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

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%.
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PMID:Enzymatic method for determination of CO2 in serum. 124 28

In vitro rates of lactate conversion to glucose and oxidation to CO2 were determined in livers of stress-susceptible (SS) and stress-resistant (SR) pigs because we hypothesized that livers of SS pigs had a lower capacity than livers of SR pigs to remove lactate from blood. Stress-susceptibility was determined by reaction to halothane at 7 weeks of age. At approximately 9 weeks of age, pigs were assigned to one of three experimental diets. Pigs weighing 95 kg were slaughtered immediately after stress, and liver samples were obtained. Incorporation of lactate into glucose in liver of SS pigs was 38% of that in SR pigs. Addition of either vitamin C or vitamins C and E plus magnesium oxide and collagen extract to a corn-soy diet did not alter lactate conversion to glucose, but depressed lactate oxidation to CO2. No differences were detected in either activities of lactate dehydrogenase, HAD-malate dehydrogenase, phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase, and glucose-6-phosphatase or concentration of glycogen in livers of SS and SR pigs. Our data indicate that livers of SS pigs possess a lower capacity to incorporate lactate into glucose and to oxidize lactate to CO2; maximal activities of enzymes measured in this study are not the cause of these differences. Reduced capacity of lactate metabolism in livers of SS pigs seems a part of the etiology of the porcine stress syndrome.
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PMID:Gluconeogenesis from lactate in liver of stress-susceptible and stress-resistant pigs. 126 79

The central glycolytic and oxidative pathways and the ATP-producing mechanisms differ in sane and malignant cells by their regulation and dynamics. Fast-growing, poorly-differentiated cancer cells characteristically show high aerobic glycolysis. In the same way, cholesterol biosynthesis, which occurs by normal pathways in tumors, is deficient in feed-back regulation and in sterol-transport mechanisms. Other metabolic ways are deficient, as for example, intramitochondrial aldehyde catabolism, at the origin of a possible acetaldehyde toxicity, which can be circumvented by the synthesis of an unusual and neutral product for mammalian cells acetoin, through tumoral pyruvate dehydrogenase. If most of the glycolytic pyruvate is deviated to lactate production, little of the remaining carbons enter a truncated Krebs cycle where citrate is preferentially extruded to the cytosol where it feeds sterol synthesis. Glutamine is the major oxidizable substrate by tumor cells. Inside the mitochondrion, it is deaminated to glutamate through a phosphate-dependent glutaminase. Glutamate is then preferentially transaminated to alpha-ketoglutarate that enters the Krebs cycle. Glutamine may be completely oxidized through the abnormal Krebs cycle only if a way of forming acetyl CoA is present: cytosolic malate entering mitochondria is preferentially oxidized to pyruvate + CO2 through an intramitochondrial NAD(P)(+)-malic enzyme, whereas intramitochondrial malate is preferentially oxidized to oxaloacetate through malate dehydrogenase, thus providing a high level of intramitochondrial substrate compartmentation. These and other regulatory aberrations in tumor cells appear to be reflections of a complex set of non-random phenotypic changes, initiated by expression of oncogenes.
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PMID:Deviant energetic metabolism of glycolytic cancer cells. 147 40

An enzymatic method for measuring total carbon dioxide content in freeze-clamped animal tissues is described. Total carbon dioxide content [TCO2] was defined as the sum of the dissolved CO2, the bicarbonate concentration, and the carbonate concentration. Tissue was extracted in 80% methanol, 20 mM 2-amino-2-methyl-1-propanol, pH 9.5 at 25 degrees C and homogenized in a 1.5-ml Sardstat screw-top test tube containing 0.5-mm glass beads and a minibead beater. Total CO2 was determined as bicarbonate/carbonate by monitoring the oxidation of NADH at 340 nm using the coupled assay of phosphoenolpyruvate carboxylase (EC 4.1.1.31) and malate dehydrogenase (EC 1.1.1.37). In the coupled assay system, 1 mumol of bicarbonate/carbonate consumed is equivalent to the oxidation of 1 mumol NADH at 340 nm. The assay medium comprised 50 mM 2-amino-2-methyl-1-propanol, pH 9.0 at 25 degrees C, 5 mM phosphoenolpyruvate (PEP), 0.25 mM NADH, 5 mM MgCl2, 5 mM mercaptoethanol, 0.02% bovine serum albumin, 10 mM oxamate, PEP carboxylase (0.5 units/ml), and malate dehydrogenase (0.5 units/ml). The total CO2 content measured in freeze-clamped rat heart, liver, brain, and skeletal muscle was 20.53 +/- 0.64, 17.34 +/- 0.67, 17.00 +/- 0.48, 16.06 +/- 0.53 mumol/g wet wt tissue, respectively (n = 5). The total CO2 in the crusher muscle of the lobster was found to be 5.0 +/- 0.33 mumol/g wet wt. Total CO2 was also enzymatically measured in arterial plasma from four chronically cannulated male wistar rats and was 24.65 +/- 1.81 mumol/ml plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Enzymatic determination of total CO2 in freeze-clamped animal tissues and plasma. 175 Jun 72

