Research on the mechanism behind the reception of taste substances [1], [2] has a short history; Taste-2 receptors (T2Rs), bitterness receptors present in taste cells, were discovered in 2000 [3]–[5] followed by the discovery of sweetness receptors (T1R2+T1R3) [6] and umami receptors (T1R1+T1R3) [7].