Areas Mol. Biol. 17, 65-134). When respiration (reference, with palmitylcarnitine and malate as substrates) was set at 75% of State 3, the oxidation of palmitylcarnitine was limited by acetoacetate formation. The addition of malate or glutamate approximately doubled the rate of beta oxidation. Malate circumvented this limitation by citrate formation, but the effect of glutamate apparently was due to enhancement of the capacity for ketogenesis. The rate of beta oxidation was curtailed when malate and glutamate were both present. This curtailment was more pronounced when the malate-aspartate shuttle was fully reconstituted. Among the oxidizable substrates examined, succinate was most effective in inhibiting palmitylcarnitine oxidation. Mitochondrial NADH/NAD+ ratios were correlated positively with suppression of beta oxidation. The degree of suppression of beta oxidation by the malate-aspartate shuttle (NADH oxidation) or by succinate oxidation was dependent on the respiratory state. Both substrates extensively reduced mitochondrial NAD+ and markedly suppressed beta oxidation as respiration approached State 4. Calculations of the rates of flux of hydrogen equivalents through beta oxidation show that the suppression of beta oxidation by glutamate or by the malate-aspartate shuttle is accounted for by increased flux of reducing equivalents through mitochondrial malic dehydrogenase. This increased Flux is accompanied by an increase in the steady state NADH/NAD+ ratio and a marked decrease in the synthesis of citrate. The alpha-glycerophosphate shuttle was reconstituted with mitochondria isolated from rats treated with L-thyroxine. This shuttle was about equal to the reconstructed malate-aspartate shuttle in supression of palmitylcarnitine oxidation. This interaction could not be demonstrated in euthyroid animals owing to the low activity of the mitochondrial alpha-glycerol phosphate dehydrogenase. It is concluded that beta oxidation can be regulated by the NADH/NAD+ ratio. The observed stimulation of flux through malate dehydrogenase both by glutamate and by the malate-aspartate shuttle results in an increased steady state NADH/NAD+ ratio, and is linked to a stoichiometric outward transport of aspartate. We suggest, therefore, that some of the reducing pressure exerted by the malate-aspartate shuttle and by glutamate plus malate is provided through the energy-linked, electrogenic transport of aspartate out of the mitochondria. These results are discussed with respect to the mechanism of the genesis of ethanol-induced fatty liver.
...
PMID:Suppression of the mitochondrial oxidation of (-)-palmitylcarnitine by the malate-aspartate and alpha-glycerophosphate shuttles. 124 72

We describe an enzymatic method, requiring only 10 mul of serum, for determining CO2 as bicarbonate or dissolved gas. Phosphoenolpyruvate carboxylase catalyzes the reaction of HCO3- with phosphoenolypyruvate to give oxalacetate. The resulting NADH, in the presence of malate dehydrogenase, is oxidized to NAD+, and the decrease in absorbance at 340 nm is directly proportional to the amount of CO2 present in the sample. Reaction is complete in 3 to 6 min under assay conditions, and is linearly related to CO2 concentrations between 8 and 65 mmol/liter. Analytical recovery is 95-110% (average, 101%). Two laboratories compared values obtained by continuous-flow analysis. The resulting correlation coefficients were 0.966 and 0.987, values for the t-test were t(paired) equals 0.473 and t(paired) equals 0.334, and average day-to-day precisions (three concentrations) were 3.9% and 4.2%.
...
PMID:Enzymatic method for determination of CO2 in serum. 124 28


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

---