The effects of O2 and CO2 on the growth in culture of Trichomonas vaginalis strain C1-NIH were investigated. Growth under pre-purified N2 in the absence of CO2 supplementation gave a doubling time of 4.4 h; when traces of O2 (less than 0.25 microM) were present, the doubling time was 3.5 h. Organisms grew most rapidly (doubling time 2.3 h) with traces of O2 (less than 0.25 microM) and with the CO2 level controlled at 5 mM. The balance of fermentation products from maltose was greatly influenced by supplied gases. Under strictly anaerobic conditions at 5 mM CO2, equimolar glycerol and lactate accounted for more than 95% of the measured products, whereas lower CO2 increased acetate production. Under microaerobic conditions (O2 less than 0.25 microM) acetate was the major product when CO2 was limited to that evolved endogenously; again 5 mM CO2 favoured glycerol and lactate production. Activities of key enzymes measured in cell-free extracts (pyruvate:ferredoxin oxidoreductase, hydrogenase, glycerol kinase, malate dehydrogenase (decarboxylating) and lactate dehydrogenase) altered with growth conditions commensurately with observed changes in metabolic flux patterns. These results suggest that T. vaginalis is optimally adapted to conditions it experiences in situ in the vagina (traces of O2, high CO2).
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PMID:Trichomonas vaginalis requires traces of oxygen and high concentrations of carbon dioxide for optimal growth. 211 56

Malate dehydrogenase (NADP) (NADP-MDH) is an important enzyme of the photosynthetic CO2 fixation pathway of C4 plants. We have isolated two clones from a sorghum lambda gt11 cDNA library (CM3, 932 bp, and CM7, 1441 bp). Nucleotide sequence analysis of the cDNAs CM3 and CM7 showed the existence of two NADP-MDH mRNA species encoding different enzyme subunits. Microsequencing of the N-terminus of the mature protein indicated that a specific cleavage of 13 amino acids occurred during the purification steps of the enzyme. The full-length cDNA CM7 contains a large open reading frame encoding an NH2-terminal transit peptide of 40 amino acids and a mature protein of 389 amino acids (42.207 kDa). Alignment of the NADP-MDH sequence with those of several malate dehydrogenases revealed some similarities with NAD-MDHs.
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PMID:Primary structure of sorghum malate dehydrogenase (NADP) deduced from cDNA sequence. Homology with malate dehydrogenase (NAD). 220 86

Pyruvate orthophosphate dikinase, phosphoenolpyruvate carboxylase, and NADP-malate dehydrogenase function in a series of reactions for fixing CO2 in mesophyll cells and NADP-malic enzyme (ME) catalyzes the production of CO2 and NADPH in bundle sheath cells of maize which is a NADP-ME type C4 plant. Northern blot analyses with cDNA clones for pyruvate orthophosphate dikinase and phosphoenolpyruvate carboxylase and in vitro translation-immunoprecipitation experiments with antiserum to NADP-malate dehydrogenase showed that pools of transcripts of these three genes grow and shrink coordinately in mesophyll cells but not in bundle sheath cells upon illumination of dark-grown maize seedlings. Western blot analyses indicated that the protein levels of phosphoenolpyruvate carboxylase and pyruvate orthophosphate dikinase are low in dark-grown maize seedlings and increase progressively following light-induced transient accumulation of their mRNAs in mesophyll cells. These proteins continue to accumulate and plateau in late-greening and green leaves in spite of a rapid drop in the sizes of their mRNA pools. Surprisingly, relatively large amounts of NADP-malate dehydrogenase are present in mesophyll cells of etiolated leaves despite the low level of the corresponding mRNA. No phosphoenolpyruvate carboxylase or NADP-malate dehydrogenase were detected in bundle sheath cells. On the other hand, the ME gene responds to light induction at both the transcriptional and translational levels only in bundle sheath cells. Moreover, the steady-state level of ME mRNA stays high in late-greening and green leaves in contrast to the rapid decline of mRNA levels of three other C4 pathway genes in mesophyll cells. In addition, low levels of both the mRNA and protein encoded by the PPDK gene were detected in bundle sheath cells. These levels were not influenced by light as distinguished from the patterns observed in mesophyll cells.
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PMID:Differential expression of C4 pathway genes in mesophyll and bundle sheath cells of greening maize leaves. 244 51

