A plasma membrane Mg2+-ATPase in the cellular slime mold Dictyostelium discoideum.

Evidence is presented for the existence of a plasma membrane ATPase in Dictyostelium discoideum. The enzyme is dependent on Mg+2, and is insensitive to both azide and oligomycin. It is, however, sensitive to diethylstilbestrol, dicyclohexylcarbodiimide, vanadate, and thimerosal. Monovalent cations (Na+, K+, and choline) have no effect on enzyme activity, but high concentrations of Ca+2 are highly inhibitory. Vegetative cells express the highest amount of enzyme activity; the activity decreases three- to fourfold during the early stages of differentiation, and then remains constant during the latter stages.