PLANT PHYSIOLOGY , Vol 108, Issue 1 241-246, Copyright © 1995 by American Society of Plant Biologists
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BIOCHEMISTRY AND ENZYMOLOGY |
Inhibition of Maize Root H+-ATPase by Fluoride and Fluoroaluminate Complexes
A. R. Facanha and L. de Meis
Instituto de Ciencias Biomedicas, Departamento de Bioquimica, Universidade Federal do Rio de Janeiro, Cidade Universitaria, Ilha do Fundao, RJ 21941-590, Brazil
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[deg]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.