Pyruvate-dependent CO2 fixation by isolated mitochondria was strongly inhibited by sodium benzoate. Pyruvate carboxylase was identified as a site of inhibition by limiting flux measurements to assays of pyruvate carboxylase coupled with malate dehydrogenase. Benzoate reduced pyruvate-dependent incorporation of [14C]KHCO3 into malate and pyruvate-dependent malate accumulation by 74 and 72%, respectively. Aspartate-dependent malate accumulation was insensitive to benzoate, ruling out malate dehydrogenase as a site of action. Inhibition by benzoate was antagonized by glycine, which sharply accelerated conversion of benzoate to hippurate. Assays of coenzyme A and its acyl derivatives revealed inhibition to correlate with depletion of acetyl CoA and accumulation of benzoyl CoA. Depletion of acetyl CoA was sufficient to account for greater than 50% reduction in pyruvate carboxylase activity. Competition between acetyl CoA and benzoyl CoA for the activator site on pyruvate carboxylase was insignificant. Results support the interpretation that the observed inhibition of pyruvate carboxylase occurred primarily by depletion of the activator, acetyl CoA, through sequestration of coenzyme A during benzoate metabolism.
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PMID:Inhibition of pyruvate carboxylase by sequestration of coenzyme A with sodium benzoate. 249 93

A major difference between the metabolism of Leishmania species amastigotes and cultured promastigotes was found in the area of CO2 fixation and phosphoenolpyruvate metabolism. Malate dehydrogenase (EC 1.1.1.37) and phosphoenolpyruvate carboxykinase (EC 4.1.1.49) were at much higher activities in amastigotes than promastigotes of both L. m. mexicana and L. donovani, whereas the reverse was true of pyruvate kinase (EC 2.7.1.40). Pyruvate carboxylase (EC 6.4.1.1) and malic enzyme (carboxylating) (EC 1.1.1.40) could not be detected in L. m. mexicana amastigotes. Promastigotes of L. m. mexicana had a high NAD-linked glutamate dehydrogenase activity in comparison to amastigotes, whereas NADP-linked glutamate dehydrogenase activity was detected only in amastigotes. Leishmania m. mexicana culture promastigotes were killed in vitro by the trivalent antimonial Triostam (LD50, 20 micrograms/ml) and the trivalent arsenical melarsen oxide (LD50, 20 micrograms/ml), but they were unaffected by Pentostam. Neither antimonial drug significantly inhibited leishmanial hexokinase (EC 2.7.1.2), phosphofructokinase (EC 2.7.1.11), pyruvate kinase, malate dehydrogenase or phosphoenolpyruvate carboxykinase, whereas melarsen oxide was a potent inhibitor of all the enzymes tested except phosphoenolpyruvate carboxykinase.
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PMID:Leishmania mexicana: enzyme activities of amastigotes and promastigotes and their inhibition by antimonials and arsenicals. 298 38

This work was performed to gain more information on the role of pyruvate kinase isoenzymes in the regulation of renal carbohydrate metabolism. Immunohistochemically, pyruvate kinase type L is shown to be localized in the proximal tubule of the nephron and pyruvate kinase type M2 in the distal tubule and the collecting duct. a tight relationship between gluconeogenesis and pyruvate recycling was found. The rate of gluconeogenesis (8 mumol/g wet wt. per 30 min) was of the same order of magnitude as the rate of pyruvate recycling (10.92 mumol/g wet wt. per 30 min). Stimulation of gluconeogenesis from 20 mM lactate in kidney cortex slices of 24-h-starved rats by dibutyryl-cAMP, alanine and parathyroid hormone was connected with a decrease in pyruvate recycling; inhibition of gluconeogenesis due to a lack of Ca2+ in the incubation medium was linked with an increase in pyruvate recycling. The degradation of [6-14C]glucose to lactate, pyruvate, ketone bodies and CO2 and of [2-14C]lactate was unaffected by dibutyryl-cAMP, alanine, epinephrine, vasopressin or the omission of Ca2+ from the incubation medium. 1 mM dibutyryl-cAMP or 5 mM alanine did not alter the activities of oxaloacetate decarboxylase, 'malic' enzyme and malate dehydrogenase from rat kidney cortex. Since aerobic glycolysis in the distal tubules and the collecting ducts is not influenced by hormones, dibutyryl-cAMP and Ca2+, pyruvate kinase type M2 residing in this tissue is unlikely to be a control point of glycolysis. Since this tissue degrades only one-seventh of the glucose formed via gluconeogenesis, it does not contribute significantly to pyruvate recycling. Therefore, the decrease of pyruvate recycling in the presence of dibutyryl-cAMP and alanine in rat kidney cortex slices, leading to increased renal gluconeogenesis, has to be ascribed to the regulation of pyruvate kinase type L.
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PMID:Localization and role of pyruvate kinase isoenzymes in the regulation of carbohydrate metabolism and pyruvate recycling in rat kidney cortex. 300 99


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