Involvement of thiol groups in the activity of phosphoenolpyruvate carboxylase from maize leaves

1984 ◽  
Vol 5 (3) ◽  
pp. 215-226 ◽  
Author(s):  
Alberto A. Iglesias ◽  
Carlos S. Andreo
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Thiol Groups ◽  
Maize Leaves

Response of Phosphoenolpyruvate Carboxylase from Maize Leaves to Moderate Water Deficit

1999 ◽  
Vol 155 (4-5) ◽  
pp. 631-638 ◽  
Author(s):  
Mireya Rodríguez-Penagos ◽  
Rosario A. Muñoz-Clares
Keyword(s):  
Water Deficit ◽  
Phosphoenolpyruvate Carboxylase ◽  
Maize Leaves

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

1996 ◽  
Vol 23 (1) ◽  
pp. 25 ◽  
Author(s):  
Y Gao ◽  
KC Woo
Keyword(s):  
Zea Mays ◽  
Enzyme Activity ◽  
Protein Phosphorylation ◽  
Photosynthetic Rate ◽  
Phosphoenolpyruvate Carboxylase ◽  
Strong Inhibitor ◽  
Physiological Concentration ◽  
Crude Extracts ◽  
Maize Leaves

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.

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