study of the in-vitro regulation of phosphoenolpyruvate carboxylase from the epidermis of Commelina communis by malate and glucose-6-phosphate

Phosphoenolpyruvate (PEP) carboxylase activity in epidermal extracts of Commelina communis has been compared in the presence of malate and glucose-6-phosphate. The activity of PEP carboxylase was inhibited by increasing malate concentrations at several substrate (PEP) concentrations and changes in b...

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Bibliographic Details
Published in:Planta 1982-09, Vol.155 (5), p.416-422
Main Authors: Donkin, M.E, Taffs, J, Martin, E.S
Format: Article
Language:English
Subjects:
C4 plants
Enzyme activity
Enzymes
Epidermis
Guard cells
Kinetics
Outlawry
Physiological regulation
plant biochemistry
Plant epidermis
plant physiology
Plants
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Summary:Phosphoenolpyruvate (PEP) carboxylase activity in epidermal extracts of Commelina communis has been compared in the presence of malate and glucose-6-phosphate. The activity of PEP carboxylase was inhibited by increasing malate concentrations at several substrate (PEP) concentrations and changes in both the apparent Km (PEP) and Vmax values in the presence of malate suggested the occurence of mixed-type inhibiton. In the presence of glucose-6-phosphate no increase in enzyme activity was observed, although there was a slight decrease in the Km (PEP). However, glucose-6-phosphate appeared to alleviate the inhibition caused by malate. The possible implications of these properties in the control of malate production in guard cells is discussed.
ISSN:0032-0935
1432-2048
DOI:10.1007/BF00394470