The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Paul A. Srere - One of the best experts on this subject based on the ideXlab platform.
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interaction between citrate synthase and Malate Dehydrogenase substrate channeling of oxaloacetate
Journal of Biological Chemistry, 1998Co-Authors: Igor Morgunov, Paul A. SrereAbstract:Abstract The interactions between pig heart citrate synthase and mitochondrial Malate Dehydrogenase or cytosolic Malate Dehydrogenase were studied using the frontal analysis method of gel filtration and by precipitation in polyethylene glycol. This method showed that an interaction between citrate synthase and mitochondrial Malate Dehydrogenase occurred but no interaction between citrate synthase and cytosolic Malate Dehydrogenase. Channeling of oxaloacetate in the Malate Dehydrogenase and citrate synthase-coupled systems was tested using polyethylene glycol precipitates of citrate synthase and mitochondrial Malate Dehydrogenase, and citrate synthase and cytosolic Malate Dehydrogenase. The effectiveness of large amounts of aspartate aminotransferase and oxaloacetate decarboxylase, as competing enzymes for the intermediate oxaloacetate, was examined. Aspartate aminotransferase and oxaloacetate decarboxylase were less effective competitors for oxaloacetate when precipitated citrate synthase and mitochondrial Malate Dehydrogenase in polyethylene glycol was used at low ionic strength compared with free enzymes in the absence of polyethylene glycol or with a co-precipitate of citrate synthase and cytosolic Malate Dehydrogenase. Substrate channeling of oxaloacetate with citrate synthase-mitochondrial Malate Dehydrogenase precipitate was inefficient at high ionic strength. These effects could be explained through electrostatic interactions of mitochondrial but not cytosolic Malate Dehydrogenase with citrate synthase.
Myroslawa Miginiac-maslow - One of the best experts on this subject based on the ideXlab platform.
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Transferring redox regulation properties from sorghum NADP-Malate Dehydrogenase to Thermus NAD-Malate Dehydrogenase.
Photosynthesis research, 2006Co-Authors: Emmanuelle Issakidis-bourguet, Danièle Lavergne, Xavier Trivelli, Paulette Decottignies, Myroslawa Miginiac-maslowAbstract:NADP-dependent chloroplastic Malate Dehydrogenase (E.C.1.1.1.82) is regulated by thiol disulfide-interchange with thioredoxin. It displays two regulatory disulfides per subunit, located in specific sequence extensions respectively at the N- and C-terminal ends of each subunit. In the present study, attempts were made to transfer the regulatory properties of sorghum NADP-Malate Dehydrogenase to a constitutively active NAD-dependent Malate dehydogenase (E.C.1.1.1.37) from the thermophilic bacteria Thermus flavus, by grafting the regulatory extensions of the former to the latter. The results demonstrate that a successful transfer of redox regulation properties requires the grafting of both full-length extensions, but also the introduction of specific hydrophobic residues in the core part of the protein. These residues are very likely involved in the interaction between monomers, and structural changes at the active site.
Željko Vučinić - One of the best experts on this subject based on the ideXlab platform.
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Cell wall-associated Malate Dehydrogenase activity from maize roots
Plant science : an international journal of experimental plant biology, 2011Co-Authors: Vesna Hadži-tašković Šukalović, Mirjana Vuletić, Ksenija Markovic, Željko VučinićAbstract:Isolated cell walls from maize (Zea mays L.) roots exhibited ionically and covalently bound NAD-specific Malate Dehydrogenase activity. The enzyme catalyses a rapid reduction of oxaloacetate and much slower oxidation of Malate. The kinetic and regulatory properties of the cell wall enzyme solubilized with 1M NaCl were different from those published for soluble, mitochondrial or plasma membrane Malate Dehydrogenase with respect to their ATP, Pi, and pH dependence. Isoelectric focusing of ionically-bound proteins and specific staining for Malate Dehydrogenase revealed characteristic isoforms present in cell wall isolate, different from those present in plasma membranes and crude homogenate. Much greater activity of cell wall-associated Malate Dehydrogenase was detected in the intensively growing lateral roots compared to primary root with decreased growth rates. Presence of Zn(2+) and Cu(2+) in the assay medium inhibited the activity of the wall-associated Malate Dehydrogenase. Exposure of maize plants to excess concentrations of Zn(2+) and Cu(2+) in the hydroponic solution inhibited lateral root growth, decreased Malate Dehydrogenase activity and changed isoform profiles. The results presented show that cell wall Malate Dehydrogenase is truly a wall-bound enzyme, and not an artefact of cytoplasmic contamination, involved in the developmental processes, and detoxification of heavy metals.
