Abstract
Phosphoenolpyruvate carboxylase (PEPC) is a ubiquitous cytosolic enzyme, which is crucial for plant carbon metabolism. PEPC participates in photosynthesis by catalyzing the initial fixation of atmospheric CO2 and is abundant in both C4 and crassulacean acid metabolism leaves. PEPC is differentially expressed at different stages of plant development, mostly in leaves, but also in developing seeds. PEPC is known to show tissue-specific distribution in leaves and in other plant organs, such as roots, stems, and flowers. Plant PEPC undergoes reversible phosphorylation and monoubiquitination, which are posttranslational modifications playing important roles in regulatory processes and in protein localization. Phosphorylation activates the PEPC enzyme, making it more sensitive to glucose-6-phosphate and less sensitive to malate or aspartate. PEPC phosphorylation is known to be diurnally regulated and delicately changed in response to various environmental stimuli, in addition to light. PEPCs belong to a small gene family encoding several plant-type and distantly related bacterial-type PEPCs. This paper provides a minireview of the general information on PEPCs in both C4 and C3 plants.
Highlights
Phosphoenolpyruvate (PEP) carboxylase (PEPC) is a cytosolic enzyme involved in the irreversible β-carboxylation of PEP in the presence of HCO3− to yield oxaloacetate and inorganic phosphate (Pi) [1]
We focus on characteristics and posttranslational controls of C4-plant PEPCs, with information on higher-plant PEPCs provided for comparison
In the castor oil plant, monoubiquitination is more widespread than phosphorylation and appears to be a more predominant Posttranslational Modifications (PTMs) of the Class-1 PEPC [7,34]
Summary
Phosphoenolpyruvate (PEP) carboxylase (PEPC) is a cytosolic enzyme involved in the irreversible β-carboxylation of PEP in the presence of HCO3− to yield oxaloacetate and inorganic phosphate (Pi) [1]. PEPCs play crucial roles in a number of metabolic functions related to plant growth and development [2], such as carbon metabolism [3] and maintenance of cellular pH balance in opening stomata. These enzymes contribute to the accumulation of organic acids in fruits, in the supply of organic acids that are exuded from roots, and in Pi leaching to soil for aluminum detoxification [4,5]. PTPCs generally have a conserved N-terminal serine phosphorylation domain and can be either photosynthetic, such as in C4 and crassulacean acid metabolism (CAM) plants, or non-photosynthetic, such as in C3 plants [1,8]. We focus on characteristics and posttranslational controls of C4-plant PEPCs, with information on higher-plant PEPCs provided for comparison
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