R UBISCO : Structure, Regulatory Interactions, and Possibilities for a Better Enzyme

Department of Biochemistry, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, Nebraska 68588-0664, USA.
Annual review of plant biology (Impact Factor: 23.3). 02/2002; 53(1):449-75. DOI: 10.1146/annurev.arplant.53.100301.135233
Source: PubMed


Ribulose-1,5-bisphosphate (RuBP) carboxylase/oxygenase (Rubisco) catalyzes the first step in net photosynthetic CO2 assimilation and photorespiratory carbon oxidation. The enzyme is notoriously inefficient as a catalyst for the carboxylation of RuBP and is subject to competitive inhibition by O2, inactivation by loss of carbamylation, and dead-end inhibition by RuBP. These inadequacies make Rubisco rate limiting for photosynthesis and an obvious target for increasing agricultural productivity. Resolution of X-ray crystal structures and detailed analysis of divergent, mutant, and hybrid enzymes have increased our insight into the structure/function relationships of Rubisco. The interactions and associations relatively far from the Rubisco active site, including regulatory interactions with Rubisco activase, may present new approaches and strategies for understanding and ultimately improving this complex enzyme.

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    • "How biofilms and mats can establish this oversaturation, and why no development of gas bubbles was observed in the biofilm used in this study needs to be investigated further. Such high oxygen levels should inhibit net photosynthetic productivity, as they favor photorespiration (Spreitzer and Salvucci, 2002). This detrimental effect could be counteracted by carbon concentrating mechanisms (CCM), which elevate the CO 2 /O 2 ratio around the RuBisCO (review by Raven et al., 2008). "
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    ABSTRACT: In the present study depth profiles of light, oxygen, pH and photosynthetic performance in an artificial biofilm of the green alga Halochlorella rubescens in a porous substrate photobioreactor were recorded with microsensors. Biofilms were exposed to different light intensities (50–1,000 µmol photons m−2 s−1) and CO2 levels (0.04–5% v/v in air). The distribution of photosynthetically active radiation showed almost identical trends for different surface irradiances, namely: a relatively fast drop to a depth of about 250 µm, (to 5% of the incident), followed by a slower decrease. Light penetrated into the biofilm deeper than the Lambert-Beer Law predicted, which may be attributed to forward scattering of light, thus improving the overall light availability. Oxygen concentration profiles showed maxima at a depth between 50 and 150 µm, depending on the incident light intensity. A very fast gas exchange was observed at the biofilm surface. The highest oxygen concentration of 3.2 mM was measured with 1,000 µmol photons m−2 s−1 and 5% supplementary CO2. Photosynthetic productivity increased with light intensity and/or CO2 concentration and was always highest at the biofilm surface; the stimulating effect of elevated CO2 concentration in the gas phase on photosynthesis was enhanced by higher light intensities. The dissolved inorganic carbon concentration profiles suggest that the availability of the dissolved free CO2 has the strongest impact on photosynthetic productivity. The results suggest that dark respiration could explain previously observed decrease in growth rate over cultivation time in this type of PSBR. Our results represent a basis for understanding the complex dynamics of environmental variables and metabolic processes in artificial phototrophic biofilms exposed to a gas phase and can be used to improve the design and operational parameters of PSBRs.
    Biotechnology and Bioengineering 10/2015; DOI:10.1002/bit.25867 · 4.13 Impact Factor
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    • "On the other hand, a drop in Rubisco activity was observed in waterlogged barley plants as a result of restricted synthesis of both Rubisco subunits (Yordanova and Popova, 2001; Yordanova et al., 2004). The catalytic competence of Rubisco is attained following its activation by Rubisco activase in an ATP-dependent reaction (Spreitzer and Salvucci, 2002; Portis 2003). Two isoforms of Rubisco activase were evidenced in Festuca pratensis as a result of alternative splicing of a single gene (Jurczyk et al., 2015b). "
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    ABSTRACT: Increased precipitation expected during autumn and winter at higher latitudes in the northern hemisphere may lead to low temperature short-term waterlogging. The temperature of waterlogging was shown to be an important factor controlling plant reaction to this stress. Photosynthetic apparatus response to water excess in the soil at low temperature was examined in Festuca pratensis genotypes with contrasting freezing tolerance. The study was aimed to test the hypothesis whether changes in leaf water- soluble carbohydrate concentration brought about alterations in Rubisco activity may affect the photoacclimation to cold under water excess in the soil. The study investigated the effects of waterlogging during cold acclimation process on a set of chlorophyll a fluorescence parameters, water-soluble carbohydrates, expression of Rubisco activase gene, and Rubisco activity. It was shown that carbohydrate status affected by Rubisco activity might be crucial for the activation of non-photochemical mechanism of photoacclimation to cold under waterlogging. Altered Rubisco activity was only partially attributed to the expression of Rubisco activase gene. Additionally, low carbohydrate concentration in the leaves of waterlogged plants was the condition preventing sugar repression of photosynthesis, including RcaA expression. This indicates that sugar de-repression of photosynthetic genes may be considered a component of photosynthetic acclimation to cold under waterlogging.
    Environmental and Experimental Botany 09/2015; 122:60-67. DOI:10.1016/j.envexpbot.2015.09.003 · 3.36 Impact Factor
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    • "(Rubisco), which catalyzes the initial reaction of photosynthetic carbon assimilation , Rubisco activase plays an important role in the regulation of plant growth. So, Rubisco activase (RCA) adjusts the conformation of the active center of Rubisco removing tightly bound inhibitors thus contributing to the enzyme rapid carboxylation (Portis, 2003; Spreitzer and Salvucci, 2002; Carmo-Silva and Salvucci, 2013). Phosphoenolpyruvate carboxylase (PEPC) catalyzing irreversible carboxylation of phosphoenolpyruvate and converting it to oxaloacetate plays an important role in carbon and nitrogen metabolism of C3 plants. "
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    ABSTRACT: In early seedlings of wheat genotypes two isoforms of Rubisco activase with molecular weights of 42 and 46 kDa are expressed. Amounts of both isoforms significantly increase in early seedlings of the durum wheat genotype Barakatli-95 exposed to salt stress. But at the beginning of the tillering stage, the changes in quantities of both RCA isoforms are different in durum and bread wheat genotypes subjected to a 3-day drought stress. In leaves of the early seedlings of the studied wheat genotypes exposed to drought stress quantities of PEPC subunits increase compared to the control but they remain relatively stable in early roots and germinating seeds. However, quantities of its subunits decrease sharply in roots and germinating seeds of early seedlings under the influence of 100 mM NaCl. In flag leaves and ear elements of the Barakatli-95 genotype grown under normal water supply conditions protein quantities of PEPC subunits change differently depending on time. Changes in protein quantities of RCA, PEPC and Rubisco enzymes have been studied comparatively in ear elements and flag leaves after the fourth day of anthesis.
    Saudi Journal of Biological Sciences 09/2015; DOI:10.1016/j.sjbs.2015.09.013 · 1.26 Impact Factor
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