Photosynthesis: The Calvin Cycle

Heineke, Dieter; Scheibe, Renate

doi:10.1002/9780470015902.a0001291.pub2

Cited by 5 publications

(4 citation statements)

References 6 publications

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“…These redox cycles represent the basis for the fine control of enzyme activities. Activation and inactivation rates of the target enzymes are influenced by specific effectors, mainly substrates and products of the respective target enzyme, acting as a positive or negative effector (Heineke & Scheibe ). For instance, the activation of NADP‐MDH is only enabled when NADPH increases because it is not consumed in the CBC, e.g .…”

Section: Introductionmentioning

confidence: 99%

Malate valves: old shuttles with new perspectives

2018

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Malate valves act as powerful systems for balancing the ATP/NAD(P)H ratio required in various subcellular compartments in plant cells. As components of malate valves, isoforms of malate dehydrogenases (MDHs) and dicarboxylate translocators catalyse the reversible interconversion of malate and oxaloacetate and their transport. Depending on the co-enzyme specificity of the MDH isoforms, either NADH or NADPH can be transported indirectly. Arabidopsis thaliana possesses nine genes encoding MDH isoenzymes. Activities of NAD-dependent MDHs have been detected in mitochondria, peroxisomes, cytosol and plastids. In addition, chloroplasts possess a NADP-dependent MDH isoform. 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. 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. In contrast, the plastid NAD-MDH ('dark malate valve') is constitutively active and its lack leads to failure in early embryo development. 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. 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. 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.

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Section: Introductionmentioning

confidence: 99%

Malate valves: old shuttles with new perspectives

2018

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“…Oxidation leads to the inactivation of Calvin–Benson cycle enzymes and activation of G6PDH of the plastidial OPP pathway thus avoiding futile cycling. The coordination of metabolism during daily light and dark phases is controlled by this way in all green tissues ( 16 , 41 , 72 , 121 ).…”

Section: Thiol Switches Regulate Enzyme Activities Localizations and Moonlighting Functionsmentioning

confidence: 99%

Central Metabolism in Mammals and Plants as a Hub for Controlling Cell Fate

Selinski

Scheibe

2021

Antioxidants & Redox Signaling

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Significance: The importance of oxidoreductases in energy metabolism together with the occurrence of enzymes of central metabolism in the nucleus gave rise to the active research field aiming to understand moonlighting enzymes that undergo post-translational modifications (PTMs) before carrying out new tasks. Recent Advances: Cytosolic enzymes were shown to induce gene transcription after PTM and concomitant translocation to the nucleus. Changed properties of the oxidized forms of cytosolic glyceraldehyde 3-phosphate dehydrogenase, and also malate dehydrogenases and others, are the basis for a hypothesis suggesting moonlighting functions that directly link energy metabolism to adaptive responses required for maintenance of redox-homeostasis in all eukaryotes. Critical Issues: Small molecules, such as metabolic intermediates, coenzymes, or reduced glutathione, were shown to fine-tune the redox switches, interlinking redox state, metabolism, and induction of new functions via nuclear gene expression. The cytosol with its metabolic enzymes connecting energy fluxes between the various cell compartments can be seen as a hub for redox signaling, integrating the different signals for graded and directed responses in stressful situations. Future Directions: Enzymes of central metabolism were shown to interact with p53 or the assumed plant homologue suppressor of gamma response 1 (SOG1), an NAM, ATAF, and CUC transcription factor involved in the stress response upon ultraviolet exposure. Metabolic enzymes serve as sensors for imbalances, their inhibition leading to changed energy metabolism, and the adoption of transcriptional coactivator activities. Depending on the intensity of the impact, rerouting of energy metabolism, proliferation, DNA repair, cell cycle arrest, immune responses, or cell death will be induced. Antioxid. Redox Signal. 34, 1025–1047.

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“…The Calvin cycle is the primary cyclic pathway of carbon fixation and in higher plants is located in the stroma. The light reactions provide reducing power represented by the reduced form of nicotinamide adenine dinucleotide phosphate NADPH+H + and energy as ATP (Heineke & Scheibe 2007).…”

Section: Effect Of Uv-b In Calvin Cycle Enzymesmentioning

confidence: 99%

“…The Calvin cycle can be subdivided into three phases: (i) the carboxylation of ribulose 1,5-bisphosphate (RuBP), leading to the formation of two molecules of 3-phosphoglycerate (3PGA), (ii) the reduction of 3PGA, and (iii) the regeneration RuBP. The products of these reactions are triose phosphates, which are exported into the cytosol by a specific transporter to be converted to sucrose (Heineke & Scheibe 2007).…”

Section: Effect Of Uv-b In Calvin Cycle Enzymesmentioning

confidence: 99%

Effects of Ultraviolet-B Radiation in Plant Physiology

Nassour

Ayash

2021

Agriculture (Pol'nohospodárstvo)

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Over the past few decades, anthropogenic activities contributed to the depletion of the ozone layer, which increased the levels of solar ultraviolet-B (UV-B) radiation reaching the Earth`s surface. Generally, UV-B is harmful to all living organisms. It damages the cell`s Deoxyribonucleic acid (DNA), proteins, and lipids, and as a consequence, it affects the bio-membranes negatively. In this review, we summarize the major effects of UV-B in the plant`s main molecules and physiological reactions, in addition to the possible defence mechanisms against UV-B including accumulating UV-B absorbing pigments to alleviate the harmful impact of UV-B.

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Photosynthesis: The Calvin Cycle

Cited by 5 publications

References 6 publications

Malate valves: old shuttles with new perspectives

Malate valves: old shuttles with new perspectives

Central Metabolism in Mammals and Plants as a Hub for Controlling Cell Fate

Effects of Ultraviolet-B Radiation in Plant Physiology

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