Rubisco: its role in photorespiration

Keys, A. J.

doi:10.1098/rstb.1986.0040

Cited by 62 publications

(30 citation statements)

References 74 publications

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“…1). In most temperate C a plants at ambient levels of CO2 (0.03%), one molecule of RuBP is oxygenated for every 2.1-2.6 molecules carboxylated (Keys 1986). Phosphoglycollate is subsequently metabolized by a sequence of reactions in the chloroplasts, peroxisomes and mitochondria, which permits the recovery of some of the carbon by the photosynthetic reduction cycle.…”

Section: Introductionmentioning

confidence: 99%

The value of mutants unable to carry out photorespiration

et al. 1988

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Manipulation of the CO2 concentration of the atmosphere allows the selection of photorespiratory mutants from populations of seeds treated with powerful mutagens such as sodium azide. So far, barley lines deficient in activity of phosphoglycolate phosphatase, catalase, the glycine to serine conversion, glutamine synthetase, glutamate synthase, 2-oxoglutarate uptake and serine: glyoxylate aminotransferase have been isolated. In addition one line of pea lacking glutamate synthase activity and one barley line containing reduced levels of Rubisco are available. The characteristics of these mutations are described and compared with similar mutants isolated from populations of Arabidopsis. As yet, no mutant lacking glutamine synthetase activity has been isolated from Arabidopsis and possible reasons for this difference between barley and Arabidopsis are discussed. The value of these mutant plants in the elucidation of the mechanism of photorespiration and its relationships with CO2 fixation and amino acid metabolism are highlighted.

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Section: Introductionmentioning

confidence: 99%

The value of mutants unable to carry out photorespiration

et al. 1988

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“…The central importance in photorespiration of the NADH-dependent peroxisomal enzyme HPR has been accepted for almost 20 years (10,11,29) and is an enzyme thought to be especially active in green leaves (25,29). Recently, a novel HPR activity has been isolated and purified from spinach that can utilize NADPH in preference to NADH as a cofactor (12).…”

mentioning

confidence: 99%

“…Photorespiration is the apparently wasteful production of CO2 in the light by C3 plants and appears to be an unavoidable consequence of the 02 sensitivity of ribulose bisphosphate carboxylase (10,17 …”

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confidence: 99%

Metabolism of Hydroxypyruvate in a Mutant of Barley Lacking NADH-Dependent Hydroxypyruvate Reductase, an Important Photorespiratory Enzyme Activity

Murray¹,

Blackwell²,

Lea³

1989

Plant Physiol.

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A mutant of barley (Hordeum vulgare L.), LaPr 88/29, deficient in NADH-dependent hydroxypyruvate reductase (HPR) activity has been isolated. The activities of both NADH (5%) and NADPHdependent (19%) HPR were severely reduced in this mutant compared to the wild type. Although lacking an enzyme in the main carbon pathway of photorespiration, this mutant was capable of CO2 fixation rates equivalent to 75% of that of the wild type, in normal atmospheres and 50% 02. There and subsequently reduced to glycerate under the auspices of HPR.At atmospheric concentrations of CO2 greater than 0.2%, carbon is directed mainly through the carboxylase activity of ribulose bisphosphate carboxylase/oxygenase. This property was utilized by Somerville and Ogren (22) to identify and maintain conditional lethal mutants, with deficiencies in the photorespiratory pathway and consequently incapable of growth at ambient levels of CO2 (0.034%).Definitive studies of HPR activity in plants are hampered by the apparent multiplicity of enzymes showing this activity (12, 13). The central importance in photorespiration of the NADH-dependent peroxisomal enzyme HPR has been accepted for almost 20 years (10,11,29) and is an enzyme thought to be especially active in green leaves (25,29). Recently, a novel HPR activity has been isolated and purified from spinach that can utilize NADPH in preference to NADH as a cofactor (12). This form of HPR has been shown to be localized in the cytosol (14). The existence of glyoxylate reductase activity is also partially confusing.Although mutants deficient in some of the many steps of photorespiration have been isolated from populations of mutated seed of Arabidopsis thaliana (22) MATERIALS AND METHODS Plant MaterialThe M2 seeds of Hordeum vulgare L. (cv Klaxon) used for mutant screening were produced as described previously (20) in a glasshouse supplemented to a CO2 concentration of 0.7% (v/v). Selection of air-sensitive plants was carried out in a glasshouse with atmospheric CO2 concentrations, maintained at 200C. Preparation of Crude Enzyme ExtractThe preparation of crude enzyme extracts for use in measurements of enzyme activity and with PAGE was Plant Physiol. Vol. 91,1989 Assay of Hydroxypyruvate and Glyoxylate Reductase ActivityThe assays for NADH and NADPH-HPR activities were based on those described by Stabenau (24) and Kleczkowski and Randall (12). The final concentrations in 1 mL of assay mixture were 5 mm hydroxypyruvate, 25 mm phosphate buffer (pH 6.3), 0.2 mm NADH (NADPH) and 50 ,L crude enzyme extract. Reactions were initiated by the addition of hydroxypyruvate and the oxidation of NADH (NADPH) was monitored at 340 nm.GR activity was determined using the same assay system by the substitution of 5 mm glyoxylate for hydroxypyruvate in the reaction mixture. PAGENative PAGE and staining for NADH-HPR activity were carried out using 4.5% acrylamide slab gels (15, 27), other related reductases not being reversible are not detected by this method (12). Samples were loaded onto gels after mix...

