INHIBITION OF MAIZE ROOT H+-ATPASE BY FLUORIDE AND FLUOROALUMINATE COMPLEXES

Vesicles derived from maize roots retain a membrane-bound H+-ATPase that is able to pump H+ at the expense of ATP hydrolysis. The H+ pumping and the ATPase activity of these vesicles are inhibited by lithium fluoride and by the complex formed between fluoride and aluminum. The inhibition promoted by lithium fluoride increases as the MgCl2 concentration in the medium is increased from 2 to 20 mM. The inhibitory activity of both lithium fluoride and aluminum fluoride increases as the temperature of the medium is increased from 20 to 35 degrees C. Inorganic phosphate (10-40 mM) inhibits the H+-ATPase at pH 6.5 but not at pH 7.0, and at both pH values, it antagonizes the inhibition promoted by lithium fluoride and fluoroaluminate complexes.