Malate Metabolism by Desulfovibrio gigas and its Link to Sulfate and Fumarate Reduction: Purification of the Malic Enzyme and Detection of NAD(P)+ Transhydrogenase Activity

ABSTRACTLactobacillus caseiis the only lactic acid bacterium in which two pathways forl-malate degradation have been described: the malolactic enzyme (MLE) and the malic enzyme (ME) pathways. Whereas the ME pathway enablesL. caseito grow onl-malate, MLE does not support growth. Themlegene cluster consists of three genes encoding MLE (mleS), the putativel-malate transporter MleT, and the putative regulator MleR. Themaegene cluster consists of four genes encoding ME (maeE), the putative transporter MaeP, and the two-component system MaeKR. Since both pathways compete for the same substrate, we sought to determine whether they are coordinately regulated and their role inl-malate utilization as a carbon source. Transcriptional analyses revealed that themleandmaegenes are independently regulated and showed that MleR acts as an activator and requires internalization ofl-malate to induce the expression ofmlegenes. Notwithstanding, bothl-malate transporters were required for maximall-malate uptake, although only anmleTmutation caused a growth defect onl-malate, indicating its crucial role inl-malate metabolism. However, inactivation of MLE resulted in higher growth rates and higher final optical densities onl-malate. The limited growth onl-malate of the wild-type strain was correlated to a rapid degradation of the availablel-malate tol-lactate, which cannot be further metabolized. Taken together, our results indicate thatL. caseil-malate metabolism is not optimized for utilization ofl-malate as a carbon source but for deacidification of the medium by conversion ofl-malate intol-lactate via MLE.

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Effect of NAD and Rotenone on the Partitioning of Malate Oxidation Between Malate Dehydrogenase and Malic Enzyme in Isolated Plant Mitochondria

Functional Plant Biology ◽

10.1071/pp9850229 ◽

1985 ◽

Vol 12 (3) ◽

pp. 229 ◽

Cited By ~ 4

Author(s):

JH Bryce ◽

JT Wiskich

Keyword(s):

Energy Metabolism ◽

Electron Transport ◽

Oxygen Uptake ◽

Malate Dehydrogenase ◽

Malic Enzyme ◽

Plant Mitochondria ◽

Metabolizing Enzyme ◽

Stimulation Of ◽

Malate Metabolism ◽

Malate Oxidation

Our aim was to determine whether there is a specific link between NAD-malic enzyme and the rotenone- insensitive bypass of electron transport. Mitochondria were isolated from fresh beetroot tissue, aged beetroot slices, and turnips. Oxygen uptake and pyruvate production were measured in reactions where these mitochondria were metabolizing malate at pH 6.8 in the presence of glutamate, to facilitate the removal of oxaloacetate, and in its absence. In the absence of glutamate there was substantial activity of malic enzyme. NAD+ (577 �M) prevented a fall in oxygen uptake by stimulating malic enzyme. Rotenone (19 �M) reduced oxygen uptake. This inhibited rate was stimulated by NAD+ due, in particular, to a stimulation of malic enzyme. We conclude that the stimulation of malate metabolism by NAD+ is accounted for by malic enzyme due to the unfavourable equilibrium of malate dehydrogenase for malate oxidation and the resultant accumulation of oxaloacetate, and not to any specific link between malic enzyme and the rotenone-insensitive bypass. In the presence of glutamate, malate dehydrogenase was the predominant malate metabolizing enzyme. Oxygen uptake and malic enzyme were stimulated and inhibited by NAD+ and rotenone, respectively. In the presence of rotenone, NAD+ stimulated oxygen uptake and increased the percentage due to malic enzyme. This stimulation is accounted for by the higher Kin of the rotenone-insensitive dehydrogenase for NADH and the unfavourable equilibrium position of malate dehydrogenase resulting in activation of malic enzyme only. We conclude that malic enzyme is not specifically linked to the rotenone-insensitive pathway of electron transport. This has important implications for the regulation of energy metabolism in plants.

