An enzyme that catalyzes the hydrolysis of ATP and is activated by millimolar concentrations of either Ca(2+) or Mg(2+). Unlike CA(2+)-TRANSPORTING ATPASE it does not require the second divalent cation for its activity, and is not sensitive to orthovanadate. (Prog Biophys Mol Biol 1988;52(1):1). A subgroup of EC 3.6.1.3.