TY  - JOUR
A1  - Malinova, Irina
A1  - Mahto, Harendra
A1  - Brandt, Felix
A1  - AL-Rawi, Shadha
A1  - Qasim, Hadeel
A1  - Brust, Henrike
A1  - Hejazi, Mahdi
A1  - Fettke, Jörg
T1  - EARLY STARVATION1 specifically affects the phosphorylation action of starch-related dikinases
JF  - The plant journal
N2  - 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.
KW  - Arabidopsis thaliana
KW  - EARLY STARVATION1
KW  - glucan
KW  - phosphoglucan
KW  - starch granule surface
KW  - starch phosphorylation
KW  - water dikinase
Y1  - 2018
U6  - https://doi.org/10.1111/tpj.13937
SN  - 0960-7412
SN  - 1365-313X
VL  - 95
IS  - 1
SP  - 126
EP  - 137
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Mahlow, Sebastian
A1  - Hejazi, Mahdi
A1  - Kuhnert, Franziska
A1  - Garz, Andreas
A1  - Brust, Henrike
A1  - Baumann, Otto
A1  - Fettke, Jörg
T1  - Phosphorylation of transitory starch by -glucan, water dikinase during starch turnover affects the surface properties and morphology of starch granules
JF  - New phytologist : international journal of plant science
N2  - 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.
KW  - Arabidopsis thaliana
KW  - glucan
KW  - water dikinase (GWD)
KW  - sex1-8
KW  - starch granule surface
KW  - starch phosphorylation
Y1  - 2014
U6  - https://doi.org/10.1111/nph.12801
SN  - 0028-646X
SN  - 1469-8137
VL  - 203
IS  - 2
SP  - 495
EP  - 507
PB  - Wiley-Blackwell
CY  - Hoboken
ER  -