Activation of the Potato Tuber ADP-glucose Pyrophosphorylase by Thioredoxin

Ballícora, Miguel A.; Frueauf, Jeremiah B.; Fu, Yingbin; Schürmann, Peter; Preiss, Jack

doi:10.1074/jbc.275.2.1315

Cited by 164 publications

(118 citation statements)

References 28 publications

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“…We were able to detect both subunits of ADP-glucose pyrophosphorylase, an enzyme known to be regulated by Trx in amyloplasts as well as chloroplasts, (18,48). Taking into consideration the previously unrecognized targets of starch metabolism listed in Table 2, it appears that Trx controls this process at several levels in plastids, including transport, breakdown, and synthesis.…”

Section: Identification Of Members Of the Ferredoxin͞trx System And Smentioning

confidence: 82%

“…First, enzymes shown to be regulated by Trx reside in the organelle, namely, ADP-glucose pyrophosphorylase (18), NADP-glucose 6-phosphate dehydrogenase (19,20), and ␣-glucan, water dikinase (21). Second, analyses of the constituent proteins (proteome) of amyloplasts have revealed the presence of a number of other enzymes that, in chloroplasts, are linked to Trx (refs.…”

Section: Resultsmentioning

confidence: 99%

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A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

Balmer

Vensel

Cai

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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160

137

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A growing number of processes throughout biology are regulated by redox via thiol-disulfide exchange. This mechanism is particularly widespread in plants, where almost 200 proteins have been linked to thioredoxin (Trx), a widely distributed small regulatory disulfide protein. The current study extends regulation by Trx to amyloplasts, organelles prevalent in heterotrophic plant tissues that, among other biosynthetic activities, catalyze the synthesis and storage of copious amounts of starch. Using proteomics and immunological methods, we identified the components of the ferredoxin͞Trx system (ferredoxin, ferredoxin-Trx reductase, and Trx), originally described for chloroplasts, in amyloplasts isolated from wheat starchy endosperm. Ferredoxin is reduced not by light, as in chloroplasts, but by metabolically generated NADPH via ferredoxin-NADP reductase. However, once reduced, ferredoxin appears to act as established for chloroplasts, i.e., via ferredoxinTrx reductase and a Trx (m-type). A proteomics approach in combination with affinity chromatography and a fluorescent thiol probe led to the identification of 42 potential Trx target proteins, 13 not previously recognized, including a major membrane transporter (Brittle-1 or ADP-glucose transporter). The proteins function in a range of processes in addition to starch metabolism: biosynthesis of lipids, amino acids, and nucleotides; protein folding; and several miscellaneous reactions. The results suggest a mechanism whereby light is initially recognized as a thiol signal in chloroplasts, then as a sugar during transit to the sink, where it is converted again to a thiol signal. In this way, amyloplast reactions in the grain can be coordinated with photosynthesis taking place in leaves.redox regulation ͉ target proteins ͉ ferredoxin-thioredoxin reductase O ur understanding of the function of the regulatory disulfide protein thioredoxin (Trx) has increased dramatically in the past few years, with the advent of new methodologies. Recent approaches make it possible to identify proteins linked to Trx by combining proteomics with affinity chromatography (1) or thiol probes (2-4). These capabilities have defined an extended role of Trx in chloroplasts (1, 5) and helped elucidate its function in other plant systems: mitochondria (6), seeds (2,3,7,8), and seedlings (4, 9). Currently almost 200 proteins appear to be linked to Trx in plants (10). One major organelle that has been neglected, however, is the amyloplast, a plastid of heterotrophic tissues that performs a wide range of biosynthetic reactions, including the synthesis and storage of abundant quantities of starch.To help fill this gap, we have applied proteomic and immunological approaches to investigate the occurrence and function of Trx in amyloplasts. We now report evidence that amyloplasts isolated from wheat starchy endosperm resemble chloroplasts in containing a complete ferredoxin͞Trx system composed of ferredoxin, ferredoxin-Trx reductase (FTR), and Trx (m-type). Application of affinity chromatography and fl...

