Malate oxaloacetate shuttle11/14/2023 ![]() This pathway spans the mitochondrial and cytoplasmic spaces, transferring reducing equivalents across the mitochondrial membrane. In this eukaryotic route of aspartate degradation, aspartate is converted to malate as part of the reversible malate-aspartate shuttle. Generation of Precursor Metabolites and Energy Planta, 224, 380–393.If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity. (Heynh.) plants under long‐ and short‐day conditions. (2006) Influence of the photoperiod on redox regulation and stress responses in Arabidopsis thaliana L. Plant Physiology, 153, 832–840.īecker B., Holtgrefe S., Jung S., Wunrau C., Kandlbinder A., Baier M., Dietz K.J., Backhausen J.E., Scheibe R. (2010) An autoinhibitory domain confers redox regulation to maize glycerate kinase. Photosynthesis Research, 64, 1–13.īartsch O., Mikkat S., Hagemann M., Bauwe H. (2000) Electron acceptors in isolated intact spinach chloroplasts act hierarchically to prevent over‐reduction and competition for electrons. Planta, 205, 359–366.īackhausen J.E., Kitzmann C., Horton P., Scheibe R. (1998) NAD‐dependent malate dehydrogenase and glyceraldehyde 3‐phosphate dehydrogenase isoenzymes play an important role in dark metabolism of various plastid types. ![]() Archives of Biochemistry and Biophysics, 324, 201–208.īackhausen J.E., Vetter S., Baalmann E., Kitzmann C., Scheibe R. (1995) Reductive modification and nonreductive activation of purified spinach chloroplast NADP‐dependent glyceraldehyde‐3‐phosphate dehydrogenase. Plant Biology published by John Wiley & Sons Ltd on behalf of German Society for Plant Sciences, Royal Dutch Botanical Society.īaalmann E., Backhausen J.E., Rak C., Vetter S., Scheibe R. This review updates the current knowledge on MDH isoforms and the shuttle systems for intercompartmental dicarboxylate exchange, focusing on the various metabolic functions of these valves.Įnergy supply malate dehydrogenase malate valve redox balance shuttling. Knockout mutants lacking the isoforms from chloroplasts, mitochondria and peroxisomes have been characterised, but not much is known about cytosolic NAD-MDH isoforms and their role in planta. While redox regulation of the main cytosolic MDH isoform has been shown, knowledge about regulation of the other two cytosolic MDHs as well as NAD-MDH isoforms from peroxisomes and mitochondria is still lacking. In contrast, the plastid NAD-MDH ('dark malate valve') is constitutively active and its lack leads to failure in early embryo development. Its activity is strictly regulated by post-translational redox-modification mediated via the ferredoxin-thioredoxin system and fine control via the NADP + /NADP(H) ratio, thereby maintaining redox homeostasis under changing conditions. The NADP-MDH as part of the 'light malate valve' plays an important role as a poising mechanism to adjust the ATP/NADPH ratio in the stroma. In addition, chloroplasts possess a NADP-dependent MDH isoform. Activities of NAD-dependent MDHs have been detected in mitochondria, peroxisomes, cytosol and plastids. Arabidopsis thaliana possesses nine genes encoding MDH isoenzymes. Depending on the co-enzyme specificity of the MDH isoforms, either NADH or NADPH can be transported indirectly. As components of malate valves, isoforms of malate dehydrogenases (MDHs) and dicarboxylate translocators catalyse the reversible interconversion of malate and oxaloacetate and their transport. Malate valves act as powerful systems for balancing the ATP/NAD(P)H ratio required in various subcellular compartments in plant cells.
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