A Ca2+ -stimulated, Mg2+ -dependent ATPase activity in subcellular fractions from Schistosoma mansoni

A Ca2+-stimulated, Mg2+-dependent ATPase activity was found in subcellular fractions from Schistosoma mansoni. Its specific and relative activities were higher in the heterogeneous cuticle fraction and in the microsomal fraction. The K0.5 for ATPase activation by free Ca2+ was 0.2–0.5 μM. This is the first description of an ATPase activity stimulated by Ca2+ in the micromolar range in S. mansoni.