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Detergent Effects on the Phosphatidylinositol‐Specific Phospholipase C in Rat Brain Synaptosomes
Author(s) -
Manning Robert,
Sun Grace Y.
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb00887.x
Subject(s) - egta , chemistry , phosphatidylinositol , divalent , phospholipase c , biochemistry , membrane , hydrolysis , phospholipase , substrate (aquarium) , calcium , synaptosome , chromatography , enzyme , biology , signal transduction , ecology , organic chemistry
In the presence of Ca 2 + (2.5 m M ) and using [ 14 C]arachidonoyl phosphatidylinositol (PI) membrane as substrate, phosphatidylinositol‐specific phospholipase C (PI‐PLC) (EC 3.1.4.10) in rat brain synaptosomes was activated by deoxycholate but not taurocholate. Calcium stimulated enzymic hydrolysis by both detergents, but the stimulatory effect of taurocholate was less than that of deoxycholate. Peak stimulation for deoxycholate was observed at 1 mg/ml, whereas that for taurocholate was 4 mg/ml. When 1 m M EDTA was added to the taurocholate (4 mg/ml) and Ca 2 + (3.5 m M ) system, synaptosomal PI‐PLC activity was greatly stimulated, to almost the same level as the deoxycholate + Ca 2 + system. This system required the presence of all three factors, and EGTA could not effectively replace EDTA in the stimulatory action. The detergent‐induced hydrolysis of synaptosomal PI by the deoxycholate + Ca 2 + and the taurocholate + Ca 2 + + EDTA systems was strongly inhibited by divalent metal ions such as Zn 2 + , Cu 2 + , Pb 2 + , and Fe 2+ , whereas Mg 2 + and Ca 2+ were ineffective. Nevertheless, only the deoxycholate + Ca 2 + system was responsive to enzyme inhibition by membrane‐perturbing agents such as lysophospholipids and free fatty acids. The specific requirement for EDTA in the taurocholate system may be due to the release of a pool of inhibitory divalent metal ions from the membranes.