The oxidative photosynthetic carbon cycle or C<sub>2</sub>cycle

Husic, Diane W.; Husic, H. David; Tolbert, N. E.; Black, Clanton C.

doi:10.1080/07352688709382234

Cited by 172 publications

(153 citation statements)

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“…The preferential localization of HPRs and GRs in the bundle sheath cells, where most of the glycolate metabolism occurs (13,33), seems consistent with the involvement of these activities in the oxidative photosynthetic carbon pathway, as has been proposed for the reductases from C3 species (11,13,(16)(17)(18)32). It is generally accepted that the enzyme compartmentation, metabolite transport and the sequence of reactions from P-glycolate up to the level of glycerate in the bundle sheath tissue are analogous to those found in C3 species (13,22,26,33 peroxisomes is most probably directly involved in the photorespiratory cycle, utilizing hydroxypyruvate derived from serine by the action of another peroxisomal enzyme, serine:glyoxylate aminotransferase (13).…”

Section: Reductases In Maizementioning

confidence: 51%

“…1), suggestive of negative cooperativity with respect to this reactant (29). The allosteric effect probably has no significance under physiological conditions in the peroxisomes, where the NADH-HPR reaction should prevail (13), but it may be useful in distinguishing the peroxisomal enzyme from the NADPH-preferring HPR. The latter, found in the 45 to 60% ppt.…”

Section: Differentiation Of Hydroxypyruvate and Glyoxylatementioning

confidence: 99%

“…With respect to C4 species, which show low (if any) rates of the photorespiratory CO2 evolution (13), there have been only few reports concern-both NADH-and NADPH-dependent HPRs and GRs from maize, a C4 plant, taking advantage of their differential solubility in salts, distinct substrate kinetics, and immunological properties. Characteristics of maize reductases are compared to those previously reported for purified HPR-1, HPR-2, and NADPH(NADH)-GR from spinach and other C3 species.…”

mentioning

confidence: 99%

“…Both enzymes have been proposed to serve as back-up reactions of the glycolate pathway, utilizing glyoxylate and hydroxypyruvate generated in the peroxisomes and 'leaked' or otherwise exported to the cytosol (1 1, [16][17][18][19][20]. The GR recycles glyoxylate back to the glycolate level, the latter is probably transported to the peroxisomes and converted to glycine, while glycerate formed by the cytosolic HPR may be directly exported to the chloroplasts to be metabolized to 3-phosphoglycerate by glycerate kinase (13). Thus, the two enzymes may have an auxillary role in the photorespiratory cycle, assuring that the P-glycolate-derived carbons of glyoxylate and hydroxypyruvate would eventually be returned to the chloroplasts for reduction through the reductive photosynthetic carbon pathway (Calvin-Benson cycle).…”

mentioning

confidence: 99%

“…Metabolism of glyoxylate and hydroxypyruvate in photosynthesizing cells is considered to be intimately related to the operation of the glycolate pathway (known also as the oxidative photosynthetic carbon cycle or C2-cycle), which is responsible for photorespiration in plants (13). In this process, which involves metabolism of several two-and three-carbon intermediates derived from P-glycolate in chloroplasts, glyoxylate Supported in part by the National Science Foundation grant is formed by oxidation of glycolate, while hydroxypyruvate is formed by transamination from serine.…”

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confidence: 99%

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Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Kleczkowski

Edwards²

1989

Plant Physiol.

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Metabolism of glyoxylate and hydroxypyruvate in photosynthesizing cells is considered to be intimately related to the operation of the glycolate pathway (known also as the oxidative photosynthetic carbon cycle or C2-cycle), which is responsible for photorespiration in plants (13). In this process, which involves metabolism of several two-and three-carbon intermediates derived from P-glycolate in chloroplasts, glyoxylate

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Section: Reductases In Maizementioning

confidence: 51%

Section: Differentiation Of Hydroxypyruvate and Glyoxylatementioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Kleczkowski

Edwards²

1989

Plant Physiol.

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Folic acid and folates: the feasibility for nutritional enhancement in plant foods

Scott¹,

Rébeillé²,

Fletcher³

2000

J. Sci. Food Agric.

289

237

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In mammalian and plant cells the folates play a key role in the methylation cycle and in the DNA biosynthesis cycle (in the de novo biosynthesis of purines and pyrimidines). Deficiency of folate in the diet is likely to result in a reduction in the capacity to synthesise DNA and maintain the usual rate of cell division. This most evidently results in the production of anaemia from folate deficiency due to a reduction in the biosynthesis of cells in the bone marrow. In addition it has been shown that high levels of plasma homocysteine occur which is an important risk factor in cardiovascular disease. Furthermore it has been shown that reduced maternal folate status is associated with the progressive increase in neural tube defects in infants. There is good evidence for folate deficiency in a considerable number of the population in developed countries, even where folate supplementation of foods is practised, and for a level of intake in excess of the recommended dietary allowance. This paper reviews the principal routes of folate biosynthesis in plants and the potential for increasing the levels of natural folates through conventional plant breeding and biotechnological means. The effect of the major food preservation processes on the levels of folates in plants is also reviewed. The current information about the bioavailability of folates from plant food sources, and how this might be improved, is also summarised. The important health benefits that would arise from increasing folate intake in the diet provide a strong incentive for considering how this might be achieved. © 2000 Society of Chemical Industry

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Photorespiration

Bauwe

2010

Encyclopedia of Life Sciences

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Photorespiration is the light‐dependent release of carbon dioxide initiated by ribulose‐1,5‐bisphosphate carboxylase/oxygenase ( Rubisco ) in oxygen‐producing photosynthetic organisms. It occurs because oxygen can substitute for carbon dioxide in the first reaction of the photosynthetic carbon dioxide‐fixation process, causing the idle synthesis of phosphoglycolate. Phosphoglycolate is scavenged in the photorespiratory C 2 cycle, which is an essential auxiliary metabolic pathway that allows photosynthesis in oxygen‐containing environments. Three out of four misdirected carbon atoms are recovered and the fourth is released as photorespiratory carbon dioxide. Absolute rates vary in different organisms and they also depend on environmental conditions, mainly oxygen, carbon dioxide and temperature. They are highest in C 3 plants and much reduced in other organisms, such as C 4 plants, algae and cyanobacteria. In the presence of oxygen, phosphoglycolate production is unavoidable and cannot be eliminated. Key concepts: Nearly all photosynthetic activity on earth is oxygen‐producing photosynthesis. Dictated by the biochemistry of carbon dioxide fixation, this unavoidably comes with the production of phosphoglycolate. When assessed by mass flow, excelled only by photosynthesis, phosphoglycolate production constitutes the second‐most important process in the land‐based biosphere. The scavenging of phosphoglycolate was a condition for the evolution of cyanobacteria, algae and plants. Oxygenic photosynthesis is only possible on the condition of adequate photorespiratory metabolism and life on earth would look very different without it. Oxygenic photosynthesis is coupled to photorespiratory carbon dioxide losses and this reduces competitiveness of C 3 plants in warm environments. Gene technology‐assisted breeding hopes to reduce these losses in crops.

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The oxidative photosynthetic carbon cycle or C₂cycle

Cited by 172 publications

References 338 publications

Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Folic acid and folates: the feasibility for nutritional enhancement in plant foods

Photorespiration

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The oxidative photosynthetic carbon cycle or C2cycle

Cited by 172 publications

References 338 publications

Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Identification of Hydroxypyruvate and Glyoxylate Reductases in Maize Leaves

Folic acid and folates: the feasibility for nutritional enhancement in plant foods

Photorespiration

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The oxidative photosynthetic carbon cycle or C₂cycle