Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.1.1.37 (malate dehydrogenase)
 4,591 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Repeated injections of rat with 1-thyroxine (50 microgram/kg daily for 5 five-day weeks) retarded the weight gain of the animals and increased the absolute and relative size of the heart, adrenals and interscapular brown adipose tissue. In the myocardium and thigh muscle, thyroxine treatment resulted in elevated activity of oxidative enzymes, succinate dehydrogenase, malate dehydrogenase and citrate synthase, while the activities of glycolytic enzymes remained unchanged. Glycogen content of the heart was decreased following thyroxine regime. In the brown fat, on the other hand, thyroxine injections resulted in a reduction of the activity of oxidative enzymes. This reduction can be accounted for by the decreased protein (enzyme) content of the tissue due to deposition of fat. Furthermore, thyroxine treatment delayed the body cooling of the rats swimming in water at 25 degrees C and enhanced hyperthermic response to injected noradrenaline. All these changes, which were not observable in rats treated with daily alprenolol (20 mg/kg) injections, were as pronounced in rats injected with alprenolol together with thyroxine as in rats injected with thyroxine only. It is concluded that beta blockers do not antagonize the metabolic changes due to hyperthyroidism.
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PMID:Alprenolol fails to antagonize the metabolic changes following repeated thyroxine injections in the rat. 2 61

Gramicidin S is sorbed on the isolated membranes of granicidin-sensitive Micrococcus lysodeikticus strain. The antibiotic inhibits the membrane malate dehydrogenase within the temperature range of 9--42 degrees C, i.e. under conditions of gel and liquid-crystalline lipid state; however its effect at 10 degrees C is 10 times as low as is observed at 42 degrees C. The inhibitory effect of gramicidin S on malate dehydrogenase can be eliminated and the antibiotic can be removed from the membrane by an excess of different phospholipids. No transfer of the membrane components on exogenous phospholipids is observed. A prolonged (about 2 hrs, 30 degrees C) incubation of the membranes with gramicidin S results in irreversible inactivation of malate dehydrogenase, although the antibiotic can be still eliminated by an addition of phospholipid emulsions. It is suggested that gramicidin S forms complexes with phospholipids, in which the antibiotic is oriented to water. These complexes disturb the lipid-protein interactions, resulting in relaxation of the binding between the boundary phospholipids and proteins, in the loosening of near-protein lipid zones and simultaneous condensation of acid phospholipids in the whole membrane. Destruction of the lipid zone is accompanied by changes in the enzyme activity, by separation of lipid and protein regions and by transphase enzyme transitions (expulsion or immersion). A slow formation of secondary protein-protein associates may be irreversible.
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PMID:[Compartmentation of gramicidin 5 in membranes of sensitive bacteria and protein-lipid interactions]. 8 65

1. Cataract formation in streptozotocin-induced diabetes in rats was reduced by approximately 85% when a diet rich in maize oil (300 g/kg diet) (fat diet) was given, thus confirming results of earlier studies. However, the concentration of sorbitol in the lens of diabetic animals remained high, the values for diabetic rats given the standard diet and the fat died being 65 and 40 mumol/g protein respectively. 2. With the standard diet, the fatty acid profile of the triglycerides of the epididymal fat pads was characterized by a greater relative proportion of saturated fatty acids for the diabetic animals compared to that for the normal animals. The fat diet moderated the tendency towards saturation in the diabetic animals. 3. The fat diet had other effects on the diabetic animals; these included a reduced mortality rate, increased body-weight, a decrease in the daily water intake, and in the daily urinary excretion of glucose and urea. 4. In the diabetic animals the fat diet had no effect on the specific activities in the liver of hexokinase (EC 2.7.1.1), glucokinase (EC 2.7.1.2), phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40). However, the specific activity of glucose-6-phosphatase (EC 3.1.3.9) was reduced, while that of malate dehydrogenase (decarboxylating) (NADP) (EC 1.1.1.40) was increased. The NAD+:NADH ratio, as calculated from liver pyruvate and lactate concentrations, tended to increase. 5. The results suggested that the fat diet moderated the long-term metabolic effects of diabetes.
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PMID:The effect of an unsaturated-fat diet on cataract formation in streptozotocin-induced diabetic rats. 13 11

