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Selectivity and Regulation in the Phospholipase A 2 ‐Mediated Attack on Cholinergic Synaptic Vesicles by β‐Bungarotoxin
Author(s) -
Noremberg Krystyna,
Parsons Stanley M.
Publication year - 1986
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.1471-4159.1986.tb00756.x
Subject(s) - vesicle , synaptic vesicle , biochemistry , phosphatidylcholine , bungarotoxin , torpedo , chemistry , phospholipase a2 , fatty acid , phospholipase , enzyme , biophysics , biology , membrane , acetylcholine receptor , phospholipid , receptor
The total fatty acid composition of purified Torpedo californica electric organ synaptic vesicles was determined by GLC analysis of methyl esters. Limit amounts of fatty acids released by high concentrations of either β‐bungarotoxin (β‐BuTx) or Naja naja venom phospholipase A 2 (PLA 2 ) acting in deoxycholate are reported. The time and enzyme concentration dependence for β‐BuTx‐ and PLA 2 ‐induced release of fatty acids from intact synaptic vesicles indicate that PLA 2 is 100‐ to 1,000‐fold more active. The Ca 2+ dependence for β‐BuTx‐induced release of fatty acids also was determined. ATP inhibits β‐BuTx‐ but not PLA 2 ‐induced release of fatty acids from vesicles in a manner that can not be ascribed only to chelation of the required Ca 2+ . ATP, other nucleotides, and adenosine have complex effects on β‐BuTx‐induced release of fatty acids from egg yolk phosphatidylcholine dispersed in deoxycholate. The results suggest that β‐BuTx‐mediated hydrolysis of the cholinergic synaptic vesicle membrane is ∼10‐ to 100‐fold more effective at causing uncoupling of vesicles than is PLA 2 and that the enzymatic activity of β‐BuTx is subject to regulation by nucleotide‐like factors.