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Regulation of Phosphoenolpyruvate Carboxylase in Zea mays by Protein Phosphorylation and Metabolites and Their Roles in Photosynthesis

Gao, Yu and Woo, K. C. (1996). Regulation of Phosphoenolpyruvate Carboxylase in Zea mays by Protein Phosphorylation and Metabolites and Their Roles in Photosynthesis. Australian Journal of Plant Physiology,23(1):25-32.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 17 times in Scopus Article | Citations

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Title Regulation of Phosphoenolpyruvate Carboxylase in Zea mays by Protein Phosphorylation and Metabolites and Their Roles in Photosynthesis
Author Gao, Yu
Woo, K. C.
Journal Name Australian Journal of Plant Physiology
Publication Date 1996
Volume Number 23
Issue Number 1
ISSN 0310-7841   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-0030037958
Start Page 25
End Page 32
Total Pages 8
Place of Publication Australia
Publisher C S I R O Publishing
Field of Research 0607 - Plant Biology
Abstract The effects of metabolites, protein phosphorylation and malate inhibition on phosphoenolpyruvate carboxylase (PEPC) activity were investigated at pH 7.0 in partially purified enzyme from maize leaves. Glycine, glucose 6-phosphate or alanine stimulated the activity two- to three-fold. Glycine and glucose 6-phosphate increased the affinity for PEP by factors of eight and four respectively. These metabolites changed the response of the enzyme activity to pH. Activity increased between pH 6.8 and 8.0 by 10-fold in the absence and 26% in the presence of these metabolites. In vitro phosphorylation of PEPC increased the activity two-fold in the absence but not in the presence of these metabolites. Malate was a strong inhibitor of PEPC, the KI value being 0.25-0.5 mM. Protein phosphorylation and the above metabolites increased the Ki value by factors of three and 12 respectively, but they synergistically increased the Ki 50-fold, thus providing maximal protection against malate inhibition. In the crude extracts from light- and dark-adapted leaves in the presence of a physiological concentration of malate (20 mM), PEPC activity comparable to the photosynthetic rate was obtained only from the light-adapted leaves in the presence of metabolites indicating that both light-induced protein phosphorylation and metabolic activators were essential for PEPC activation during photosynthesis. We propose that both these factors act synergistically to modulate PEPC during photosynthesis in maize.
DOI http://dx.doi.org/10.1071/PP9960025   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
Additional Notes Since January 2002: Functional Plant Biology, ISSN: 1445-4408
 
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Created: Fri, 29 Aug 2014, 20:15:48 CST by Anthony Hornby