[Allosteric properties of CF1-ATPase form chloroplasts]

The inhibiting effect of ADP and Mg2+ on CF1-ATPase from chloroplasts depending on their concentration, pH and the presence of stimulating agents of various origin was studied. It was shown that the low Mg-dependent activity of the soluble enzyme is due to non-competitive inhibition of the reaction by Mg2+ in the presence of ADP. The CF1-ATPase stimulators lower the inhibiting effect, thus allowing to detect the "true" Mg-dependent activity of the enzyme. The data obtained are indicative of the existence of Mg2+- and ADP-specific sitein the enzyme, which controls its catalytic activity. The properties and possible role of this site in photophosphorylation are discussed.