High-affinity Ca2+-stimulated and Mg2+-dependent ATPase from rat osteosarcoma plasma membranes.
Transplantable rat osteosarcoma plasma membrane preparations contain high-affinity and low-affinity calcium-stimulated ATPases. The high-affinity enzyme displayed a K0.5 for calcium of 0.03 microM, a Vmax of 99.2 nmol/min/mg, and a requirement for magnesium ions. It was not inhibited by 20 microM trifluoperazine nor stimulated by the addition of 2 ng of calmodulin. Lack of stimulation with exogenous calmodulin may be related to the high endogenous calmodulin content of the membrane preparations. The low-affinity Ca2+- or Mg2+-ATPase displayed a K0.5 for calcium of approximately 2.40 mM (Vmax of 185 nmol/min/mg) and a K0.5 for magnesium of approximately 2.75 mM (Vmax of 250 nmol/min/mg).
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D012516:Osteosarcoma / Q000201:enzymology*; D051381:Rats; D011912:Rats, Inbred ACI; D014268:Trifluoperazine / Q000494:pharmacology
D002147:Calmodulin; D014268:Trifluoperazine; D004533:Egtazic Acid; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases