title: (Ca-2+ + Mg-2+)-Activated ATPase in the plasma membrane mouse liver cells.
abstract: 1. Purified plasma membranes from dissociated adult mouse liver cells posses a (Ca-2+ + Mg-2+)-stimulated ATPase (EC 3.6.1.3) activity. 2. Enzyme activity is at a maximum with the addition of 0.3 mM Ca-2+ and 3 mM Mg-2+. 3. Using medium devoid of alkali metal ions (Ca-2+ + Mg-2+)-ATPase enzyme activity was observed with Km1 = 0.35 - 10-3 M at a substrate concentration of 1 mM or less and an apparent Km2 = 0.88 - 10-3 M at higher substrate concentrations. 4. In the presence of Na+ and 4 mM ATP, an increase in activity was seen, suggesting the presence of a (Ca-2+ + Mg-2+ + Na+)-activated ATPase. 5. In the presence of both Na+ and K+ the (Ca-2+ + Mg-2+)-dependent enzyme activity was further increased, indicating that a (Ca-2+ +Mg-2+ + K+)-stimulated ATPase may also be present.
mesh_terms: D000255:Adenosine Triphosphate; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology*; D051379:Mice; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
chemical_list: D000255:Adenosine Triphosphate; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium