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MOBILIZATION OF SYNAPTIC MEMBRANE‐BOUND CALCIUM BY ACIDIC AMINO ACIDS 1
Author(s) -
Tan A. T.
Publication year - 1975
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.1471-4159.1975.tb07638.x
Subject(s) - glutamic acid , aspartic acid , amino acid , glycine , chemistry , cysteic acid , calcium , biochemistry , glutamine , synaptosome , chelation , membrane , cysteine , organic chemistry , enzyme , cystine
— A fluorescent chelate probe (chlorotetracycline) and radioactive 45 Ca were used to study the effects of amino acids on the calcium bound to external synaptosomal membranes isolated from guineapig brain. Acidic amino acids released some of the membrane‐bound calcium. On the basis of 45 Ca studies, the order of mobilization potency‐DL‐homocysteic acid and l ‐cysteic acid > l ‐aspartic acid, l ‐glutamic acid, d ‐glutamic acid > N ‐methyl‐ dl ‐glutamic acid and dl ‐cyteic acid‐is in general agreement with that found by fluorescent chelate method with the exception of N ‐methyl‐ dl ‐aspartic acid and N ‐methyl‐ dl ‐glutamic acid, which are at least as potent as dl ‐homocysteic acid. This order of potency is observed only with a fraction enriched in external synaptosomal membranes, but not with microsomes, myelin and mitochondria. Neutral and basic amino acids, including glutamine. glycine and γ‐aminobutyric acid are ineffective. These results suggest that acidic amino acids have a specific ability to mobilize membranebound calcium; this is consistent with the proposed role of some of these compounds as excitatory transmitters in the central nervous system.