title: Phospholipid requirement of Ca2+-stimulated, Mg2+-dependent ATP hydrolysis in rat brain synaptic membranes.
abstract: The phospholipid requirement for Ca2+-stimulated, Mg2+-dependent ATP hydrolysis (Ca2+/Mg2+-ATPase) and Mg2+-stimulated ATP hydrolysis (Mg2+-ATPase) in rat brain synaptosomal membranes was studied employing partial delipidation of the membranes with phospholipase A2 (Hog pancreas), phospholipase C (Bacillus cereus) and phospholipase D (cabbage). Treatment with phospholipase A2 caused an increase in the activities of both Ca2+/Mg2+-ATPase and Mg2+-ATPase whereas with phospholipase C treatment both the enzyme activities were inhibited. Phospholipase D treatment had no effect on Ca2+/Mg2+-ATPase but Mg2+-ATPase activity was inhibited. Inhibition of Mg2+-ATPase activity after phospholipase C treatment was relieved with the addition of phosphatidylinositol-4,5-bisphosphate (PIP2) and to a lesser extent with phosphatidylinositol-4-phosphate (PIP) and phosphatidylcholine (PC). Phosphatidylserine (PS), phosphatidic acid (PA), PIP and PIP2 brought about the reactivation of Ca2+/Mg2+-ATPase. Phosphatidylinositol (PI) and PA inhibited Mg2+-ATPase activity. Kms for Ca2+ (0.47 microM) and Mg2+ (60 microM) of the enzyme were found to be unaffected after treatment with the phospholipases.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010740:Phospholipases / Q000378:metabolism; D010743:Phospholipids / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013570:Synaptic Membranes / Q000201:enzymology*; D013574:Synaptosomes / Q000201:enzymology
chemical_list: D010743:Phospholipids; D010740:Phospholipases; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases