A fluorescence study of the effects of pH and Mg2+ on the conformation of fructose 1,6-diphosphatase from spinach chloroplasts.
2-p-Toluidino-naphthalene-6-sulfonate is a sensitive fluorescent reporter group which can be used for the detection of the conformation of fructose 1,6-diphosphatase from spinach chloroplasts. When fructose 1,6-diphosphatase was added to a dilute solution of 2-p-toluidino-naphthalene-6-sulfonate at pH 9.0, the fluorescence intensity gradually increased. At this pH, the enzyme activity decreased at the same rate. However, at neutral pH (7.5), this time-dependent fluorescence change was not observed. In the presence of Mg2+, which is an activator of the enzyme, the fluorescence intensity was increased instantly and did not change for 30 min in the pH range 8.0--9.0. From the concentration dependence of the fluorescence intensity, the dissociation constant for Mg2+ was determined, Kdis = 3 mM. The effects of pH and Mg2+ on the conformation and activity of chloroplast fructose 1,6-diphosphatase are discussed.
D002736:Chloroplasts / Q000201:enzymology*; D004229:Dithiothreitol / Q000494:pharmacology; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010944:Plants; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence
D006597:Fructose-Bisphosphatase; D008274:Magnesium; D004229:Dithiothreitol