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Redox regulation of Arabidopsis 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase

Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907, USA.
Plant physiology (Impact Factor: 7.39). 09/2002; 129(4):1866-71. DOI: 10.1104/pp.002626
Source: PubMed

ABSTRACT The cDNA for 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase of Arabidopsis encodes a polypeptide with an amino-terminal signal sequence for plastid import. A cDNA fragment encoding the processed form of the enzyme was expressed in Escherichia coli. The resulting protein was purified to electrophoretic homogeneity. The enzyme requires Mn(2+) and reduced thioredoxin (TRX) for activity. Spinach (Spinacia oleracea) TRX f has an apparent dissociation constant for the enzyme of about 0.2 microM. The corresponding constant for TRX m is orders of magnitude higher. In the absence of TRX, dithiothreitol partially activates the enzyme. Upon alkylation of the enzyme with iodoacetamide, the dependence on a reducing agent is lost. These results indicate that the first enzyme in the shikimate pathway of Arabidopsis appears to be regulated by the ferredoxin/TRX redox control of the chloroplast.

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    • "Transcriptional regulation of the shikimate pathway and aromatic amino acid metabolism in plants has so far not been studied extensively . The expression of DAHPS encoding the fi rst enzyme of the shikimate pathway (Fig. 2) is induced by physical wounding and methyl-jasmonate (Devoto et al., 2005; Yan et al., 2007), infi ltration with pathogenic Pseudomonas syringae strains (Keith et al., 1991), redox state (Entus et al., 2002) and abscisic acid (Leonhardt et al., 2004; Catala et al., 2007). The expression of the gene encoding EPSPS is induced in response to infection by the necrotrophic fungal pathogen Botrytis cinerea (Ferrari et al., 2007) and by sulfate starvation (Nikiforova et al., 2003). "
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    • "Thus, exogenous amino acids may restore the growth of ntrc plants by altering the homeostasis among biochemical pathways in chloroplasts. Attempts to identify thiol-redox-regulated enzymes have revealed putative targets for the thioredoxin systems both in the shikimate pathway and in the biosynthesis of aromatic amino acids, including 3-deoxy-D- arabino-heptulosonate 7-phosphate synthase and Trp synthase b (Entus et al., 2002; Balmer et al., 2006; Kolbe et al., 2006). Currently, we are exploring whether these enzymes are subjects for thiol-redox regulation by NTRC. "
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