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PLASMA-MEMBRANE-BOUND Malate Dehydrogenase ACTIVITY IN MAIZE ROOTS
Protoplasma, 1999Co-Authors: V. Hadži-taskovišković, Mirjana Vuletić, D. Ignjatović-micić, Željko VučinićAbstract:Plasma membranes were isolated and purified from 14-day-old maize roots (Zea mays L.) by two-phase partitioning at a 6.5% polymer concentration, and compared to isolated mitochondria, microsomes, and soluble fraction. Marker enzyme analysis demonstrated that the plasma membranes were devoid of cytoplasmic, mitochondrial, tonoplast, and endoplasmic-reticulum contaminations. Isolated plasma membranes exhibited Malate Dehydrogenase activity, catalyzing NADH-dependent reduction of oxaloacetate as well as NAD+-dependent Malate oxidation. Malate Dehydrogenase activity was resistant to osmotic shock, freeze-thaw treatment, and salt washing and stimulated by solubilization with Triton X-100, indicating that the enzyme is tightly bound to the plasma membrane. Malate Dehydrogenase activity was highly specific to NAD+ and NADH. The enzyme exhibited a high degree of latency in both right-side-out (80%) and inside-out (70%) vesicle preparations. Kinetic and regulatory properties with ATP and Pi, as well as pH dependence of plasma-membrane-bound Malate Dehydrogenase were different from mitochondrial and soluble Malate Dehydrogenases. Starch gel electrophoresis revealed a characteristic isozyme form present in the plasma membrane isolate, but not present in the soluble, mitochondrial, and microsomal fractions. The results presented show that purified plasma membranes isolated from maize roots contain a tightly associated Malate Dehydrogenase, having properties different from mitochondrial and soluble Malate Dehydrogenases.
Leonard J. Banaszak - One of the best experts on this subject based on the ideXlab platform.
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crystal structure of escherichia coli Malate Dehydrogenase a complex of the apoenzyme and citrate at 1 87 a resolution
Journal of Molecular Biology, 1992Co-Authors: Michael D Hall, David G Levitt, Leonard J. BanaszakAbstract:The crystal structure of Malate Dehydrogenase from Escherichia coli has been determined with a resulting R-factor of 0.187 for X-ray data from 8.0 to 1.87 A. Molecular replacement, using the partially refined structure of porcine mitochondrial Malate Dehydrogenase as a probe, provided initial phases. The structure of this prokaryotic enzyme is closely homologous with the mitochondrial enzyme but somewhat less similar to cytosolic Malate Dehydrogenase from eukaryotes. However, all three enzymes are dimeric and form the subunit-subunit interface through similar surface regions. A citrate ion, found in the active site, helps define the residues involved in substrate binding and catalysis. Two arginine residues, R81 and R153, interacting with the citrate are believed to confer substrate specificity. The hydroxyl of the citrate is hydrogen-bonded to a histidine, H177, and similar interactions could be assigned to a bound Malate or oxaloacetate. Histidine 177 is also hydrogen-bonded to an aspartate, D150, to form a classic His.Asp pair. Studies of the active site cavity indicate that the bound citrate would occupy part of the site needed for the coenzyme. In a model building study, the cofactor, NAD, was placed into the coenzyme site which exists when the citrate was converted to Malate and crystallographic water molecules removed. This hypothetical model of a ternary complex was energy minimized for comparison with the structure of the binary complex of porcine cytosolic Malate Dehydrogenase. Many residues involved in cofactor binding in the minimized E. coli Malate Dehydrogenase structure are homologous to coenzyme binding residues in cytosolic Malate Dehydrogenase. In the energy minimized structure of the ternary complex, the C-4 atom of NAD is in van der Waals' contact with the C-3 atom of the Malate. A catalytic cycle involves hydride transfer between these two atoms.
Igor Morgunov - One of the best experts on this subject based on the ideXlab platform.
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interaction between citrate synthase and Malate Dehydrogenase substrate channeling of oxaloacetate
Journal of Biological Chemistry, 1998Co-Authors: Igor Morgunov, Paul A. SrereAbstract:Abstract The interactions between pig heart citrate synthase and mitochondrial Malate Dehydrogenase or cytosolic Malate Dehydrogenase were studied using the frontal analysis method of gel filtration and by precipitation in polyethylene glycol. This method showed that an interaction between citrate synthase and mitochondrial Malate Dehydrogenase occurred but no interaction between citrate synthase and cytosolic Malate Dehydrogenase. Channeling of oxaloacetate in the Malate Dehydrogenase and citrate synthase-coupled systems was tested using polyethylene glycol precipitates of citrate synthase and mitochondrial Malate Dehydrogenase, and citrate synthase and cytosolic Malate Dehydrogenase. The effectiveness of large amounts of aspartate aminotransferase and oxaloacetate decarboxylase, as competing enzymes for the intermediate oxaloacetate, was examined. Aspartate aminotransferase and oxaloacetate decarboxylase were less effective competitors for oxaloacetate when precipitated citrate synthase and mitochondrial Malate Dehydrogenase in polyethylene glycol was used at low ionic strength compared with free enzymes in the absence of polyethylene glycol or with a co-precipitate of citrate synthase and cytosolic Malate Dehydrogenase. Substrate channeling of oxaloacetate with citrate synthase-mitochondrial Malate Dehydrogenase precipitate was inefficient at high ionic strength. These effects could be explained through electrostatic interactions of mitochondrial but not cytosolic Malate Dehydrogenase with citrate synthase.