Lysophosphoinositide-specific phospholipase C in rat brain synaptic plasma membranes |
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Authors: | Tomonari Tsutsumi Tetsuyuki Kobayashi Hiroshi Ueda Emiko Yamauchi Shiro Watanabe Harumi Okuyama |
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Affiliation: | (1) Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabedori, Mizuhoku, 467 Nagoya, Japan;(2) Present address: Dept. of Biochem., Oita Medical University, Hasama-machi, 879-55 Oita, Japan |
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Abstract: | 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.Abbreviations PI phosphatidylinositol - lysoPI lysophosphatidylinositol - lysoPI-PLC lysophosphoinositide-specific phospholipase C - PI-PLC phosphoinositide-specific phospholipase C - MG monoacylglycerol - PLC phospholipase CTo whom to address reprint requests. |
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Keywords: | Phosphatidylinositol lysophosphatidylinositol phospholipase C synaptic plasma membranes subcellular distribution |
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