Identification of a Novel Enzyme Required for Starch Metabolism in Arabidopsis Leaves. The Phosphoglucan, Water Dikinase

Kötting, Oliver; Pusch, Kerstin; Tiessen, Axel; Geigenberger, Peter; Steup, Martin; Ritte, Gerhard

doi:10.1104/pp.104.055954

Cited by 245 publications

(279 citation statements)

References 36 publications

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“…In this study, the native starch granules had been isolated from leaves performing net starch degradation, and the starch-derived phosphoglucans reflect the in vivo phosphorylation of the granule surface. Finally, as observed with native starch granules, PWD acts mainly downstream of GWD (Figure 2; Kö tting et al, 2005). In summary, both the high rates of phosphorylation and the phosphorylation pattern, as observed in the current study, strongly suggest that crystalline maltodextrins (at least if they represent the B-type allomorph) mimic important features of the physiological carbohydrate substrate of GWD, i.e.…”

Section: Discussionmentioning

confidence: 53%

“…Finally, R1 was identified as a glucan, water dikinase (GWD) that selectively phosphorylates amylopectin-related glucosyl residues in the C6 position (Ritte et al, 2002(Ritte et al, , 2006. A second dikinase (designated PWD) has also been described that catalyzes the phosphorylation of glucosyl residues in the C3 position (Baunsgaard et al, 2005;Kö tting et al, 2005;Ritte et al, 2006). However, at a mechanistic level, it remained unclear how phosphorylation affects starch turnover.…”

Section: Discussionmentioning

confidence: 99%

“…Using native starch granules as the carbohydrate substrate, PWD activity was detectable only if the starch particles had been pre-phosphorylated by GWD (Kö tting et al, 2005). In this study, the 33 P labeling of MD cryst by recombinant PWD was studied using a similar approach to that described above ( Figure 2a).…”

Section: Pwd Phosphorylates Maltodextrins That Have Been Pre-phosphormentioning

confidence: 99%

“…maizegdb.org). For the expression and purification of recombinant GWD from Solanum tuberosum L., and PWD and BAM3 from Arabidopsis thaliana L. (At4g17090), see Ritte et al (2002), Kö tting et al (2005) and Edner et al (2007).…”

Section: Chemicals and Enzymesmentioning

confidence: 99%

“…glucan, water dikinase (GWD, EC 2.7.9.4; Ritte et al, 2002Ritte et al, , 2006 and phosphoglucan, water dikinase (PWD, EC 2.7.9.5; Kö tting et al, 2005) display significant activities with granular starch. GWD and PWD selectively catalyze phosphorylation of the C6 and C3 positions, respectively, of glucosyl residues within amylopectin molecules, and are both required for the normal metabolism of transitory starch and for development of the entire plant as well (Baunsgaard et al, 2005;Kö tting et al, 2005;Yu et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Glucan, water dikinase phosphorylates crystalline maltodextrins and thereby initiates solubilization

Hejazi¹,

Fettke

Haebel

et al. 2008

The Plant Journal

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SummaryStarch phosphorylation by glucan, water dikinase (GWD; EC 2.7.9.4) is an essential step in the breakdown of native starch particles, but the underlying mechanisms have remained obscure. In this paper, the initial reactions of starch degradation were analyzed using crystallized maltodextrins as model carbohydrates. As revealed by X-ray diffraction analysis, the crystallized maltodextrins represent the B-type starch allomorph. Recombinant GWD phosphorylated crystalline maltodextrins with a high specific activity (55-60 nmol mg )1 protein min )1 ), but exhibited very little activity with the same maltodextrins that had been solubilized by heat treatment. Recombinant phosphoglucan, water dikinase (PWD; EC 2.7.9.5) utilized the crystalline maltodextrins only when pre-phosphorylated by GWD. Phosphorylation of crystalline maltodextrins, as catalyzed by GWD, initiated solubilization of neutral as well as phosphorylated glucans. In both the insoluble and the soluble state, mono-, di-and triphosphorylated a-glucans were observed, with wide and overlapping ranges of degree of polymerization. Thus, the substrate specificity of the GWD is defined by the physical arrangement of a-glucans rather than by structural parameters, such as the distribution of branching points or degree of polymerization. Unlike GWD and PWD, recombinant b-amylase isozyme 3 (BAM3), which has been shown to be essential for plastidial starch degradation, preferentially degraded soluble maltodextrins rather than crystallized glucans. In summary, two conclusions were reached. Firstly, carbohydrate targets of GWD are primarily defined by the molecular order of glucan helices. Secondly, GWD-catalyzed phosphorylation mediates the phase transition of glucans from a highly ordered to a less ordered and hydrated state.

