Determination of the starch-phosphorylating enzyme activity in plant extracts

Planta. 2003 Mar;216(5):798-801. doi: 10.1007/s00425-002-0931-1. Epub 2002 Nov 9.


For quantification of alpha-glucan, water dikinase (GWD) activity in crude extracts of plant tissues a radio-labeling assay was established that uses soluble starch and (33)P-labeled ATP as phosphate acceptor and donor, respectively. A constant rate of starch labeling was observed only if the ATP applied was labeled at the beta position. In wild-type extracts from leaves of Arabidopsis thaliana (L.) Heynh. the maximum rate of starch phosphorylation was approximately 27 pmol min(-1) (mg protein)(-1). Leaf extracts from the GWD-deficient sex1 mutants of Arabidopsis showed no significant incorporation of phosphate whereas extracts from potato (Solanum tuberosum L.) tuber expressing a GWD antisense construct exhibited less activity than the wild-type control. To our knowledge this is the first time that a quantification of the starch-phosphorylating activity has been achieved in plant crude extracts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Arabidopsis / enzymology*
  • Arabidopsis Proteins / metabolism
  • Glucans / metabolism
  • Monosaccharide Transport Proteins / metabolism
  • Phosphorus Radioisotopes
  • Plant Extracts / isolation & purification
  • Plant Extracts / metabolism*
  • Plant Leaves / enzymology
  • Solanum tuberosum / enzymology*
  • Starch / metabolism*
  • Starch Phosphorylase / metabolism*


  • Arabidopsis Proteins
  • Glucans
  • Monosaccharide Transport Proteins
  • Phosphorus Radioisotopes
  • Plant Extracts
  • Adenosine Triphosphate
  • Starch
  • Starch Phosphorylase
  • SEX1 protein, Arabidopsis