Differential Expression, Tissue-Specific Distribution, and Posttranslational Controls of Phosphoenolpyruvate Carboxylase

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.

Validation of carbon isotopologue distribution measurements by GC-MS and application to13C-metabolic flux analysis of the tricarboxylic acid cycle inBrassica napusleaves

“…Since we have shown that PEPc contribution to Malate production was reduced in dark compared to light conditions, this result can only be explained by a higher transport of OAA/Malate from the cytosol to the mitochondria in dark conditions ( Figure 8 ). This idea is supported by the fact that PEPc is majorly localized to the cytosol (Caburatan and Park, 2021) and the recent identification of a mitochondrial malate importer in Arabidopsis with a decisive impact on mitochondrial respiration (Lee et al, 2021). Whether a higher malate import into mitochondria allows to increase the absolute metabolic flux of the TCA cycle in dark conditions in our experimental set-up remains to be elucidated.…”

“…Such shift could be attributed to both increased PEPc activity and TCA cycle inhibition in the light compared to dark conditions. Interestingly, PEPc activity is positively regulated by its light-dependent thioredoxin-mediated phosphorylation in C 3 and C 4 plants (Caburatan and Park, 2021). In the light, the lower respiration rate measured compared to dark conditions has been partly attributed to an inhibition of PDH and TCA cycle-derived decarboxylations (Tcherkez et al, 2005;Xu et al, 2021).…”

“…The non-cyclic nature of the TCA cycle has been previously proposed in illuminated leaves from works that used different experimental setup/labeling strategies. This non-cyclic nature in the light was mostly explained by the need to sustain de novo nitrogen assimilation and was supported by higher PEPc activities compared to dark conditions (Gauthier et al, 2010;Caburatan and Park, 2021). A first experiment was based on detached leaves of Xanthium stumarium and 13 C labeling with either 13 C1pyruvate or U-13 C-Pyruvate (Tcherkez et al, 2009).…”

Validation of carbon isotopologue distribution measurements by GC-MS and application to 13C-metabolic flux analysis of the tricarboxylic acid cycle in Brassica napus leaves

“…PEPc activity is positively regulated by its light-dependent thioredoxin-mediated phosphorylation in C 3 and C 4 plants ( Caburatan and Park, 2021 ). Consequently, PEPc is expected to be more active in the light than in the dark, as recently suggested in guard cell cultures based on the differential 13 C enrichment found for the C1 of glutamate ( Lima et al., 2021 ).…”

The Original Form of C4-Photosynthetic Phosphoenolpyruvate Carboxylase Is Retained in Pooids but Lost in Rice

“…Most non-photosynthetic PEPCs are cytosolic isoforms, but a chloroplast-targeted isoform was found in grass species rice ( Masumoto et al, 2010 ). Cytosolic PEPCs are predominant in plant species with multiple isoforms, from which gene expression patterns differ ( Caburatan and Park, 2021 ). In rice, four cytosolic PEPCs, one chloroplast PEPC, and one bacterial-type PEPC are known, but biological roles of these PEPCs seem to be not identical ( Masumoto et al, 2010 ; Yamamoto et al, 2014a , 2015 ).…”