1. Oxalacetase from Asperigillus niger was found to be an inducible enzyme, the induction being dependent not only on neutralisation of the acidic growth medium but also on the presence of carbonate. An explanation is proposed. 2. Three methods were established for the quantitative determination of oxalacetase activity. These are based on the determination of the product acetate, on the absorbance of oxaloacetate and on coupling the hydrolysis of oxaloacetate to the oxidation of malate by NAD in the presence of malate dehydrogenase. 3. Oxalacetase was purified about 50-fold from cell-free extracts of A. niger and used to determine some of its properties such as kinetic constants. 4. 2S-[U-14C, 3-2H2] Malate in the presence of oxalacetase, NAD and malate dehydrogenase was partially converted to acetate and oxalate. The 3H/14C ratio of the isolated acetate was nearly twice as high as that of the malate used initially. The result demonstrates that the keto form of oxaloacetate, not the enol, is the substrate of the enzyme. 5. Equimolecular mixtures of 2S, 3S-[3-2H1] malate + 2S-[2-2H1] malate (mixture 1) and 2S, 3R-[3-2H1, 3H1] malate + 2S, 3R-[2-2H1, 3-3H1] malate (mixture 2) were prepared from 2S-[3-3H2] malate by incubation with fumarase in normal and tritiated water, respectively. The isolated mixture 1, in the presence of oxalacetase, NAD and malate dehydrogenase was incubated in tritiated water for formation of acetate and oxalate; the isolated mixture 2 was treated likewise in normal water. 6. The mixtures of symmetrically labelled [3H1] acetate and chiral acetates thus produced were isolated and the configuration of the [3H1, 3H1] acetate specimens was determined in the sequence acetate leads to malate leads to fumarate, as usual. The [2H1, 3H1] acetate derived from 2S, 3S-[3-2H1] malate (present in mixture 1( yielded a malate which on incubation with fumarase retained 65.0% of its total tritium content. This chiral acetate, therefore, had the R configuration. The [2H1, 3H1] acetate derived from 2S, 3R-[2-2H1, 3-3H1] malate produced a malate which retained 35% of its total tritium content, and therefore had the S configuration. 7. It was concluded that the detachment of the oxaloyl residue from oxaloacetate and its replacement by a proton proceed with inversion of configuration at the methylene group which becomes methyl during the hydrolysis.
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PMID:Partial purification and some properties of oxalacetase from Aspergillus niger. 17 20

This investigation was undertaken to further delineate the subcellular manifestations of arsenic toxicity following chronic exposure using combined ultrastructural and biochemical techniques. Male rats were given access to deionized drinking water solutions containing 0, 20, 40, or 85 arsenic as arsenate (As(+5)) for 6 weeks. In situ swelling of liver mitochondria was the most prominent ultrastructural change observed. Mitochondrial respiration studies indicated decreased state 3 respiration and respiratory control ratios (RCR) for pyruvate/malate but not succinate mediated respiration. Specific activity of monoamine oxidase which is localized on the outer mitochondrial membrane showed increases of up to 150% of control and cytochrome-C oxidase which is localized on the inner mitochondrial membrane showed increases in specific activity of 150-200%. Activity of malate dehydrogenase which is localized in the mitochondrial matrix was unchanged at any dose level. These studies indicate that decreased mitochondrial respiration is only one aspect of arsenic toxicity to this organelle. Marked arsenic-mediated perturbation of important enzyme systems localized in mitochondria which participate in the control of respiration and other normal mitochondrial functions are also important manifestations of cellular dysfunction.
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PMID:Ultrastructural and biochemical effects of prolonged oral arsenic exposure on liver mitochondria of rats. 19 4

