@article{DeschampsHaferkampDauvilleeetal.2006,
  author    = {Deschamps, Philippe and Haferkamp, Ilka and Dauvillee, David and Haebel, Sophie and Steup, Martin and Buleon, Alain and Putaux, Jean-Luc and Colleoni, Christophe and d'Hulst, Christophe and Plancke, Charlotte and Gould, Sven and Maier, Uwe and Neuhaus, Heinz Eckhard and Ball, Steven G.},
  title     = {Nature of the periplastidial pathway of starch synthesis in the cryptophyte Guillardia theta},
  issn      = {1535-9778},
  doi       = {10.1128/Ec.00380-05},
  year      = {2006},
  abstract  = {The nature of the periplastidial pathway of starch biosynthesis was investigated with the model cryptophyte Guillardia theta. The storage polysaccharide granules were shown to be composed of both amylose and amylopectin fractions with a chain length distribution and crystalline organization very similar to those of starch from green algae and land plants. Most starch granules displayed a shape consistent with biosynthesis occurring around the pyrenoid through the rhodoplast membranes. A protein with significant similarity to the amylose-synthesizing granule-bound starch syntbase 1 from green plants was found as the major polypeptide bound to the polysaccharide matrix. N-terminal sequencing of the mature protein proved that the precursor protein carries a nonfunctional transit peptide in its bipartite topogenic signal sequence which is cleaved without yielding transport of the enzyme across the two inner plastid membranes. The enzyme was shown to display similar affinities for ADP and UDP-glucose, while the V-max measured with UDP-glucose was twofold higher. The granule-bound starch synthase from Guillardia theta was demonstrated to be responsible for the synthesis of long glucan chains and therefore to be the functional equivalent of the amylose- synthesizing enzyme of green plants. Preliminary characterization of the starch pathway suggests that Guillardia theta utilizes a UDP-glucose-based pathway to synthesize starch},
  language  = {en}
}
@article{DuwenigSteupKossmann1997,
  author    = {Duwenig, Elke and Steup, Martin and Kossmann, Jens},
  title     = {Induction of genes encoding plastidic phosphorylase from spinach (Spinacia oleracea L.) and potato (Solanum tuberosum L.) by exogenously supplied carbohydrates in excised leaf discs},
  year      = {1997},
  language  = {en}
}
@article{DuwenigSteupWillmitzeretal.1997,
  author    = {Duwenig, Elke and Steup, Martin and Willmitzer, Lothar and Kossmann, Jens},
  title     = {Antisense inhibition of cytosolic phosphorylase in potato plants (Solanum tuberosum L.) affects tuber sprouting and flower formation with only little impact on carbohydrate metabolism},
  year      = {1997},
  language  = {en}
}
@inproceedings{EbenhoehKartalSkupinetal.2013,
  author    = {Ebenh{\"o}h, O. and Kartal, Oe. and Skupin, A. and Mahlow, S. and Steup, Martin},
  title     = {The role of mixing entropy in carbohydrate metabolism},
  series = {European biophysics journal : with biophysics letters ; an international journal of biophysics},
  volume    = {42},
  booktitle = {European biophysics journal : with biophysics letters ; an international journal of biophysics},
  publisher = {Springer},
  address   = {New York},
  issn      = {0175-7571},
  pages     = {S73 -- S73},
  year      = {2013},
  language  = {en}
}
@article{EckermannFettkePaulyetal.2004,
  author    = {Eckermann, Nora and Fettke, J{\"o}rg and Pauly, Markus and Bazant, Esther and Steup, Martin},
  title     = {Starch-metabolism related isozymes in higher plants},
  year      = {2004},
  language  = {en}
}
@article{EckermannFettkeSteup2002,
  author    = {Eckermann, Nora and Fettke, J{\"o}rg and Steup, Martin},
  title     = {Identification of polysaccharide binding proteins by affinity electrophoresis in inhomogeneous polyacrylamide gels and subsequent SDS-PAGE/MALDI-TOF analysis},
  year      = {2002},
  language  = {en}
}
@article{FettkeAlbrechtHejazietal.2010,
  author    = {Fettke, J{\"o}rg and Albrecht, Tanja and Hejazi, Mahdi and Mahlow, Sebastian and Nakamura, Yasunori and Steup, Martin},
  title     = {Glucose 1-phosphate is efficiently taken up by potato (Solanum tuberosum) tuber parenchyma cells and converted to reserve starch granules},
  issn      = {0028-646X},
  doi       = {10.1111/j.1469-8137.2009.03126.x},
  year      = {2010},
  abstract  = {Reserve starch is an important plant product but the actual biosynthetic process is not yet fully understood. Potato (Solanum tuberosum) tuber discs from various transgenic plants were used to analyse the conversion of external sugars or sugar derivatives to starch. By using in vitro assays, a direct glucosyl transfer from glucose 1-phosphate to native starch granules as mediated by recombinant plastidial phosphorylase was analysed. Compared with labelled glucose, glucose 6-phosphate or sucrose, tuber discs converted externally supplied [C-14] glucose 1-phosphate into starch at a much higher rate. Likewise, tuber discs from transgenic lines with a strongly reduced expression of cytosolic phosphoglucomutase, phosphorylase or transglucosidase converted glucose 1-phosphate to starch with the same or even an increased rate compared with the wild-type. Similar results were obtained with transgenic potato lines possessing a strongly reduced activity of both the cytosolic and the plastidial phosphoglucomutase. Starch labelling was, however, significantly diminished in transgenic lines, with a reduced concentration of the plastidial phosphorylase isozymes. Two distinct paths of reserve starch biosynthesis are proposed that explain, at a biochemical level, the phenotype of several transgenic plant lines.},
  language  = {en}
}
@article{FettkeChiaEckermannetal.2006,
  author    = {Fettke, J{\"o}rg and Chia, Tansy and Eckermann, Nora and Smith, Alison M. and Steup, Martin},
