Purification and characterization of an NAD-dependent malate dehydrogenase from leaves of the crassulacean acid metabolism plant Aptenia cordifolia |
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| Affiliation: | 1. Department of Computer Science and Artificial Intelligence, CITIC-UGR (Research Center on Information and Communications Technology), University of Granada, 18071 Granada, Spain;2. Department of Aerospace Engineering, The Pennsylvania State University, University Park, 16802 PA, United States;3. Department of Computer Science, University of Oviedo, 33204 Gijón, Spain;1. Institute of Plant Physiology of Russian Academy of Sciences, Botanicheskaya str. 35, Moscow 127276, Russia;2. INRA Montpellier SupAgro, F-34060 Montpellier, Cedex 2, France;1. Institute of Process Engineering in Life Sciences, Section II: Technical Biology, Karlsruhe Institute of Technology (KIT), Engler-Bunte-Ring 1, 76131 Karlsruhe, Germany;2. Institute of Food Science and Biotechnology, Section Bioprocess Engineering (150k), University of Hohenheim, Garbenstr. 25, 70599 Stuttgart, Germany;1. Institute of Chemical Technology and Engineering, Faculty of Chemical Technology, Poznan University of Technology, Berdychowo 4, 60965 Poznan, Poland;2. Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60179 Poznan, Poland;3. Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50422 Wroclaw, Poland;4. European Centre for Bioinformatics and Genomics, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61704 Poznan, Poland;1. Embrapa Agrossilvipastoril, Sinop, MT, Brazil;2. Universidade Federal de Mato Grosso, Sinop, MT, Brazil;3. Embrapa Milho e Sorgo, Sete Lagoas, MG, Brazil;4. Embrapa Florestas, Colombo, PR, Brazil;5. Universidade do Estado de Mato Grosso, Cáceres, MT, Brazil;6. Universidade Federal de Mato Grosso do Sul, Chapadão do Sul, MS, Brazil |
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| Abstract: | An NAD-malate dehydrogenase (NAD-MDH, EC 1.1.1.37) was purified and characterized from leaves of Aptenia cordifolia L. f. (Schwant). This plant performs crassulacean acid metabolism (CAM), as indicated by: (a) elevated levels of phosphoenolpyruvate carboxylase (PEPC) and NAD(P) malic enzyme; (b) regulation of PEPC compatible with its function during the night; (c) characteristic day/night changes in titratable acidity; and (d) gas exchange profile consistent with that shown by CAM plants. These features remained unchanged by water availability or salt stress, suggesting constitutive CAM. The purified MDH showed a subunit molecular mass of 39.4 kDa, a native mass of 83 kDa (dimer) and a pI of 5.8. It cross-reacted with antibodies against cytosolic malate dehydrogenase (cMDH) from pineapple. Maximum activities for oxaloacetate (OAA) reduction or malate oxidation were observed at pH 7.0 and between pH 7.2 and 8.4, respectively. The enzyme was inhibited by excess OAA, in a pH-dependent manner. A discontinuity was observed in Arrhenius plots at 33 °C, with an activation energy twice as high below this temperature. Although immunologically related, some physical and kinetic dissimilarities between the A. cordifolia and pineapple enzymes suggest that diverse CAM metabolic subtypes may require different MDH isozymes to carry out OAA reduction. |
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