BINDING OF UMAMI SUBSTANCE TO PLASMA-MEMBRANE ISOLATED FROM BOVINE CIRCUMVALLATE PAPILLAE

Fractionation of several kinds of membranes from the taste organ, circumvallate papillae, of bovine has been done to investigate localization of the umami substance binding site. Monosodium glutamate (MSG) and nucleotides are known as umami substances. The membrane fractions obtained from a series of centrifugation were examined for radioactive MSG binding activities by the ligand-binding methods, indicating a synergistic effect between MSG and nucleotides. They were also measured for activities of the marker enzymes. The membrane fraction that seemed to be rich in plasma membrane, on the basis of the marker enzyme activities, had specific MSG binding activity. These results suggest that umami substances bound to the plasma membrane of circumvallate papillae.