Effects of Vanadate on the Plasma Membrane ATPase of Red Beet and Corn

Publisher Website
Google Scholar
Abstract
The effects of vanadate on the plant plasma membrane ATPase were investigated in plasma membrane fractions derived from corn roots and red beets. The Ki for vanadate inhibition of the plasma membrane ATPase from corn roots and red beets was between 6-15 .mu.M vanadate. In both membrane fractions, 80% to 90% of the total ATPase was inhibited at vanadate concentrations < 100 .mu.M. Vanadate inhibition was optimal at pH 6.5, enhanced by the presence of K+, and was partially reversed by 1 mM EDTA. The Mg:ATP kinetics for the plasma membrane ATPase were hyperbolic in both the absence and presence of vanadate. Vanadate decreased both the Km and Vmax of the red beet plasma membrane ATPase, indicating that vanadate inhibits the ATPase uncompetitively. These results indicate many similarities with respect to vanadate inhibition between the plant plasma membrane ATPase and other major ion-translocating ATPases from fungal and animal cells. The high sensitivity to vanadate reported here, however, differs from other reports of vanadate inhibition of the plant plasma membrane ATPase from corn, beets and in some instances oats.