Open AccessRole of Magnesium in the Binding of Substrate and Effectors to Phosphoenolpyruvate Carboxylase from a CAM Plant
Author(s) -
Randolph T. Wedding,
M. Black
Publication year - 1988
Publication title -
plant physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.87.2.443
Subject(s) - phosphoenolpyruvate carboxylase , phosphoenolpyruvate carboxykinase , biochemistry , enzyme , substrate (aquarium) , magnesium , binding site , chemistry , tryptophan , pyruvate carboxylase , biology , amino acid , organic chemistry , ecology
The binding of phosphoenolpyruvate, malate, and glucose 6-phosphate to phosphoenolpyruvate carboxylase purified from Crassula argentea Thunb. was measured using both the intrinsic tryptophan fluorescence of the enzyme and the extrinsic fluorescence of the complex of 8-anilino-1-napthalenesulfonate with the enzyme. It was found that the substrate phosphoenolpyruvate can bind in the absence of magnesium but is bound in greater quantities and more tightly when magnesium is present. Malate reduces the binding of phosphoenolpyruvate, while glucose 6-phosphate increases the binding of the substrate. Glucose 6-phosphate requires magnesium to bind to the enzyme, while malate does not. The general trends from the binding experiments using fluorescence methods were confirmed by activity determinations using assays performed in the absence of magnesium.