Fluoride effects on the plasma membrane ATPase of sugarbeet

Fluoride, a common air pollutant long known as a toxicant to many plant processes, inhibits mitochondrial, chloroplast and tonoplast ATPases. In the present study, the effects of fluoride at various substrate concentrations on the plasma membrane ATPase of sugarbeets (Beta vulgaris L.) were investigated. The plasma membrane ATPase was inhibited by lower concentrations (5 mM) of fluoride than the above indicated ATPases. The amount of inhibition due to fluoride increased with increasing concentrations of free Mg²⁺ in the reaction medium. The data suggest that fluoride inhibition of the plasma membrane ATPase is at the active site of the enzyme and occurs via a magnesium-fluoro-complex.