The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
Hugh G. Nimmo - One of the best experts on this subject based on the ideXlab platform.
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Control of the phosphorylation of phosphoenolpyruvate carboxylase in higher plants
Archives of biochemistry and biophysics, 2003Co-Authors: Hugh G. NimmoAbstract:Phosphoenolpyruvate (PEP) carboxylase is regulated by reversible phosphorylation in higher plants. Recently several genes encoding PEP carboxylase kinase have been cloned. The purpose of this article is to assess the contribution that information on the structure and expression of these genes is making to our understanding of the posttranslational control of PEP carboxylase activity.
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Characterisation of a phosphoenolpyruvate carboxylase kinase gene from Sorghum
Science Access, 2001Co-Authors: James Hartwell, Gareth I. Jenkins, Hugh G. NimmoAbstract:Light-induced phosphorylation of phosphoenolpyruvate carboxylase plays an important role in C4 photosynthesis. It reduces the sensitivity of phosphoenolpyruvate carboxylase to malate and thereby allows this enzyme to fix bicarbonate even in the presence of a high concentration of malate in the mesophyll cell cytosol. Previous work has shown that light causes an increase in the activity of phosphoenolpyruvate carboxylase kinase in a process involving protein synthesis. Phosphoenolpyruvate carboxylase kinase genes have been cloned from a range of C3 and CAM species, but not so far from C4 species. We have identified a phosphoenolpyruvate carboxylase cDNA from the C4 plant Sorghum bicolor. It encodes a 307 residue protein of predicted Mr 32524, which, like other phosphoenolpyruvate carboxylase kinases, comprises a protein kinase catalytic domain with minimal extensions at the N- and C-terminal ends. However, relative to other phosphoenolpyruvate carboxylase kinases, the Sorghum enzyme contains an acidic 23-residue insert just after the catalytic loop. Structure prediction suggests that this insert would be exposed at the surface of the protein. Using in vitro transcription and translation, we have demonstrated that the protein encoded by this cDNA has high phosphoenolpyruvate carboxylase kinase activity. This appears to be the first report of a cloned phosphoenolpyruvate carboxylase kinase from a C4 plant. Data on the expression of the gene in response to light and to cycloheximide will be presented.
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The regulation of phosphoenolpyruvate carboxylase in CAM plants
Trends in Plant Science, 2000Co-Authors: Hugh G. NimmoAbstract:Phosphoenolpyruvate carboxylase catalyses the primary assimilation of CO2in Crassulacean acid metabolism plants. It is activated by phosphorylation, and this plays a major role in setting the day-night pattern of metabolism in these plants. The key factor that controls the phosphorylation state of phosphoenolpyruvate carboxylase is the activity of phosphoenolpyruvate carboxylase kinase. Recent work on Crassulacean acid metabolism plants has established this enzyme as a novel protein kinase and has provided new insights into the regulation of protein phosphorylation. Phosphoenolpyruvate carboxylase kinase is controlled by synthesis and degradation in response to a circadian oscillator. The circadian control of phosphoenolpyruvate carboxylase kinase can be overridden by changes in metabolite levels. The primary effect of the circadian oscillator in this system may be at the level of the tonoplast, and changes in kinase expression may be secondary to circadian changes in the concentration of a metabolite, perhaps cytosolic malate.
Bernard R. Glick - One of the best experts on this subject based on the ideXlab platform.
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The synthesis of phosphoenolpyruvate carboxylase in imbibing sorghum seeds
Biochemistry and cell biology = Biochimie et biologie cellulaire, 1991Co-Authors: Eli Khayat, Erwin B. Dumbroff, Bernard R. GlickAbstract:When sorghum seeds were imbibed either in the light or in the dark, the presence of newly synthesized phosphoenolpyruvate carboxylase (PEPC) could be detected immunologically after approximately 6 h. In addition, both PEPC mRNA and enzyme activity were detected in extracts of dry seeds prior to imbibition. By contrast, ribulose-1,5-bisphosphate carboxylase mRNA, protein, and activity, as well as chlorophyll, were not detected even after 24 h of imbibition. These observations suggest that the nonphotosynthetic form of PEPC is synthesized during seed development and may play an important role in the germinative process.Key words: phosphoenolpyruvate carboxylase, sorghum seeds, germination, ribulose-1,5-bisphosphate carboxylase.
