Differential Expression, Tissue-Specific Distribution, and Posttranslational Controls of Phosphoenolpyruvate Carboxylase (original) (raw)
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Biochemical Journal, 2011
PEPC [PEP (phosphoenolpyruvate) carboxylase] is a tightly controlled enzyme located at the core of plant C-metabolism that catalyses the irreversible β-carboxylation of PEP to form oxaloacetate and Pi. The critical role of PEPC in assimilating atmospheric CO2 during C4 and Crassulacean acid metabolism photosynthesis has been studied extensively. PEPC also fulfils a broad spectrum of non-photosynthetic functions, particularly the anaplerotic replenishment of tricarboxylic acid cycle intermediates consumed during biosynthesis and nitrogen assimilation. An impressive array of strategies has evolved to co-ordinate in vivo PEPC activity with cellular demands for C4–C6 carboxylic acids. To achieve its diverse roles and complex regulation, PEPC belongs to a small multigene family encoding several closely related PTPCs (plant-type PEPCs), along with a distantly related BTPC (bacterial-type PEPC). PTPC genes encode ~110-kDa polypeptides containing conserved serine-phosphorylation and lysine-...
Plant Science, 2005
The four phosphoenolpyruvate carboxylase encoding genes (1-4) of Arabidopsis thaliana were found to be expressed in rosette leaves, with PEPC2 mRNA being the major species. The enzyme activity was sensitive to feedback inhibition by malate, aspartate and glutamate and this effect was antagonized by glucose-6-phosphate and modulated after a dark-light transition. Taken together, the light/dark differences detected in pH response, malate sensitivity, phosphoenolpyruvate carboxylase kinase1 (PEPCk1) transcript content, and in vivo [ 32 P]phosphate labelling indicates that PEPC is subjected to reversible, light-dependent phosphorylation on its N-terminal regulatory serine. The light-transduction pathway in isolated mesophyll cell protoplasts involves a PI-dependent phospholipase C (PI-PLC), the second messenger inositol 1,4,5 trisphosphate (IP 3 ), calcium fluxes via IP 3 -dependent tonoplast calcium channels, photosynthetic electron transport and PEPCk1 synthesis. #
PLANT PHYSIOLOGY, 1991
Control of C4 photosynthesis and Crassulacean acid metabolism (CAM) is, in part, mediated by the diel regulation of phosphoenolpyruvate carboxylase (PEPC) activity. The nature of this regulation of PEPC in the leaf cell cytoplasm of C4 and CAM plants is both metabolite-related and posttranslational. Specifically, the regulatory properties of the enzyme vary in accord with the physiological activity of C4 photosynthesis and CAM: PEPC is less sensitive to feedback inhibition by L-malate under light (C4 plants) or at night (CAM plants) than in darkness (C4) or during the day (CAM). While the view that a light-induced change in the aggregation state of the holoenzyme is a general mechanism for the diel regulation of PEPC activity in CAM plants is currentiy in dispute, there is no supportive in vivo evidence for such a tetramer/dimer interconversion in C4 plants. In contrast, a wealth of in vitro and in vivo data has accumulated in support of the view that the reversible phosphorylation of a specific, N-terminal regulatory serine residue in PEPC (e.g. Ser-15 or Ser-8 in the maize or sorghum enzymes, respectively) plays a key, if not cardinal, role in the posttranslational regulation of the carboxylase by light/ dark or day/night transitions in both C4 and CAM plants, respectively. Phosphoenolpyruvate carboxylase (PEPC2, EC 4.1.1.31) catalyzes the irreversible ,B-carboxylation of PEP in the pres
Phospho\u3ci\u3eenol\u3c/i\u3epyruvate Carboxylase: A Ubiquitous, Highly Regulated Enzyme in Plants
1996
Since plant phosphoenolpyruvate carboxylase (PEPC) was last reviewed in the Annual Review of Plant Physiology over a decade ago (O’Leary 1982), significant advances have been made in our knowledge of this oligomeric, cytosolic enzyme. This review highlights this exciting progress in plant PEPC research by focusing on the three major areas of recent investigation: the enzymology of the protein; its posttranslational regulation by reversible protein phosphorylation and opposing metabolite effectors; and the structure, expression, and molecular evolution of the nuclear PEPC genes. It is hoped that the next ten years will be equally enlightening, especially with respect to the three-dimensional structure of the plant enzyme, the molecular analysis of its highly regulated protein-Ser/Thr kinase, and the elucidation of its associated signal-transduction pathways in various plant cell types
PHOSPHO ENOL PYRUVATE CARBOXYLASE: A Ubiquitous, Highly Regulated Enzyme in Plants
Annual Review of Plant Physiology and Plant Molecular Biology, 1996
Since plant phosphoenolpyruvate carboxylase (PEPC) was last reviewed in the Annual Review of Plant Physiology over a decade ago (O'Leary 1982), significant advances have been made in our knowledge of this oligomeric, cytosolic enzyme. This review highlights this exciting progress in plant PEPC research by focusing on the three major areas of recent investigation: the enzymology of the protein; its posttranslational regulation by reversible protein phosphorylation and opposing metabolite effectors; and the structure, expression, and molecular evolution of the nuclear PEPC genes. It is hoped that the next ten years will be equally enlightening, especially with respect to the three-dimensional structure of the plant enzyme, the molecular analysis of its highly regulated protein-Ser/ Thr kinase, and the elucidation of its associated signal-transduction pathways in various plant cell types.
Biochemical and Biophysical Research Communications, 2001
In Crassulacean acid metabolism (CAM) plants, phosphoenolpyruvate carboxylase (PEPC) is subject to day-night regulatory phosphorylation of a conserved serine residue in the plant enzyme's N-terminal domain. The dark increase in PEPC-kinase (PEPC-k) activity is under control of a circadian oscillator, via the enhanced expression of the corresponding gene (1). The signaling cascade leading to PEPC-k upregulation was investigated in leaves and mesophyll cell protoplasts of the facultative, salt-inducible CAM species, Mesembryanthemum crystallinum. Mesophyll cell protoplasts had the same PEPC-k activity as leaves from which they were prepared (i.e., high at night, low during the day). However, unlike C 4 protoplasts (2), CAM protoplasts did not show marked PEPC-k up-regulation when isolated during the day and treated with a weak base such as NH 4 Cl. Investigations using various pharmacological reagents established the operation, in the darkened CAM leaf, of a PEPC-k cascade including the following components: a phosphoinositide-dependent phospholipase C (PI-PLC), inositol 1,4,5 P (IP 3)-gated tonoplast calcium channels, and a putative Ca 2؉ /calmodulin protein kinase. These results suggest that a similar signaling machinery is involved in both C 4 (2, 3) and CAM plants to regulate PEPC-k activity, the phosphorylation state of PEPC, and, thus, carbon flux through this enzyme during CAM photosynthesis.