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Section: Identification Of Members Of the Ferredoxin͞trx System And Smentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

Balmer

Vensel

Cai

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

160

137

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“…Moreover, the enzyme responsible for the first committed step in starch biosynthesis, ADP-glucose pyrophosphorylase (EC 2.7.7.27), has recently been shown to be redox-regulated (37)(38)(39). When searching the databases, we found the regulatory site sequence of potato GWD conserved in other GWD homologs (Fig.…”

Section: Discussionmentioning

confidence: 99%

α-Glucan, water dikinase (GWD): A plastidic enzyme with redox-regulated and coordinated catalytic activity and binding affinity

Mikkelsen

Mutenda

Mant

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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The recently discovered potato tuber (Solanum tuberosum) ␣-glucan, water dikinase (GWD) (formerly known as R1) catalyzes the phosphorylation of starch by a dikinase-type reaction mechanism in which the ␤-phosphate of ATP is transferred to either the C-6 or the C-3 position of the glucosyl residue of starch. In the present study, we found that the GWD enzyme is inactive in the oxidized form, which is accompanied by the formation of a specific intramolecular disulfide bond as determined by disulfide-linked peptide mapping. The regulatory properties of this disulfide linkage were confirmed by site-directed mutagenesis studies. Both reduced thioredoxin (Trx) f and Trx m from spinach leaves reduced and activated oxidized GWD at very low concentrations, with Trx f being the more efficient, yielding an S0.5 value of 0.4 M. Interestingly, GWD displays a reversible and selective binding to starch granules depending on the illumination state of the plant. Here we show that starch granule-bound GWD isolated from dark-adapted plants exists in the inactive, oxidized form, which is capable of reactivation upon treatment with reduced Trx. Furthermore, the soluble form of GWD was found in its fully reduced state, providing evidence of a Trx-controlled regulation mechanism linking enzymatic activity and specific binding affinities of a protein to an intracellular surface. The regulatory site sequence, CFATC, of potato GWD is conserved in chloroplast-targeted GWDs from other species, suggesting an overall redox regulation of the GWD enzyme.starch ͉ redox regulation ͉ thioredoxin

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“…On the contrary, ADP-Glc PPases from wheat, maize, and rice endosperm, as well as from potato tuber and cassava root, are regulated by 3-PGA and P i (3,(11)(12)(13)(14). In addition to the regulation by 3-PGA and P i , a redox control has also been proposed for potato tuber ADP-Glc PPase (15)(16)(17).…”

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confidence: 99%

The Different Large Subunit Isoforms of Arabidopsis thaliana ADP-glucose Pyrophosphorylase Confer Distinct Kinetic and Regulatory Properties to the Heterotetrameric Enzyme

Crevillén

Ballícora

Mérida

et al. 2003

Journal of Biological Chemistry

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153

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ADP-glucose pyrophosphorylase catalyzes the first and limiting step in starch biosynthesis and is allosterically regulated by the levels of 3-phosphoglycerate and phosphate in plants. ADP-glucose pyrophosphorylases from plants are heterotetramers composed of two types of subunits (small and large). In this study, the six Arabidopsis thaliana genes coding for ADP-glucose pyrophosphorylase isoforms (two small and four large subunits) have been cloned and expressed in an Escherichia coli mutant deficient in ADP-glucose pyrophosphorylase activity. The co-expression of the small subunit APS1 with the different Arabidopsis large subunits (APL1, APL2, APL3, and APL4) resulted in heterotetramers with different regulatory and kinetic properties. Heterotetramers composed of APS1 and APL1 showed the highest sensitivity to the allosteric effectors as well as the highest apparent affinity for the substrates (glucose-1-phosphate and ATP), whereas heterotetramers formed by APS1 and APL2 showed the lower response to allosteric effectors and the lower affinity for the substrates. No activity was detected for the second gene coding for a small subunit isoform (APS2) annotated in the Arabidopsis genome. This lack of activity is possibly due to the absence of essential amino acids involved in catalysis and/or in the binding of glucose-1-phosphate and 3-phosphoglycerate. Kinetic and regulatory properties of the different heterotetramers, together with sequence analysis has allowed us to make a distinction between sink and source enzymes, because the combination of different large subunits would provide a high plasticity to ADP-glucose pyrophosphorylase activity and regulation. This is the first experimental data concerning the role that all the ADP-glucose pyrophosphorylase isoforms play in a single plant species. This phenomenon could have an important role in vivo, because different large subunits would confer distinct regulatory properties to ADP-glucose pyrophosphorylase according to the necessities for starch synthesis in a given tissue.

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Activation of the Potato Tuber ADP-glucose Pyrophosphorylase by Thioredoxin

Cited by 164 publications

References 28 publications

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

A complete ferredoxin/thioredoxin system regulates fundamental processes in amyloplasts

α-Glucan, water dikinase (GWD): A plastidic enzyme with redox-regulated and coordinated catalytic activity and binding affinity

The Different Large Subunit Isoforms of Arabidopsis thaliana ADP-glucose Pyrophosphorylase Confer Distinct Kinetic and Regulatory Properties to the Heterotetrameric Enzyme

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