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the cDNA and expression in effective and plant-controlled ineffective
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MOL.GEN.GENET. 234(2) 275-284 (1992).
Phosphoenolpyruvate carboxylase (PEPCase), an enzyme found in all multi-
cellular plants, catalyses the formation of oxaloacetate from phospho-
enolpyruvate (PEP) and a hydrocarbonate ion . This reaction is harnessed
by C4 plants to capture and concentrate carbon dioxide into the photo-
synthetic 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 trans-
ferase, to synthesise aspartate and asparagine, the major nitrogen trans-
port compounds in various amine-transporting plant species . 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
The C-terminus of the enzyme contains the active site: this includes a
conserved lysine residue, involved in substrate binding, and other conserved
residues important for the catalytic mechanism .
PEPCARBXLASE is a 7-element fingerprint that provides a signature for
phosphoenolpyruvate carboxylases. The fingerprint was derived from an
initial alignment of 5 sequences: the motifs were drawn from conserved
regions spanning virtually the full alignment length - motifs 1 and 5
include regions encoded by PROSITE patterns PEPCASE_1 (PS00781) and
PEPCASE_2 (PS00393), which contain catalytically-important His and Lys
residues respectively, and motif 6 includes a region thought to be
involved in binding phosphoenolpyruvate. Two iterations on OWL 22.1 were
required to reach convergence, at which point a true set comprising 23
sequences was identified.
An update on SPTR37_9f identified a true set of 39 sequences.