Substrate-specificity of “high-affinity”, Na +-independent binding of β-alanine to cerebral synaptosomal-mitochondrial fractions

Abstract

1. The substrate-specificity and the effects of some drugs on the “high-affinity”, Na +-independent binding of β-alanine (5.4 × 10 −9 M) were examined in freshly-prepared and frozen/thawed synaptosome-enriched fractions of rat brain. 2. “Specific” β-alanine binding occurred to a greater extent to freshly-prepared fractions (5.13 p-moles/g) than to frozen/thawed fractions (2.88 p-moles/g). 3. β-Alanine binding was potently inhibited by glycine, α-alanine, serine, valine, leucine, α-aminobutyric acid and β-aminoisobutyric acid, but was not affected by taurine or GABA. 4. β-Alanine binding was reduced by both strychnine and bicuculline. 5. This β-alanine-receptor might be identical to the synaptic glycine-receptor. but it differs from the synaptic GABA-receptor, the synaptic taurine-receptor, strychnine-receptors, and from “high-affinity” transport-receptors for glycine and β-alanine.