title: Activation of Mg-ATPase (spectrin-dependent ATPase) by Ca2+.
abstract: The dependence of saponin-stimulated Mg-ATPase activity in the erythrocyte membrane on Ca2+ concentration was studied. In the membrane of freshly sampled human erythrocytes we found for this enzyme and Ca2+ an apparent dissociation constant of 0.611  mumol/l (SE +/- 0.106 mumol/l) and Hill coefficient of 0.93 (SE +/- 0.05). The enzyme is in most probability identical with Ca,Mg-ATPase of high affinity to Ca2+ described also as spectrin-dependent Ca,Mg-ATPase.
mesh_terms: D000251:Adenosine Triphosphatases / Q000097:blood*; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D012503:Saponins / Q000378:metabolism; D013049:Spectrin / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D012503:Saponins; D013049:Spectrin; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium