Effect of plictran on beef heart mitochondrial ATPases

The in vitro effects of plictran on oligomycin-sensitive Mg2+-ATPase and Ca2+-ATPase activities in beef heart mitochondria were studied. Beef heart mitochondrial fractions were prepared by the conventional centrifugation method. ATPase activities were measured by determining the inorganic phosphate released by the hydrolysis of ATP. Plictran inhibited both oligomycin-sensitive (o.s.) Mg2+-ATPase and Ca2+ ATPase activities at nanomolar concentrations. However, plictran did not affect the oligomycin-insensitive (o.i.) Mg2+-ATPase activity at any concentration studied. Substrate activation kinetics revealed that plictran inhibited o.s. Mg2+-ATPase uncompetitively and Ca2+-ATPase non-competitively. These results clearly indicate that plictran affects ATP synthesis and calcium ion transport in beef heart mitochondria.