Molecular Evolution of C4-Form Pepc in Maize: Comparison of Primary Sequences and Kinetic Properties with a Newly Cloned Recombinant Root-Form PEPC
Phosphoenolpyruvate carboxylases (PEPC, EC18.104.22.168) are encoded by a small mutigene family in plants. Each isoform PEPC is thought to play a specific physiological role. Three isoforms have been reported in C4 plants such as maize [1, 2], sorghum  and Flaveria trinervia ; the C4-form PEPC involved in C4 photosynthesis, the C3-form PEPC for housekeeping and the root-form PEPC prevalent in roots. Only for sorghum full-length cDNAs for the three isoforms were cloned and sequenced . Although we previously cloned and sequenced cDNAs for C4-form [5, 6] and C3-form PEPCs  in maize, the third one has remained unknown. We report here the cloning and prokaryotic expression of a full-length cDNA for the root-form PEPC and the comparison of its kinetic and regulatory properties with the C4-form PEPC . Structural features of C4-form PEPCs acquired during evolution of C4 photosynthesis are discussed.
Key wordsC metabolism enzymes isoforms cDNA cloning allosteric effectors phosphorylation/dephosphorylation
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