Sweetness and bitterness are key determinants of food acceptance and rejection respectively Sugars such as sucrose and fructose are generally recognized as sweet However not all sugars are sweet and even anomers may have quite different tastes For example gentiobiose is bitter whereas its anomer isomaltose is sweet Despite this unique sensory character the molecular basis of the bitterness of gentiobiose remains to be clarified In this study we used calcium imaging analysis of human embryonic kidney 293T cells that heterologously expressed human taste receptors to demonstrate that gentiobiose activated hTAS2R16 a bitter taste receptor but not hT1R2/hT1R3 a sweet taste receptor In contrast isomaltose activated hT1R2/hT1R3 As a result these anomers elicit different taste sensations Mutational analysis of hTAS2R16 also indicated that gentiobiose and beta-D-glucopyranosides such as salicin share a common binding site of hTAS2R16 (C) 2010 Elsevier Inc All rights reserved