Binding of Amino Acids to a Membrane Fraction of Taste Epithelia in Carp.

Abstract

The amino acid binding properties of membrane fractions prepared from carp taste epithelia were compared to the results with those obtained in electrophysiological experiments. Electrophysiological cross-adaptation experiments using 12 amino acids showed that receptive mechanisms for these chemicals were able to be classified into six categories. The amount of binding of each amino acid was dose-dependent. Ligand bindings were also specific for membrane fractions of the taste epithelia, because the binding to those from carp head skin without taste buds was negligible. The binding of each amino acid indicates the existence of specific taste receptor binding sites in the facial taste system of the carp. However, there were some cases in which ligands competitively inhibited the binding of the parent amino acids, e. g., L-cysteine affected the binding of almost all the amino acid tested. Although this binding experiment itself could not totally explain the specificity of amino acid responses with electrophysiology, this specificity of response properties from this study could indicate that each ligand binds to specific receptor sites on the taste cell membrane.