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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    ABSTRACT: The aromatic amino acids phenylalanine, tyrosine and tryptophan in plants are not only essential components of protein synthesis, but also serve as precursors for a wide range of secondary metabolites that are important for plant growth as well as for human nutrition and health. The aromatic amino acids are synthesized via the shikimate pathway followed by the branched aromatic amino acid metabolic pathway, with chorismate serving as a major branch point intermediate metabolite. Yet, the regulation of their synthesis is still far from being understood. So far, only three enzymes in this pathway, namely, chorismate mutase of phenylalanine and tyrosine synthesis, tryptophan synthase of tryptophan biosynthesis and arogenate dehydratase of phenylalanine biosynthesis, proved experimentally to be allosterically regulated. The major biosynthesis route of phenylalanine in plants occurs via arogenate. Yet, recent studies suggest that an alternative route of phynylalanine biosynthesis via phenylpyruvate may also exist in plants, similarly to many microorganisms. Several transcription factors regulating the expression of genes encoding enzymes of both the shikimate pathway and aromatic amino acid metabolism have also been recently identified in Arabidopsis and other plant species.
    The Arabidopsis Book 01/2010; 8:e0132. DOI:10.1199/tab.0132
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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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    ABSTRACT: Chloroplast NADPH-thioredoxin reductase (NTRC) belongs to the thioredoxin systems that control crucial metabolic and regulatory pathways in plants. Here, by characterization of T-DNA insertion lines of NTRC gene, we uncover a novel connection between chloroplast thiol redox regulation and the control of photoperiodic growth in Arabidopsis (Arabidopsis thaliana). Transcript and metabolite profiling revealed severe developmental and metabolic defects in ntrc plants grown under a short 8-h light period. Besides reduced chlorophyll and anthocyanin contents, ntrc plants showed alterations in the levels of amino acids and auxin. Furthermore, a low carbon assimilation rate of ntrc leaves was associated with enhanced transpiration and photorespiration. All of these characteristics of ntrc were less severe when plants were grown under a long 16-h photoperiod. Transcript profiling revealed that the mutant phenotypes of ntrc were accompanied by differential expression of genes involved in stomatal development, chlorophyll biosynthesis, chloroplast biogenesis, and circadian clock-linked light perception systems in ntrc plants. We propose that NTRC regulates several key processes, including chlorophyll biosynthesis and the shikimate pathway, in chloroplasts. In the absence of NTRC, imbalanced metabolic activities presumably modulate the chloroplast retrograde signals, leading to altered expression of nuclear genes and, ultimately, to the formation of the pleiotrophic phenotypes in ntrc mutant plants.
    Plant physiology 02/2009; 149(3):1261-76. DOI:10.1104/pp.108.133777 · 7.39 Impact Factor
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    • "Another mechanism that may result in the reduction in phenylpropanoids in ref4 is alterations in posttranslational regulation of the enzymes of either pathway. In plants, both the provision of carbon via the Calvin cycle and the activity of two shikimate pathway enzymes (DAHP-synthase and shikimate kinase) are activated by reduced thioredoxin (Schmidt and Schultz 1987; Entus et al. 2002; Balmer et al. 2003). Thus the channeling of carbon into aromatic amino acid biosynthesis is tightly coupled to the redox potential of the cell. "
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    ABSTRACT: Plants synthesize an array of natural products that play diverse roles in growth, development, and defense. The plant-specific phenylpropanoid metabolic pathway produces as some of its major products flavonoids, monolignols, and hydroxycinnamic- acid conjugates. The reduced epidermal fluorescence 4 (ref4) mutant is partially dwarfed and accumulates reduced quantities of all phenylpropanoid-pathway end products. Further, plants heterozygous for ref4 exhibit intermediate growth and phenylpropanoid-related phenotypes, suggesting that these mutations are semidominant. The REF4 locus (At2g48110) was cloned by a combined map- and sequencing-based approach and was found to encode a large integral membrane protein that is unique to plants. The mutations in all ref4 alleles cause substitutions in conserved amino acids that are located adjacent to predicted transmembrane regions. Expression of the ref4-3 allele in wild-type and null REF4 plants caused reductions in sinapoylmalate content, lignin content, and growth, demonstrating that the mutant alleles are truly semidominant. Further, a suppressor mutant was isolated that abolishes a WW protein-protein interaction domain that may be important for REF4 function.
    Genetics 05/2008; 178(4):2237-51. DOI:10.1534/genetics.107.083881 · 4.87 Impact Factor
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