Lysophosphoinositide-specific phospholipase C in rat brain synaptic plasma membranes.
A membrane preparation from rat brain catalyzed the hydrolysis of [2-3H]glycerol-labeled lysophosphatidylinositol (lysoPI) to yield monoacylglycerol (MG) and inositolphosphates. This phospholipase C activity had an optimal pH of 8.2. The membrane preparation did not require the addition of Ca2+ for its maximum activity, but the activity was inhibited by addition of 0.1 mM EDTA to the assay mixture and was restored by simultaneous addition of 0.2 mM Ca2+. The activity was found to be localized in synaptic plasma membranes prepared by Ficoll and Percoll density gradients. The phospholipase C was highly specific for lysoPI; diacylglycerol formation from phosphatidylinositol, and MG formation from lysophosphatidylcholine, lysophosphatidylethanolamine, and lysophosphatidylserine were below 5% of that observed with lysoPI under the conditions used. We concluded that there is a pathway for phosphatidylinositol metabolism in brain synaptic membranes which is different from the well-characterized phosphoinositide-specific phospholipase C pathway.
Tsutsumi
T
T
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
Kobayashi
T
T
Ueda
H
H
Yamauchi
E
E
Watanabe
S
S
Okuyama
H
H
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D004492:Edetic Acid / Q000494:pharmacology; D005990:Glycerol; D007700:Kinetics; D008246:Lysophospholipids / Q000138:chemical synthesis / Q000378:metabolism*; D008297:Male; D051381:Rats; D013379:Substrate Specificity; D013570:Synaptic Membranes / Q000201:enzymology*; D014316:Tritium; D010738:Type C Phospholipases / Q000302:isolation & purification / Q000378:metabolism*
D008246:Lysophospholipids; C025449:lysophosphatidylinositol; D014316:Tritium; D004492:Edetic Acid; D010738:Type C Phospholipases; D005990:Glycerol