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Photosynthesis Research

, Volume 16, Issue 3, pp 233–242 | Cite as

Effects of temperature and photosynthetic inhibitors on light activation of C4-phosphoenolpyruvate carboxylase

  • Y. Samaras
  • Y. Manetas
  • N. A. Gavalas
Regular Papers

Abstract

Phosphoenolpyruvate carboxylase from leaves of the C4 plant Setaria verticillata (L.) Beauv. is activated by light; day levels of activity are reached after 30 minutes of illumination. Photoactivation is prevented by inhibitors of photosynthetic electron flow or of photophosphorylation and by D,L-glyceraldehyde, which inhibits the reductive pentose phosphate pathway.

Although the extractable activity in the dark is not affected by temperature the photoactivation is prevented when both illumination and extraction are done under low temperature (5 C). High temperature (30 C) during either illumination or extraction is needed for activation. Once the enzyme is photoactivated at 30 C, a transfer of the leaves to 5 C does not abolish the extra activity.

The results suggest that both unimpaired electron flow and photophosphorylation are prerequisites for the activation of phosphoenolpyruvate carboxylase. Low temperature apparently suppresses either the transport to the cytoplasm of a photosynthetic intermediate or the activating reaction itself. The inclusion of phosphoenolpyruvate in the extraction medium increases the night activity.

On the basis of the available information, it is suggested that phosphoenolpyruvate could be the activator in vivo. In that case, the activation of phosphoenolpyruvate carboxylase would depend on internal CO2 level and prior photoactivation of both pyruvate, orthophosphate, dikinase and NADP malate dehydrogenase.

Key words

light activation PEPCase photosynthetic inhibitors Setaria verticillata (L.) Beauv. temperature 

Abbreviations

PEPCase

phosphoenolpyruvate carboxylase

PEP

phosphoenolpyruvate

PAR

photosynthetically active radiation

CCCP

carbonyl cyanide m-chlorophenylhydrazone

DCMU

3-(3, 4-dichlorophenyl)-1, 1-dimethylurea

DSPD

disalicylidenpropanediamine

MV

methylviologen

ME

malic enzyme

MDH

malate dehydrogenase

PPDK

pyruvate, Pi dikinase

CAM

Crassulacean Acid Metabolism

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Copyright information

© Kluwer Academic Publishers 1988

Authors and Affiliations

  • Y. Samaras
    • 1
  • Y. Manetas
    • 1
  • N. A. Gavalas
    • 1
  1. 1.Laboratory of Plant Physiology, Department of BiologyUniversity of PatrasPatrasGreece

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