Notizen: A New Method to Prepare Membrane Fractions Containing Ionophore-Stimulated ATPase from Pumpkin Hypocotyls (Cucurbita maxima, L .)

Abstract In membrane fractions from pumpkin hypocotyls AT­Pase activity was stimulated by a combination of CCCP (carbonyl cyanide m-chlorophenylhydrazone), a protonophore, and valinomycin, a K+-ionophore. Singly, these ionophores stimulated ATPase activity much less. Nigericin, an H+/K+-antiporter, and nystatin, a cation pore, had similar effects as the combination of CCCP and valinomycin. The results suggest the presence of a cation-translocating ATPase which is stimulated by ionophores by dissipating cation gradients formed in the vesicles. A major part of the ionophore-stimulated ATPase activity correlated with marker enzymes for plasma membranes but part of it could be located in other compartments.