Diurnal changes in the properties of phosphoenolpyruvate carboxylase in <i>Bryophyllum</i> leaves: a possible co valent modification

Nimmo, Gillian A.; Nimmo, Hugh G.; Fewson, Charles A.; Wilkins, Malcolm B.

doi:10.1016/0014-5793(84)80600-6

Cited by 120 publications

(95 citation statements)

References 20 publications

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“…The activity of PEPc was assayed and its apparent K i for l-malate estimated as described by Nimmo et al (1984). PEPc kinase activity in desalted extracts was assayed according to the method of Carter et al (1991) using purified dephosphorylated PEPc from Kalanchoë fedtschenkoi as the substrate.…”

Section: Pepc and Pepc Kinase Assaysmentioning

confidence: 99%

“…The day/night regulation of flux through PEPc is achieved by reversible phosphorylation that reduces the sensitivity of the enzyme to inhibition by L-malate with the phosphorylated, malateinsensitive (active) form of PEPc present at night (Nimmo et al, 1984(Nimmo et al, , 1986. The phosphorylation state of PEPc is determined by the presence or absence of a specific Ca 2ϩ -independent protein kinase termed PEPc kinase (Carter et al, 1991;Li and Chollet, 1994).…”

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confidence: 99%

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Metabolite Control Overrides Circadian Regulation of Phosphoenolpyruvate Carboxylase Kinase and CO2 Fixation in Crassulacean Acid Metabolism

et al. 1999

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Phosphoenolpyruvate carboxylase (PEPc) catalyzes the primary fixation of CO 2 in Crassulacean acid metabolism plants. Flux through the enzyme is regulated by reversible phosphorylation. PEPc kinase is controlled by changes in the level of its translatable mRNA in response to a circadian rhythm. The physiological significance of changes in the levels of PEPc-kinase-translatable mRNA and the involvement of metabolites in control of the kinase was investigated by subjecting Kalanchoë daigremontiana leaves to anaerobic conditions at night to modulate the magnitude of malate accumulation, or to a rise in temperature at night to increase the efflux of malate from vacuole to cytosol. Changes in CO 2 fixation and PEPc kinase activity reflected those in kinase mRNA. The highest rates of CO 2 fixation and levels of kinase mRNA were observed in leaves subjected to anaerobic treatment for the first half of the night and then transferred to ambient air. In leaves subjected to anaerobic treatment overnight and transferred to ambient air at the start of the day, PEPc-kinase-translatable mRNA and activity, the phosphorylation state of PEPc, and fixation of atmospheric CO 2 were significantly higher than those for control leaves for the first 3 h of the light period. A nighttime temperature increase from 19°C to 27°C led to a rapid reduction in kinase mRNA and activity; however, this was not observed in leaves in which malate accumulation had been prevented by anaerobic treatment. These data are consistent with the hypothesis that a high concentration of malate reduces both kinase mRNA and the accumulation of the kinase itself.

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Section: Pepc and Pepc Kinase Assaysmentioning

confidence: 99%

mentioning

confidence: 99%

Metabolite Control Overrides Circadian Regulation of Phosphoenolpyruvate Carboxylase Kinase and CO2 Fixation in Crassulacean Acid Metabolism

et al. 1999

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“…The extraction and assay of PEPC was modified from the method described by Nimmo et al (1984). Leaves were homogenized in extraction buffer (200 mm Tris-HCl, pH 8.0, 2 mm EDTA, 1 mm DTT, 1 mm benzamidine, 10 mm malate, 2% [w/v] PEG 20,000, and 179 mm NaHCO 3 ).…”

Section: Apparent Activation State Of Pepcmentioning

confidence: 99%

Modulation of Rubisco Activity during the Diurnal Phases of the Crassulacean Acid Metabolism Plant Kalanchoëdaigremontiana

