Mg 2+ and Ca 2+ Activated ATPase Activities of Bovine Aortic Microsomes 1

Summary

Microsomes from bovine aorta contained a magnesium activated or “basic” ATPase activity and a calcium activated ATPase activity that was independent of magnesium. Ca²⁺ stimulated Mg²⁺ dependent “extra” ATPase was not demonstrable. Kinetic analyses of the magnesium basic ATPase and calcium ATPase activities suggested that the magnesium activation and calcium activation of ATP hydrolysis probably represent a single enzyme moiety. The ATPase has equal affinity for magnesium and calcium and does not distinguish between them.