Exposure to drinking water containing as much as 500 ppm aluminum chloride for periods of 30, 60, and 90 days had no apparent effect on male reproductive processes. In an attempt to correlate enzyme activity with particular spermatogenic cell types, postnatal development of testicular enzymes was studied. Eight enzymes were selected: hyaluronidase (H), lactate dehydrogenase isoenzyme-X (LDH-X), dehydrogenases of sorbitol (SDH), alpha-glycerophosphate (GPDH), glucose-6-phosphate (G6PDH), malate (MDH), glyceraldehyde-3-phosphate (G3PDH), and isocitrate (ICDH). Enzyme specific activities in testicular homogenates were determined. Two types of enzyme developmental patterns were observed. One was represented by H, LDH-X, SDH, and GPDH; and the other by G6PDH, MDH, G3PDH, and ICDH. The former was characterized by a change in enzyme activities from low in newborn to high in adult while in the latter this pattern was reversed. The two complementary enzyme systems crossed each other at puberty. Prior to puberty, only spermatogonial cells are present; sperm differentiation initiated at puberty adds spermatocytes and spermatids to the testicular cell population. Male rats were exposed to borax in their diet for periods of 30 and 60 days. Concentrations of boron were 0, 500, 1000, and 2000 ppm. At the end of each experimental period, the specific activities of the selected enzymes were determined in the testis and prostate. Correlations of enzyme activity with testicular histology and androgen activities of the male accessory organs were sought. In addition, plasma FSH, LH, and testosterone levels were measured to assess pituitary-testicular interaction. Plasma and testicular boron concentrations were determined and a minimum boron concentration which induced germinal aplasia and male infertility was estimated. In both 30 and 60 day feeding studies, male rats receiving 500 ppm failed to demonstrate any significant adverse effects. In contrast, male rats receiving 100 and 2000 ppm boron displayed a significant loss of germinal elements, although most of the Leydig and Sertoli cells appeared normal. Testicular atrophy was associated with a decrease in seminiferous tubular diameter and a marked reduction of spermatocytes and spermatogenic cells. These morphologic alterations were associated with a concomitant reduction of H, SDH, and LDH-X specific activities. In contrast, the specific activities of G3PDH and MDH were significantly elevated above control. The increase in these enzyme activities can be attributed to the relative enrichment of spermatogonial cells during the loss of spermatocytes and spermiogenic cells. Boron-induced male germinal aplasia was also associated with significantly elevated plasma FSH while plasma LH and testosterone levels were not significantly altered. Plasma testosterone levels were unaltered. Male fertility studies demonstrated that at the 500 ppm boron level, fertility was unaffected. However, at 1000 and 2000 ppm boron, male fertility was significantly reduced. Most effects were reversible within 5 weeks. However, the male group receiving 2000 ppm boron for 60 days remained sterile. There was no dose-related decrease in litter size or fetal death in utero. Therefore, the boron-induced infertility was apparently not due to a dominant lethal effect but rather to germinal aplasia. Boron appears toxic to spermatogenic cells at testicular concentrations of 6-8 ppm.
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PMID:Assessment of environmental factors affecting male fertility. 44 58

The purification procedure reported includes fractionation of water extract from chicken hearts with ammonium sulfate, fractional precipitation with ethanol, chromatography on Whatman CM-52 cellulose and crystallization. Specific activity of the pure crystalline enzyme was 234 micromoles.min-1.mg-1, as determined in the coupled assay with malate dehydrogenase (pH 7.5; 25 degrees). The amino acid composition of the enzyme was determined and the circular dichroism spectrum was recorded in the 200-250 nm range. The spectrum shows two negative bands with extrema at 208 and 220 nm. From the circular dichroism data it is estimated that aspartate transaminase contains approximately 40% alpha-helix and 10% beta-structure.
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PMID:[Improved procedure for purification of aspartate transaminase from chicken heart cytosol. Characterization of the enzyme]. 73 31

Malate dehydrogenase, reputed to be a soluble matricial enzyme, is shown to be also strongly associated with the inner membrane, in pig heart mitochondria. Repeated sonications, water washes, freezing-thawing cycles are not very effective to remove malate dehydrogenase activity from inner membranes, which whatever the treatment, remains important. This activity is only partly solubilized by the substrates, malate or oxaloacetate. High ionic strength treatments by either NaCl-carbonate or 3M KCl have a strong effect, but they also remove cytochrome c oxidase and rotenone-sensitive NADH-cytochrome c reductase, reputed inner membrane intrinsic enzymes, thus strongly damaging the inner membrane. After the action of phospholipase A from Naja Naja Venom, the residual activity is about twenty per cent and only phosphatidyl choline and phosphatidyl ethanolamine decreased significantly, the other phospholipids being unchanged. It is suggested that the enzyme is deeply buried in the membrane and mainly interacts with phosphatidyl choline.
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PMID:The markers of pig heart mitochondrial sub-fractions. II. - On the association of malate dehydrogenase with inner membrane. 75 79

Setaria cervi, the filarial parasite inhabiting the Indian water buffalo (Bubalus bubalis Linn.) contained almost all the enzymes involved in glycogen degradation. Significant activities of glycogen phosphorylase, glucokinase, phosphoglucomutase, phosphoglucose isomerase, phosphofructokinase, FDP-aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate hydratase, pyruvate kinase, lactate dehydrogenase glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were detected in cell-free extracts of whole worms. The presence of PEP-carboxykinase, malate dehydrogenase, fumarase and fumarate reductase revealed the functioning of the PEP-succinate pathway in addition to phosphorylating glycolysis and pentose phosphate pathway in the parasite. Excepting fumarate reductase all other enzymes were localized in the particulate-free cytosol fraction, although small amounts of glycogen phosphorylase, aldolase and lactate dehydrogenase were also detected in the mitochondrial fraction.
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PMID:Setaria cervi: enzymes of glycolysis and PEP-succinate pathway. 86 May 72

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.
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PMID:Enzymatic activity of pig heart mitochondrial malate dehydrogenase monomolecular films by surface exchange technique. 87 77


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