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The localization of nitrite reductase, glutamate synthase and malate metabolism enzymes in Pisum arvense L. roots

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.1985.008 ◽

2014 ◽

Vol 54 (1) ◽

pp. 85-93

Author(s):

Genowefa Kubik-Dobosz ◽

Grażyna Kłobus

Keyword(s):

Nitrite Reductase ◽

Malic Enzyme ◽

Acid Metabolism ◽

Glutamate Synthase ◽

Sucrose Density Gradient ◽

Pyridine Nucleotides ◽

Pisum Arvense ◽

Metabolism Enzymes ◽

Malic Enzyme Activity ◽

Malate Metabolism

Centrifugation of a homogenate made from <em>Pisum arvense</em> L. roots in a sucrose density gradient enabled the separation of the plastid fraction from mitochondria and microsomes. The presence of nitrite reductase and glutamate synthase was demonstrated in the plastids. Malic enzyme activity was not linked with any organelle fraction and was found only in the cytosol. High malate dehydrogenase activity was found in the mitochondria fraction, although its activity was also determined in plastids. The results suggest that malic acid metabolism in plastids may be the source of reduced pyridine nucleotides for reactions catalysed by nitrite reductase and glutamate synthase.

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Enzymes of malate metabolism inMesorhizobium ciceriCC 1192

Canadian Journal of Microbiology ◽

10.1139/w02-021 ◽

2002 ◽

Vol 48 (4) ◽

pp. 279-284

Author(s):

Catherine Ann Tabrett ◽

Les Copeland

Keyword(s):

Malate Dehydrogenase ◽

Malic Enzyme ◽

Symbiotic Nitrogen Fixation ◽

Kinetic Studies ◽

The Other ◽

Nitrogen Fixing ◽

Multiple Forms ◽

Free Living ◽

Mesorhizobium Ciceri ◽

Malate Metabolism

Electrophoretic studies were performed on enzymes concerned with the oxidation of malate in free-living and bacteroid cells of Mesorhizobium ciceri CC 1192, which forms nitrogen-fixing symbioses with chickpea (Cicer arietinum L.) plants. Two malate dehydrogenases were detected in extracts from both types of cells in native polyacrylamide electrophoresis gels that were stained for enzyme activity. One band of malate dehydrogenase activity was stained only in the presence of NADP+, whereas the other band was revealed with NAD+but not NADP+. Further evidence for the occurrence of separate NAD- and NADP-dependent malate dehydrogenases was obtained from preliminary enzyme kinetic studies with crude extracts from free-living M. ciceri CC 1192 cells. Activity staining of electrophoretic gels also indicated the presence of two malic enzymes in free-living and bacteroid cells of M. ciceri CC 1192. One malic enzyme was active with both NAD+and NADP+, whereas the other was specific for NADP+. Possible roles of the multiple forms of malate dehydrogenase and malic enzyme in nitrogen-fixing symbioses are discussed.Key words: Mesorhizobium ciceri, malate dehydrogenase, malic enzyme, chickpea bacteroids, symbiotic nitrogen fixation.

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Gluconeogenesis in Plants: A Key Interface between Organic Acid/Amino Acid/Lipid and Sugar Metabolism

Molecules ◽

10.3390/molecules26175129 ◽

2021 ◽

Vol 26 (17) ◽

pp. 5129

Author(s):

Robert P. Walker ◽

Zhi-Hui Chen ◽

Franco Famiani

Keyword(s):

Enzyme Activity ◽

Malic Enzyme ◽

Krebs Cycle ◽

Cytosolic Ph ◽

Widespread Occurrence ◽

Nitrogenous Compounds ◽

Coordinate Regulation ◽

Fine Control ◽

Malate Metabolism

Gluconeogenesis is a key interface between organic acid/amino acid/lipid and sugar metabolism. The aims of this article are four-fold. First, to provide a concise overview of plant gluconeogenesis. Second, to emphasise the widespread occurrence of gluconeogenesis and its utilisation in diverse processes. Third, to stress the importance of the vacuolar storage and release of Krebs cycle acids/nitrogenous compounds, and of the role of gluconeogenesis and malic enzyme in this process. Fourth, to outline the contribution of fine control of enzyme activity to the coordinate-regulation of gluconeogenesis and malate metabolism, and the importance of cytosolic pH in this.

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Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111276 ◽

1984 ◽

Vol 42 ◽

pp. 232-233

Author(s):

S.M. Geyer ◽

C.L. Mendenhall ◽

J.T. Hung ◽

E.L. Cardell ◽

R.L. Drake ◽

...

Keyword(s):

Electron Microscopy ◽

Endoplasmic Reticulum ◽

Enzyme Activity ◽

Malic Enzyme ◽

Smooth Endoplasmic Reticulum ◽

Rat Hepatocytes ◽

Mature Male ◽

Treatment Groups ◽

Malic Enzyme Activity ◽

Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

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