Catalysis of the dephosphorylation of an ATP-molybdate complex by calcium and magnesium ions.

Calcium and magnesium catalyze the dephosphorylation of a molybdate complex of adenosine triphosphate but not the corresponding molybdate complex of adenosine disphosphate. We conclude that catalysis of breaking the bond between the beta and gamma phosphates involves metal chelation of the alpha and beta phosphates. ATP hydrolysis with calcium was stimulated by phosphate, apparently because of formation of a calcium-phosphomolybdate complex. The reaction with magnesium, which does not form a comparable complex, was not affected by phosphate. Strontium, cadmium, and barium behaved like calcium. The reactions with transition metal cations showed autoinhibition.