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Metabolite Regulation of Phosphenolpyruvate Carboxylase in Legume Root Nodules

Woo, K. C. and Xu, Shoumin (1996). Metabolite Regulation of Phosphenolpyruvate Carboxylase in Legume Root Nodules. Australian Journal of Plant Physiology,23(4):413-419.

Document type: Journal Article
Citation counts: Scopus Citation Count Cited 2 times in Scopus Article | Citations

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Title Metabolite Regulation of Phosphenolpyruvate Carboxylase in Legume Root Nodules
Author Woo, K. C.
Xu, Shoumin
Journal Name Australian Journal of Plant Physiology
Publication Date 1996
Volume Number 23
Issue Number 4
ISSN 0310-7841   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-0029738402
Start Page 413
End Page 419
Total Pages 7
Place of Publication Australia
Publisher C S I R O Publishing
Field of Research 0607 - Plant Biology
Abstract The effects of metabolic activators and inhibitors on phosphoenolpyruvate carboxylase (PEPC) activity were examined at pH 7 in partially purified enzyme from nodules of soybean (Glycine max (L.) Merr.), Psophocarpus tetragonolobus DC. and Vigna unguiculata ssp. sesquipedalis (L.) Verdc. Glucose 6-phosphate, fructose 6-phosphate, glucose 1-phosphate, fructose 1-phosphate, fructose 1,6- bisphosphate and phosphoglycerate stimulated the activity about 2-fold at low (0.5 mM) but not saturating (2.5 mM) PEP concentration. Glc 6-P and fru 6-P were the most effective activators and they increased the affinity of the enzyme for PEP by 2-4-fold. The dicarboxylates, malate, succinate, malonate, 2-oxoglutarate and aspartate inhibited PEPC activity. Malate was the most inhibitory, and strongly inhibited PEPC activity even at saturating PEP concentration. The Ki values for malate were 0.3-0.4 mM for soybean and P. tetragonolobus. However, glc 6-P and fru 6-P alleviated maiate inhibition and increased the Ki values by 11- to 28-fold in these two species. We propose that glc 6-P (fru 6-P) activates PEPC in a feedforward regulation and protects it against feedback inhibition by malate and thus coordinates the supply of photosynthate availability with malate synthesis required by the bacteroids to support symbiotic nitrogen fixation in nodules.
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Created: Fri, 29 Aug 2014, 20:19:14 CST by Anthony Hornby