Metabolite and post-translational control of phosphoenolpyruvate carboxylase from leaves and mesophyll cell protoplasts of Arabidopsis thaliana

Abstract

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 [ 32P]-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.