@article{MalinovaMahtoBrandtetal.2018,
  author    = {Malinova, Irina and Mahto, Harendra and Brandt, Felix and AL-Rawi, Shadha and Qasim, Hadeel and Brust, Henrike and Hejazi, Mahdi and Fettke, J{\"o}rg},
  title     = {EARLY STARVATION1 specifically affects the phosphorylation action of starch-related dikinases},
  series = {The plant journal},
  volume    = {95},
  journal   = {The plant journal},
  number    = {1},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0960-7412},
  doi       = {10.1111/tpj.13937},
  pages     = {126 -- 137},
  year      = {2018},
  abstract  = {Starch phosphorylation by starch-related dikinases glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) is a key step in starch degradation. Little information is known about the precise structure of the glucan substrate utilized by the dikinases and about the mechanisms by which these structures may be influenced. A 50-kDa starch-binding protein named EARLY STARVATION1 (ESV1) was analyzed regarding its impact on starch phosphorylation. In various invitro assays, the influences of the recombinant protein ESV1 on the actions of GWD and PWD on the surfaces of native starch granules were analyzed. In addition, we included starches from various sources as well as truncated forms of GWD. ESV1 preferentially binds to highly ordered, -glucans, such as starch and crystalline maltodextrins. Furthermore, ESV1 specifically influences the action of GWD and PWD at the starch granule surface. Starch phosphorylation by GWD is decreased in the presence of ESV1, whereas the action of PWD increases in the presence of ESV1. The unique alterations observed in starch phosphorylation by the two dikinases are discussed in regard to altered glucan structures at the starch granule surface.},
  language  = {en}
}
@article{RitteHeydenreichMahlowetal.2006,
  author    = {Ritte, Gerhard and Heydenreich, Matthias and Mahlow, Sebastian and Haebel, Sophie and Koetting, Oliver and Steup, Martin},
  title     = {Phosphorylation of C6- and C3-positions of glucosyl residues in starch is catalysed by distinct dikinases},
  series = {FEBS letters : the journal for rapid publication of short reports in molecular biosciences},
  volume    = {580},
  journal   = {FEBS letters : the journal for rapid publication of short reports in molecular biosciences},
  number    = {20},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0014-5793},
  doi       = {10.1016/j.febslet.2006.07.085},
  pages     = {4872 -- 4876},
  year      = {2006},
  abstract  = {Glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) are required for normal starch metabolism. We analysed starch phosphorylation in Arabidopsis wildtype plants and mutants lacking either GWD or PWD using P-31 NMR. Phosphorylation at both C6- and C3-positions of glucose moieties in starch was drastically decreased in GWD-deficient mutants. In starch from PWD-deficient plants C3-bound phosphate was reduced to levels close to the detection limit. The latter result contrasts with previous reports according to which GWD phosphorylates both C6- and C3-positions. In these studies, phosphorylation had been analysed by HPLC of acid-hydrolysed glucans. We now show that maltose-6-phosphate, a product of incomplete starch hydrolysis, co-eluted with glucose-3-phosphate under the chromatographic conditions applied. Re-examination of the specificity of the dikinases using an improved method demonstrates that C6- and C3-phosphorylation is selectively catalysed by GWD and PWD, respectively.},
  language  = {en}
}
@article{MahlowHejaziKuhnertetal.2014,
  author    = {Mahlow, Sebastian and Hejazi, Mahdi and Kuhnert, Franziska and Garz, Andreas and Brust, Henrike and Baumann, Otto and Fettke, J{\"o}rg},
  title     = {Phosphorylation of transitory starch by -glucan, water dikinase during starch turnover affects the surface properties and morphology of starch granules},
  series = {New phytologist : international journal of plant science},
  volume    = {203},
  journal   = {New phytologist : international journal of plant science},
  number    = {2},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0028-646X},
  doi       = {10.1111/nph.12801},
  pages     = {495 -- 507},
  year      = {2014},
  abstract  = {Glucan, water dikinase (GWD) is a key enzyme of starch metabolism but the physico-chemical properties of starches isolated from GWD-deficient plants and their implications for starch metabolism have so far not been described. Transgenic Arabidopsis thaliana plants with reduced or no GWD activity were used to investigate the properties of starch granules. In addition, using various in vitro assays, the action of recombinant GWD, -amylase, isoamylase and starch synthase 1 on the surface of native starch granules was analysed. The internal structure of granules isolated from GWD mutant plants is unaffected, as thermal stability, allomorph, chain length distribution and density of starch granules were similar to wild-type. However, short glucan chain residues located at the granule surface dominate in starches of transgenic plants and impede GWD activity. A similarly reduced rate of phosphorylation by GWD was also observed in potato tuber starch fractions that differ in the proportion of accessible glucan chain residues at the granule surface. A model is proposed to explain the characteristic morphology of starch granules observed in GWD transgenic plants. The model postulates that the occupancy rate of single glucan chains at the granule surface limits accessibility to starch-related enzymes.},
  language  = {en}
}
@article{HejaziSteupFettke2012,
  author    = {Hejazi, Mahdi and Steup, Martin and Fettke, J{\"o}rg},
  title     = {The plastidial glucan, water dikinase (GWD) catalyses multiple phosphotransfer reactions},
  series = {The FEBS journal},
  volume    = {279},
  journal   = {The FEBS journal},
  number    = {11},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1742-464X},
  doi       = {10.1111/j.1742-4658.2012.08576.x},
  pages     = {1953 -- 1966},
  year      = {2012},
  abstract  = {The plant genome encodes at least two distinct and evolutionary conserved plastidial starch-related dikinases that phosphorylate a low percentage of glucosyl residues at the starch granule surface. Esterification of starch favours the transition of highly ordered a-glucans to a less ordered state and thereby facilitates the cleavage of interglucose bonds by hydrolases. Metabolically most important is the phosphorylation at position C6, which is catalysed by the glucan, water dikinase (GWD). The reactions mediated by recombinant wild-type GWD from Arabidopsis thaliana (AtGWD) and from Solanum tuberosum (StGWD) were studied. Two mutated proteins lacking the conserved histidine residue that is indispensible for glucan phosphorylation were also included. The wild-type GWDs consume approximately 20\% more ATP than is required for glucan phosphorylation. Similarly, although incapable of phosphorylating a-glucans, the two mutated dikinase proteins are capable of degrading ATP. Thus, consumption of ATP and phosphorylation of a-glucans are not strictly coupled processes but, to some extent, occur as independent phosphotransfer reactions. As revealed by incubation of the GWDs with [gamma-33P]ATP, the consumption of ATP includes the transfer of the gamma-phosphate group to the GWD protein but this autophosphorylation does not require the conserved histidine residue. Thus, the GWD proteins possess two vicinal phosphorylation sites, both of which are transiently phosphorylated. Following autophosphorylation at both sites, native dikinases flexibly use various terminal phosphate acceptors, such as water, alpha-glucans, AMP and ADP. A model is presented describing the complex phosphotransfer reactions of GWDs as affected by the availability of the various acceptors.},
  language  = {en}
}