1990
DOI: 10.1016/0014-5793(90)81267-r
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Sucrose‐phosphate synthase is dephosphorylated by protein phosphatase 2A in spinach leaves

Abstract: Sucrose-phosphate synthase (SPS) purified from spinach leaves harvested in the dark, was activated by mammalian protein phosphatase 2A (PPZA). Activation of SPS in a fraction from darkened spinach leaves was largely prevented by either okadaic acid or microcystin-LR (specific inhibitors of PPI and PP2A), while inhibitor-2 (a PPl inhibitor) or Mg2' (essential for PP2C) were ineffective. In vivo, okadaic acid and microcystin-LR prevented the light-induced activation of SPS and decreased sucrose biosynthesis and … Show more

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Cited by 124 publications
(86 citation statements)
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“…Immunolocalization shows that OA in P. lima occurs in peripheral chloroplasts and may be affiliated with hydrophobic membranes (Zhou and Fritz, 1994). This location is considered insensitive to OA since only trace amounts of PP-1 and PP-2A have been detected in chloroplasts and are therefore unlikely to be directly involved in regulating chloroplast metabolism (Siegl et al, 1990). One explanation for the lack of autotoxicity is that OA is sequestered away from the major phosphatase pool.…”
Section: Okadaic Acidmentioning
confidence: 99%
“…Immunolocalization shows that OA in P. lima occurs in peripheral chloroplasts and may be affiliated with hydrophobic membranes (Zhou and Fritz, 1994). This location is considered insensitive to OA since only trace amounts of PP-1 and PP-2A have been detected in chloroplasts and are therefore unlikely to be directly involved in regulating chloroplast metabolism (Siegl et al, 1990). One explanation for the lack of autotoxicity is that OA is sequestered away from the major phosphatase pool.…”
Section: Okadaic Acidmentioning
confidence: 99%
“…Phosphorylation and depho.sphorylation occur within 10-15 min, and alter the kinetic properties of the enzyme. Phosphorylation leads to a lowering of the substrate affinity of the enzyme, and makes it more susceptible to inhibition by Pj and more dependent on Glc6P Siegl, Mackintosh & Stitt 1990). Reversible phosphorylation is involved in the regulation of SPS in response to rising rates of photosynthesis (Stitt et al 1988), accumulation of sucrose (Stitt et al 1988), the assimilation of nitrate (Van Quy & Champigny 1992) and water stress (Quick et al 1989;Zrenner & Stitt 1991;, although all the details of the regulation circuits have not yet been elucidated (see Huber & Huber 1996).…”
Section: Introductionmentioning
confidence: 99%
“…One example of this effect was a decrease in the activities of phosphatase proteins 1 (PP1) and 2A (PP2A) in Brassica napus L. when exposed to MC-LR (Mackintosh et al, 1990). There was also a reduction in the activity of the enzyme sucrose-phosphate synthase resulting from the inhibition of PP1 and PP2A by okadaic acid and MC-LR in leaves of Spinacia oleracea L., both in vitro and in vivo, causing a decrease in the biosynthesis of sucrose and the fixation of carbon dioxide (Siegl et al, 1990).…”
Section: Diverse Effects Of Microcystins On Terrestrial Plantsmentioning
confidence: 99%
“…The MCs are potent inhibitors of phosphatases of the serine/threonine protein 1 (PP1) and 2A (PP2A) (Mackintosh et al, 1990). Because these phosphatases are involved in the functional dynamics of hepatocystic cytoskeletons, their inhibition causes a disarrangement of the cell cytoskeleton, causing the death of these cells, leading to intrahepatic hemorrhage and sometimes causing death (Carmichael, 1992;Mackintosh et al, 1990;Wickstrom et al, 1995).…”
Section: Introductionmentioning
confidence: 99%
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