Catalyzes the hydrolysis of nucleoside triphosphates and diphosphates in a calcium- or magnesium-dependent manner. Preferentially hydrolyzes nucleoside 5'-triphosphates, with substrate preference for UTP > GTP > CTP. Hydrolyzes ATP and nucleoside diphosphates only to a minor extent.
Cytoplasmic vesicle membrane ; Multi-pass membrane protein .