Evidence that both Ca 2+-ATPase and (Ca 2+ + Mg 2+)-ATPase activities in the plasma membrane-rich fraction from bovine parotid gland reside on the same enzyme molecule

Abstract

1. 1. Evidence was obtained that activities of both low-affinity Ca 2+-ATPase and high-affinity (Ca 2+ + Mg 2+)-ATPase in the plasma membrane-rich fraction from bovine parotid gland reside on the same enzyme. 2. 2. Two solubilized ATPases were purified by four steps of HPLC; and both activities eluted at the same fractions from each column, and the specific activity ratio of the two enzymes at each step was constant. 3. 3. By non-denaturing PAGE, the final preparation gave a single band for both protein staining and activity staining for the two ATPases; and the Ca 2+-ATPase activity comigrated with that of (Ca 2+ + Mg 2+)-ATPase. 4. 4. In SDS-PAGE, each activity staining for the ATPases also gave a single band, and both activities comigrated. 5. 5. These findings suggest that Ca 2+-ATPase and (Ca 2+ + Mg 2+)-ATPase are a single enzyme.