InterPro domain: IPR021135

Phosphoenolpyruvate carboxylase (PEPCase), an enzyme found in all multicellular plants, catalyses the formation of oxaloacetate from phosphoenolpyruvate (PEP) and a hydrocarbonate ion [ 1 ]. This reaction is harnessed by C4 plants to capture and concentrate carbon dioxide into the photosynthetic bundle sheath cells. It also plays a key role in the nitrogen fixation pathway in legume root nodules: here it functions in concert with glutamine, glutamate and asparagine synthetases and aspartate amido transferase, to synthesise aspartate and asparagine, the major nitrogen transport compounds in various amine-transporting plant species [ 2 ].

PEPCase also plays an antipleurotic role in bacteria and plant cells, supplying oxaloacetate to the TCA cycle, which requires continuous input of C4 molecules in order to replenish the intermediates removed for amino acid biosynthesis [ 3 ]. The C terminus of the enzyme contains the active site that includes a conserved lysine residue, involved in substrate binding, and other conserved residues important for the catalytic mechanism [ 4 ].

Based on sequence similarity, PEPCase enzymes can be grouped into two distinct families, one found primarily in bacteria and plants, and another found primarily in archaea.

1. cDNA sequence and expression of a phosphoenolpyruvate carboxylase gene from soybean. Plant Mol. Biol. 20, 743-7
2. Alfalfa root nodule phosphoenolpyruvate carboxylase: characterization of the cDNA and expression in effective and plant-controlled ineffective nodules. Plant Mol. Biol. 20, 437-50
3. The phosphoenolpyruvate carboxylase gene of Corynebacterium glutamicum: molecular cloning, nucleotide sequence, and expression. Mol. Gen. Genet. 218, 330-9
4. Homologous genes for the C4 isoform of phosphoenolpyruvate carboxylase in a C3 and a C4 Flaveria species. Mol. Gen. Genet. 234, 275-84