  title     = {A transglucosidase necessary for starch degradation and maltose metabolism in leaves at night acts on cytosolic heteroglycans (SHG)},
  issn      = {0960-7412},
  doi       = {10.1111/j.1365-313X.2006.02732.x},
  year      = {2006},
  abstract  = {The recently characterized cytosolic transglucosidase DPE2 (EC 2.4.1.25) is essential for the cytosolic metabolism of maltose, an intermediate on the pathway by which starch is converted to sucrose at night. In in vitro assays, the enzyme utilizes glycogen as a glucosyl acceptor but the in vivo acceptor molecules remained unknown. In this communication we present evidence that DPE2 acts on the recently identified cytosolic water-soluble heteroglycans (SHG) as does the cytosolic phosphorylase (EC 2.4.1.1) isoform. By using in vitro two-step C-14 labeling assays we demonstrate that the two transferases can utilize the same acceptor sites of the SHG. Cytosolic heteroglycans from a DPE2-deficient Arabidopsis mutant were characterized. Compared with the wild type the glucose content of the heteroglycans was increased. Most of the additional glucosyl residues were found in the outer chains of SHG that are released by an endo- alpha-arabinanase (EC 3.2.1.99). Additional starch-related mutants were characterized for further analysis of the increased glucosyl content. Based on these data, the cytosolic metabolism of starch-derived carbohydrates is discussed},
  language  = {en}
}
@article{FettkeEckermannPoesteetal.2004,
  author    = {Fettke, J{\"o}rg and Eckermann, Nora and Poeste, Simon and Steup, Martin},
  title     = {The glycan substrate of the cytosolic (Pho 2) phosphorylase isozyme from Pisum sativum L. : identification, linkage analysis and subcellular localization},
  issn      = {0960-7412},
  year      = {2004},
  abstract  = {The subcellular distribution of starch-related enzymes and the phenotype of Arabidopsis mutants defective in starch degradation suggest that the plastidial starch turnover is linked to a cytosolic glycan metabolism. In this communication, a soluble heteroglycan (SHG) from leaves of Pisum sativum L. has been studied. Major constituents of the SHG are galactose, arabinose and glucose. For subcellular location, the SHG was prepared from isolated protoplasts and chloroplasts. On a chlorophyll basis, protoplasts and chloroplasts yielded approximately 70\% and less than 5\%, respectively, of the amount of the leaf-derived SHG preparation. Thus, most of SHG resides inside the cell but outside the chloroplast. SHG is soluble and not membrane-associated. Using membrane filtration, the SHG was separated into a <10 kDa and a >10 kDa fraction. The latter was resolved into two subfractions (I and II) by field-flow fractionation. In the protoplast-derived >10 kDa SHG preparation the subfraction I was by far the most dominant compound. beta-Glucosyl Yariv reagent was reactive with subfraction II, but not with subfraction I. In in vitro assays the latter acted as glucosyl acceptor for the cytosolic (Pho 2) phosphorylase but not for rabbit muscle phosphorylase. Glycosidic linkage analyses of subfractions I and II and of the Yariv reagent reactive glycans revealed that all three glycans contain a high percentage of arabinogalactan-like linkages. However, SHG possesses a higher content of minor compounds, namely glucosyl, mannosyl, rhamnosyl and fucosyl residues. Based on glycosyl residues and glycosidic linkages, subfraction I possesses a more complex structure than subfraction II},
  language  = {en}
}
@article{FettkeEckermannTiessenetal.2005,
  author    = {Fettke, J{\"o}rg and Eckermann, Nora and Tiessen, Axel and Geigenberger, Peter Ludwig and Steup, Martin},
  title     = {Identification, subcellular localization and biochemical characterization of water-soluble heteroglycans (SHG) in leaves of Arabidopsis thaliana L. : distinct SHG reside in the cytosol and in the apoplast},
  issn      = {0960-7412},
  year      = {2005},
  abstract  = {Water-soluble heteroglycans (SHG) were isolated from leaves of wild-type Arabidopsis thaliana L. and from two starch-deficient mutants. Major constituents of the SHG are arabinose, galactose, rhamnose, and glucose. SHG was separated into low (< 10 kDa; SHG(S)) and high (> 10 kDa; SHG(L)) molecular weight compounds. SHG(S) was resolved into approximately 25 distinct oligoglycans by ion exchange chromatography. SHG(L) was further separated into two subfractions, designated as subfraction I and II, by field flow fractionation. For the intracellular localization of the various SHG compounds several approaches were chosen: first, leaf material was subjected to non-aqueous fractionation. The apolar gradient fractions were characterized by monitoring markers and were used as starting material for the SHG isolation. Subfraction I and SHG(S) exhibited a distribution similar to that of cytosolic markers whereas subfraction II cofractionated with crystalline cellulose. Secondly, intact organelles were isolated and used for SHG isolation. Preparations of intact organelles (mitochondria plus peroxisomes) contained no significant amount of any heteroglycan. In isolated intact microsomes a series of oligoglycans was recovered but neither subfraction I nor II. In in vitro assays using glucose 1-phosphate and recombinant cytosolic (Pho 2) phosphorylase both SHG(S) and subfraction I acted as glucosyl acceptor whereas subfraction II was essentially inactive. Rabbit muscle phosphorylase a did not utilize any of the plant glycans indicating a specific Pho 2-glycan interaction. As revealed by in vivo labeling experiments using (CO2)-C-14 carbon fluxes into subfraction I and II differed. Furthermore, in leaves the pool size of subfraction I varied during the light-dark regime},
  language  = {en}
}