title: Similar protein phosphatases control starch metabolism in plants and glycogen metabolism in mammals.
abstract: We report that protein phosphorylation is involved in the control of starch metabolism in Arabidopsis leaves at night. sex4 (starch excess 4) mutants, which have strongly reduced rates of starch metabolism, lack a protein predicted to be a dual specificity protein phosphatase. We have shown that this protein is chloroplastic and can bind to glucans and have presented evidence that it acts to regulate the initial steps of starch degradation at the granule surface. Remarkably, the most closely related protein to SEX4 outside the plant kingdom is laforin, a glucan-binding protein phosphatase required for the metabolism of the mammalian storage carbohydrate glycogen and implicated in a severe form of epilepsy (Lafora disease) in humans.
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
authors.forename: Totte
authors.initials: T
authors.lastname: Niittylä
authors.forename: Sylviane
authors.initials: S
authors.lastname: Comparot-Moss
authors.forename: Wei-Ling
authors.initials: WL
authors.lastname: Lue
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Messerli
authors.forename: Martine
authors.initials: M
authors.lastname: Trevisan
authors.forename: Michael D J
authors.initials: MD
authors.lastname: Seymour
authors.forename: John A
authors.initials: JA
authors.lastname: Gatehouse
authors.forename: Dorthe
authors.initials: D
authors.lastname: Villadsen
authors.forename: Steven M
authors.initials: SM
authors.lastname: Smith
authors.forename: Jychian
authors.initials: J
authors.lastname: Chen
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Zeeman
authors.forename: Alison M
authors.initials: AM
authors.lastname: Smith
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000737:chemistry; D005936:Glucans / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism*; D006801:Humans; D008322:Mammals / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D018515:Plant Leaves / Q000737:chemistry / Q000166:cytology; D013213:Starch / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D005936:Glucans; D013213:Starch; D006003:Glycogen; D010749:Phosphoprotein Phosphatases