Maxwell¹,

Borland²,

Haslam³

et al. 1999

Plant Physiology

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The regulation of Rubisco activity was investigated under high, constant photosynthetic photon flux density during the diurnal phases of Crassulacean acid metabolism in Kalanchoëdaigremontiana Hamet et Perr. During phase I, a significant period of nocturnal, C4-mediated CO2 fixation was observed, with the generated malic acid being decarboxylated the following day (phase III). Two periods of daytime atmospheric CO2 fixation occurred at the beginning (phase II, C4–C3 carboxylation) and end (phase IV, C3–C4 carboxylation) of the day. During the 1st h of the photoperiod, when phosphoenolpyruvate carboxylase was still active, the highest rates of atmospheric CO2 uptake were observed, coincident with the lowest rates of electron transport and minimal Rubisco activity. Over the next 1 to 2 h of phase II, carbamylation increased rapidly during an initial period of decarboxylation. Maximal carbamylation (70%–80%) was reached 2 h into phase III and was maintained under conditions of elevated CO2 resulting from malic acid decarboxylation. Initial and total Rubisco activity increased throughout phase III, with maximal activity achieved 9 h into the photoperiod at the beginning of phase IV, as atmospheric CO2 uptake recommenced. We suggest that the increased enzyme activity supports assimilation under CO2-limited conditions at the start of phase IV. The data indicate that Rubisco activity is modulated in-line with intracellular CO2 supply during the daytime phases of Crassulacean acid metabolism.

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“…It must be recognized, however, that changes in the amount of enzyme brought about by changes in gene expression are not the only way to regulate an enzyme's activity. In Bryophyllum, changes in phosphoenolpyruvate activity appear to be due to post-translational modification (phosphorylation) of the enzyme (Nimmo et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

Circadian Changes in Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Distribution Inside Individual Chloroplasts Can Account for the Rhythm in Dinoflagellate Carbon Fixation

2001

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Previous studies of photosynthetic carbon fixation in the marine alga Gonyaulax have shown that the reaction rates in vivo vary threefold between day and night but that the in vitro activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), which catalyzes the rate-limiting step in this process, remains constant. Using protein gel blotting, we confirm that Rubisco protein levels are constant over time. We present simultaneous measurements of the rhythms of CO 2 fixation and O 2 evolution and show that the two rhythms are ‫ف‬ 6 hr out of phase. We further show that the distribution of Rubisco within chloroplasts varies as a function of circadian time and that this rhythm in Rubisco distribution correlates with the CO 2 fixation rhythm. At times of high carbon fixation, Rubisco is found in pyrenoids, regions of the chloroplasts located near the cell center, and is separated from most of the light-harvesting protein PCP (for peridininchlorophyll a -protein), which is found in cortical regions of the plastids. We propose that the rhythm in Rubisco distribution is causally related to the rhythm in carbon fixation and suggest that several mechanisms involving enzyme sequestration could account for the increase in the efficiency of carbon fixation. INTRODUCTIONCircadian rhythms are daily biochemical changes that are driven by circadian clocks but are not by themselves clocks. Biological clocks are characterized by transcriptional feedback loops that maintain their own oscillation (Dunlap, 1999;Shearman et al., 2000) and that receive phasing information from changes in light intensity (Crosthwaite et al., 1997;Ceriani et al., 1999) or temperature (Liu et al., 1998) that allows them to synchronize their oscillations with natural environmental cycles. In contrast, circadian rhythms are changes in an organism's physiology or biochemistry that, although rhythmic under constant conditions, are incapable of independent oscillations and instead require the timing signals provided by circadian clocks.A useful theoretical framework for understanding many biological rhythms is the notion that a central oscillator provides periodic regulatory signals that result in the control of a rate-limiting step (RLS) in a given biochemical pathway. Thus, understanding the regulation of the RLS is vital to understanding the clock's effect on organisms. For example, previous work on the bioluminescence rhythm in the dinoflagellate Gonyaulax has shown that both dinoflagellate luciferase (the reaction catalyst) and the luciferin (substrate) binding protein LBP contribute to the RLS of the nightly bioluminescence reaction. Cellular levels of both proteins vary seven-to 10-fold between day and night in phase with the 50-to 100-fold variations in bioluminescence capacity (Johnson et al., 1984;Morse et al., 1989a). In a vertebrate example, N -acetyltransferase catalyzes the RLS in vertebrate melatonin synthesis, and N -acetyltransferase levels correlate with the circulating melatonin rhythm (Gastel et al., 1998).Rhythms are generally con...

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Diurnal changes in the properties of phosphoenolpyruvate carboxylase in Bryophyllum leaves: a possible co valent modification

Cited by 120 publications

References 20 publications

Metabolite Control Overrides Circadian Regulation of Phosphoenolpyruvate Carboxylase Kinase and CO2 Fixation in Crassulacean Acid Metabolism

Metabolite Control Overrides Circadian Regulation of Phosphoenolpyruvate Carboxylase Kinase and CO2 Fixation in Crassulacean Acid Metabolism

Modulation of Rubisco Activity during the Diurnal Phases of the Crassulacean Acid Metabolism Plant Kalanchoëdaigremontiana

Circadian Changes in Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Distribution Inside Individual Chloroplasts Can Account for the Rhythm in Dinoflagellate Carbon Fixation

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