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251384.0 [No comment] 16.10.2006 13:13 Released

ID: 251384.0, MPI für molekulare Pflanzenphysiologie / Publikationen Pflanzenphysiologie
Identification of a novel enzyme required for starch metabolism in Arabidopsis leaves. The phosphoglucan, water dikinase
Authors:Kotting, O.; Pusch, K.; Tiessen, A.; Geigenberger, P.; Steup, M.; Ritte, G.
Date of Publication (YYYY-MM-DD):2005-01
Title of Journal:Plant Physiology
Journal Abbrev.:Plant Physiol
Issue / Number:1
Start Page:242
End Page:252
Review Status:not specified
Audience:Not Specified
Abstract / Description:The phosphorylation of amylopectin by the glucan, water dikinase (GWD; EC is an essential step within starch metabolism. This is indicated by the starch excess phenotype of GWD-deficient plants, such as the sex1-3 mutant of Arabidopsis (Arabidopsis thaliana). To identify starch-related enzymes that rely on glucan-bound phosphate, we studied the binding of proteins extracted from Arabidopsis wild-type leaves to either phosphorylated or nonphosphorylated starch granules. Granules prepared from the sex1-3 mutant were prephosphorylated in vitro using recombinant potato (Solanum tuberosum) GWD. As a control, the unmodified, phosphate free granules were used. An as-yet uncharacterized protein was identified that preferentially binds to the phosphorylated starch. The C-terminal part of this protein exhibits similarity to that of GWD. The novel protein phosphorylates starch granules, but only following prephosphorylation with GWD. The enzyme transfers the beta-P of ATP to the phosphoglucan, whereas the gamma-P is released as orthophosphate. Therefore, the novel protein is designated as phosphoglucan, water dikinase (PWD). Unlike GWD that phosphorylates preferentially the C6 position of the glucose units, PWD phosphorylates predominantly (or exclusively) the C3 position. Western-blot analysis of protoplast and chloroplast fractions from Arabidopsis leaves reveals a plastidic location of PWD. Binding of PWD to starch granules strongly increases during net starch breakdown. Transgenic Arabidopsis plants in which the expression of PWD was reduced by either RNAi or a T-DNA insertion exhibit a starch excess phenotype. Thus, in Arabidopsis leaves starch turnover requires a close collaboration of PWD and GWD.
Free Keywords:r1 protein
; phosphorylating enzyme
; glucose 3-phosphate
; transitory starch
; potato-tubers
; plant genome
; phosphate
; degradation
; biosynthesis
; hydrolysis
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für molekulare Pflanzenphysiologie/Metabolische Netzwerke
External Affiliations:Univ Potsdam, Inst Biochem & Biol, D-14476 Golm, Germany
Univ Potsdam, Inst Biochem & Biol, D-14476 Golm, Germany
Max Planck Inst Mol Plant Physiol, D-14476 Golm, Germany
Identifiers:ISI:000226613100022 [ID No:1]
ISI:000226613100022 [ID No:2]