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Sucrose‐phosphate synthase is dephosphorylated by protein phosphatase 2A in spinach leaves
Author(s) -
Siegl Gabriele,
MacKintosh Carol,
Stitt Mark
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)81267-r
Subject(s) - okadaic acid , spinach , protein phosphatase 2 , phosphatase , sucrose phosphate synthase , biochemistry , phosphorylation , phosphate , in vivo , chemistry , sucrose , biology , sucrose synthase , microbiology and biotechnology , invertase
Sucrose‐phosphate synthase (SPS) purified from spinach leaves harvested in the dark, was activated by mammalian protein phosphatase 2A (PP2A). Activation of SPS in a fraction from darkened spinach leaves was largely prevented by either okadaic acid or microcystin‐LR (specific inhibitors of PP1 and PP2A), while inhibitor‐2 (a PP1 inhibitor) or Mg 2+ (essential for PP2C) were ineffective. In vivo, okadaic add and microcystin‐LR prevented the light‐induced activation of SPS and decreased sucrose biosynthesis and CO 2 fixation. It is concluded that PP2A is the major SPS phosphatase in spinach. This study is the first to employ microcystin‐LR for modulating protein phosphorylation in vivo.