Søren Laurentius Nielsen - One of the best experts on this subject based on the ideXlab platform.
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The carboxylase activity of Rubisco and the photosynthetic performance in aquatic plants.
Oecologia, 1991Co-Authors: Sven Beer, Kaj Sand-jensen, T. Vindbaek Madsen, Søren Laurentius NielsenAbstract:Activated carboxylase activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), as well as photosynthetic rates were measured for 42 species of freshwater and marine macrophytes. While the carboxylase activity varied greatly among the species investigated (0.2-12.5 μmol CO2 mg-1 chlorophyll min-1), the submersed freshwater plants showed significantly lower activities than emergent, floating leaved or secondary submersed forms. The variability in photosynthetic rates correlated with the carboxylase activity only for the marine macroalgae, and their photosynthesis to carboxylase activity ratios were close to 1. These plants also had a consistently high inorganic carbon transport capability, and it is suggested that ribulose-1,5-bisphosphate carboxylase/oxygenase activity is an important internal factor regulating the photosynthetic capacity within this plant group where, apparently, the internal CO2 concentration is high and photorespiration is suppressed. Among the freshwater forms, it appears that their much lower inorganic carbon transport ability, rather than their carboxylase activity, limits the photosynthetic process.
Robert Haselkorn - One of the best experts on this subject based on the ideXlab platform.
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Wheat acetyl-CoA carboxylase
Plant molecular biology, 1993Co-Authors: Piotr Gornicki, Robert HaselkornAbstract:The acetyl-CoA carboxylase present in both wheat germ and total wheat leaf protein contains ca. 220 kDa subunits. It is the major biotin-dependent carboxylase present in wheat chloroplasts. Active acetyl-CoA carboxylase purified from wheat germ is a homodimer with an apparent molecular mass of ca. 500 kDa. The enzyme from wheat germ or from wheat chloroplasts is sensitive to the herbicide haloxyfop at micromolar levels. The incorporation of 14C-acetate into fatty acids in freshly cut wheat seedling leaves provides a convenient in vivo assay for both acetyl-CoA carboxylase and haloxyfop.
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Genes for two subunits of acetyl coenzyme A carboxylase of Anabaena sp. strain PCC 7120: biotin carboxylase and biotin carboxyl carrier protein.
Journal of bacteriology, 1993Co-Authors: Piotr Gornicki, L A Scappino, Robert HaselkornAbstract:Genes for two subunits of acetyl-coenzyme A carboxylase, biotin carboxylase and biotin carboxyl carrier protein, have been cloned from Anabaena sp. strain PCC 7120. The two proteins are 181 and 447 amino acids long and show 40 and 57% identity to the corresponding Escherichia coli proteins, respectively. The sequence of the biotinylation site in Anabaena sp. strain PCC 7120 is MetLysLeu, not the MetLysMet found in other sequences of biotin-dependent carboxylases. The amino acid sequence of biotin carboxylase is also very similar (32 to 47% identity) to the sequence of the biotin carboxylase domain of other biotin-dependent carboxylases. Genes for these two subunits of acetyl-coenzyme A carboxylase are not linked in Anabaena sp. strain PCC 7120, contrary to the situation in E. coli, in which they are in one operon.
Eli Khayat - One of the best experts on this subject based on the ideXlab platform.
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The synthesis of phosphoenolpyruvate carboxylase in imbibing sorghum seeds
Biochemistry and cell biology = Biochimie et biologie cellulaire, 1991Co-Authors: Eli Khayat, Erwin B. Dumbroff, Bernard R. GlickAbstract:When sorghum seeds were imbibed either in the light or in the dark, the presence of newly synthesized phosphoenolpyruvate carboxylase (PEPC) could be detected immunologically after approximately 6 h. In addition, both PEPC mRNA and enzyme activity were detected in extracts of dry seeds prior to imbibition. By contrast, ribulose-1,5-bisphosphate carboxylase mRNA, protein, and activity, as well as chlorophyll, were not detected even after 24 h of imbibition. These observations suggest that the nonphotosynthetic form of PEPC is synthesized during seed development and may play an important role in the germinative process.Key words: phosphoenolpyruvate carboxylase, sorghum seeds, germination, ribulose-1,5-bisphosphate carboxylase.