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Pwd Phosphorylates Maltodextrins That Have Been Pre-phosphormentioning

confidence: 99%

Section: Chemicals and Enzymesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Glucan, water dikinase phosphorylates crystalline maltodextrins and thereby initiates solubilization

Hejazi¹,

Fettke

Haebel

et al. 2008

The Plant Journal

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Plant α‐glucan phosphatases SEX4 and LSF2 display different affinity for amylopectin and amylose

et al. 2016

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These authors contributed equally to the work. The plant glucan phosphatases Starch EXcess 4 (SEX4) and Like Sex Four2 (LSF2) apply different starch binding mechanisms. SEX4 contains a carbohydrate binding module, and LSF2 has two surface binding sites (SBSs). We determined K Dapp for amylopectin and amylose, and K D for b-cyclodextrin and validated binding site mutants deploying affinity gel electrophoresis (AGE) and surface plasmon resonance. SEX4 has a higher affinity for amylopectin; LSF2 prefers amylose and b-cyclodextrin. SEX4 has 50-fold lower K Dapp for amylopectin compared to LSF2. Molecular dynamics simulations and AGE data both support long-distance mutual effects of binding at SBSs and the active site in LSF2.

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Starch Biosynthesis and Degradation in Plants

Lloyd¹,

Kötting²

2016

Encyclopedia of Life Sciences

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Starch is the main form in which plants store carbon. Its presence and turnover are important for proper plant growth and productivity. The glucose polymers that constitute the semi‐crystalline starch granule are synthesised by the concerted actions of well‐conserved classes of isoforms of starch synthase and starch‐branching enzyme, via a process that also requires the debranching enzyme isoamylase. The degradation of the granule proceeds via different pathways in different types of starch‐storing tissues. The pathway of starch degradation differs between different plant tissues, but has been elucidated in most detail in leaves. The polymer is first phosphorylated to allow access to the insoluble granule by enzymes that cleave bonds between glucose residues. The main product of this degradation is maltose, which is exported into the cytosol before a series of enzymatic steps convert it to sucrose. Key Concepts Starch is the main carbon store of most plants. It is a glucose polymer that is stored as insoluble granules within plastids. The polymer is composed of two fractions, branched amylopectin and unbranched amylose. It is synthesised by a number of enzymes that control the amount made, as well as the amounts of amylose and amylopectin. Starch is synthesised in leaves during the day and is mobilised at night. The rate of leaf starch degradation at night is closely controlled by mechanisms linked to the circadian clock so that starch is eliminated just before the beginning of day. Leaf starch degradation involves many enzymes that lead to the production of soluble sugars, mainly maltose. Maltose is exported into the cytosol where it is converted to sucrose. Arabidopsis plants in which starch metabolism is impaired grow poorly. Starch synthesised in leaves is often termed transitory starch, while that in storage organs can be termed storage starch. They are different in terms of the structure of the amylose and amylopectin within them.

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Identification of a Novel Enzyme Required for Starch Metabolism in Arabidopsis Leaves. The Phosphoglucan, Water Dikinase

Cited by 245 publications

References 36 publications

Glucan, water dikinase phosphorylates crystalline maltodextrins and thereby initiates solubilization

Glucan, water dikinase phosphorylates crystalline maltodextrins and thereby initiates solubilization

Plant α‐glucan phosphatases SEX4 and LSF2 display different affinity for amylopectin and amylose

Starch Biosynthesis and Degradation in Plants

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