Biochemical and Biophysical Research Communications
Phosphoglycolate production catalyzed by ribulose diphosphate carboxylase
Abstract
An oxygen-dependent production of phosphoglycolate is catalyzed by purified soybean ribulose diphosphate carboxylase and by crude extracts of soybean and corn leaves. It is suggested that the phosphoglycolate produced in this reaction is the source of glycolate metabolized in photorespiration.
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Improving photosynthetic efficiency toward food security: Strategies, advances, and perspectives
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Response to Tcherkez and Farquhar: Rubisco adaptation is more limited by phylogenetic constraint than by catalytic trade-off
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Photorespiration – Rubisco's repair crew
2023, Journal of Plant PhysiologyThe photorespiratory repair pathway (photorespiration in short) was set up from ancient metabolic modules about three billion years ago in cyanobacteria, the later ancestors of chloroplasts. These prokaryotes developed the capacity for oxygenic photosynthesis, i.e. the use of water as a source of electrons and protons (with O2 as a by-product) for the sunlight-driven synthesis of ATP and NADPH for CO2 fixation in the Calvin cycle. However, the CO2-binding enzyme, ribulose 1,5-bisphosphate carboxylase (known under the acronym Rubisco), is not absolutely selective for CO2 and can also use O2 in a side reaction. It then produces 2-phosphoglycolate (2PG), the accumulation of which would inhibit and potentially stop the Calvin cycle and subsequently photosynthetic electron transport. Photorespiration removes the 2-PG and in this way prevents oxygenic photosynthesis from poisoning itself.
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This article is a review and update particularly on the enzyme components of plant photorespiration and their catalytic mechanisms, on the interaction of photorespiration with other metabolism and on its impact on the evolution of photosynthesis. This focus was chosen because a better knowledge of the enzymes involved and how they are embedded in overall plant metabolism can facilitate the targeted use of the now highly advanced methods of metabolic network modelling and flux analysis. Understanding photorespiration more than before as a process that enables, rather than reduces, plant photosynthesis, will help develop rational strategies for crop improvement.
Photorespiration is essential for acclimation to salt stress under high carbon availability in Chlamydomonas
2022, Algal ResearchCitation Excerpt :Photorespiration, a major pathway of plant primary metabolism, is mediated by the bifunctional enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO; [1]).
Photorespiration is crucial for acclimation to salt stress under high carbon availability, as demonstrated by the integrative analysis of CrHPR1 function in wild type and the mutant.
Photorespiration, a primary metabolic pathway in plants, results in the loss of photosynthetically fixed carbon. Therefore, it has become the prime target for crop improvement, particularly for the mitigation of serious challenges such as climate change and food shortage. Although the constitutive enzymes involved in photorespiration have been well identified, their detailed functions beyond metabolic processes remain unclear. This study aimed to determine whether photorespiration plays a potential role in the acclimatization of Chlamydomonas to salt stress under high carbon conditions, via enzymatic activity assessment, gene expression analysis, and detection of NADH and ROS contents in Chlamydomonas reinhardtii cells. Results demonstrated the crucial role of photorespiration in response to salt stress under high carbon availability, particularly involving the CrHPR1 site. Furthermore, we found that the tricarboxylic acid and glyoxylate cycles, which are responsible for NADH generation, are enhanced during acclimation to salt stress via photorespiration. These findings are of great significance for exploring the basic mechanisms of photorespiration and for the improvement of agronomic traits via genetic engineering. Furthermore, these results imply that both the involvement as well as preliminary function of photorespiration in stress response should be comprehensively considered in rational design.