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“…Oxygen concentrations can reach 300% air saturation levels in the water in which algae grow, even in their natural environment. At low CO 2 or high O 2 levels, oxygen out-competes CO 2 for RuBisCO (ribulose-1,5-bisphosphate carboxylase oxygenase, the enzyme that catalyzes the reduction of CO 2 ) catalysis thereby inhibiting carbon fixation (Keys, 1986). At such high concentrations algae can also experience oxygen toxicity (Shelp and Canvin, 1980;Fridovich, 1998).…”

Section: Growth Limitation In Sealed Fluidics Cardsmentioning

confidence: 99%

Biological system development for GraviSat: A new platform for studying photosynthesis and microalgae in space

Fleming

Bebout

Tan

et al. 2014

Life Sciences in Space Research

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Bebout, Vrad M.; Tan, Ming X.; Selch, Florian; and Ricco, Antonio J., "Biological system development for GraviSat: A new platform for studying photosynthesis and microalgae in space" (2014 Microalgae have great potential to be used as part of a regenerative life support system and to facilitate in-situ resource utilization (ISRU) on long-duration human space missions. Little is currently known, however, about microalgal responses to the space environment over long (months) or even short (hours to days) time scales. We describe here the development of biological support subsystems for a prototype "3U" (i.e., three conjoined 10-cm cubes) nanosatellite, called GraviSat, designed to experimentally elucidate the effects of space microgravity and the radiation environment on microalgae and other microorganisms. The GraviSat project comprises the co-development of biological handlingand-support technologies with implementation of integrated measurement hardware for photosynthetic efficiency and physiological activity in support of long-duration (3-12 months) space missions. It supports sample replication in a fully autonomous system that will grow and analyze microalgal cultures in 120 μL wells around the circumference of a microfluidic polymer disc; the cultures will be launched while in stasis, then grown in orbit. The disc spins at different rotational velocities to generate a range of artificial gravity levels in space, from microgravity to multiples of Earth gravity. Development of the biological support technologies for GraviSat comprised the screening of more than twenty microalgal strains for various physical, metabolic and biochemical attributes that support prolonged growth in a microfluidic disc, as well as the capacity for reversible metabolic stasis. Hardware development included that necessary to facilitate accurate and precise measurements of physical parameters by optical methods (pulse amplitude modulated fluorometry) and electrochemical sensors (ion-sensitive microelectrodes). Nearly all microalgal strains were biocompatible with nanosatellite materials; however, microalgal growth was rapidly inhibited (∼1 week) within sealed microwells that did not include dissolved bicarbonate due to CO 2 starvation. Additionally, oxygen production by some microalgae resulted in bubble formation within the wells, which interfered with sensor measurements. Our research achieved prolonged growth periods (>10 months) without excess oxygen production using two microalgal strains, Chlorella vulgaris UTEX 29 and Dunaliella bardawil 30 861, by lowering light intensities (2-10 μmol photons m −2 s −1 ) and temperature (4-12 • C). Although the experiments described here were performed to develop the GraviSat platform, the results of this study should be useful for the incorporation of microalgae in other satellite payloads with low-volume microfluidic systems.

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Rubisco: its role in photorespiration

Cited by 62 publications

References 74 publications

The value of mutants unable to carry out photorespiration

The value of mutants unable to carry out photorespiration

Metabolism of Hydroxypyruvate in a Mutant of Barley Lacking NADH-Dependent Hydroxypyruvate Reductase, an Important Photorespiratory Enzyme Activity

Biological system development for GraviSat: A new platform for studying photosynthesis and microalgae in space

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