RRC ID 15327
Author Santelia D, Kötting O, Seung D, Schubert M, Thalmann M, Bischof S, Meekins DA, Lutz A, Patron N, Gentry MS, Allain FH, Zeeman SC.
Title The phosphoglucan phosphatase like sex Four2 dephosphorylates starch at the C3-position in Arabidopsis.
Journal Plant Cell
Abstract Starch contains phosphate covalently bound to the C6-position (70 to 80% of total bound phosphate) and the C3-position (20 to 30%) of the glucosyl residues of the amylopectin fraction. In plants, the transient phosphorylation of starch renders the granule surface more accessible to glucan hydrolyzing enzymes and is required for proper starch degradation. Phosphate also confers desired properties to starch-derived pastes for industrial applications. In Arabidopsis thaliana, the removal of phosphate by the glucan phosphatase Starch Excess4 (SEX4) is essential for starch breakdown. We identified a homolog of SEX4, LSF2 (Like Sex Four2), as a novel enzyme involved in starch metabolism in Arabidopsis chloroplasts. Unlike SEX4, LSF2 does not have a carbohydrate binding module. Nevertheless, it binds to starch and specifically hydrolyzes phosphate from the C3-position. As a consequence, lsf2 mutant starch has elevated levels of C3-bound phosphate. SEX4 can release phosphate from both the C6- and the C3-positions, resulting in partial functional overlap with LSF2. However, compared with sex4 single mutants, the lsf2 sex4 double mutants have a more severe starch-excess phenotype, impaired growth, and a further change in the proportion of C3- and C6-bound phosphate. These findings significantly advance our understanding of the metabolism of phosphate in starch and provide innovative options for tailoring novel starches with improved functionality for industry.
Volume 23(11)
Pages 4096-111
Published 2011-11-1
DOI 10.1105/tpc.111.092155
PII tpc.111.092155
PMID 22100529
PMC PMC3246334
MeSH Amylopectin / metabolism Arabidopsis / genetics Arabidopsis / growth & development Arabidopsis / metabolism* Arabidopsis Proteins / chemistry Arabidopsis Proteins / genetics Arabidopsis Proteins / metabolism* Chloroplasts / metabolism Dual-Specificity Phosphatases / genetics Dual-Specificity Phosphatases / metabolism* Glucans / metabolism Models, Molecular Mutation Phenotype Phosphates / metabolism Protein Conformation Sequence Homology, Amino Acid Starch / chemistry Starch / metabolism* Substrate Specificity
IF 9.618
Times Cited 70
Arabidopsis / Cultured plant cells, genes pdx93940 pdy29091 pdy30584 pdz29685 pdz82152