Senomyx Inc. announced that the company's scientists have discovered that the human sweet taste receptor contains multiple binding sites for sweeteners and sweet taste inhibitors. A binding site for such sweet taste modulators was also identified in the related umami receptor, which mediates the savory taste of monosodium glutamate, or MSG. The company also announced that these results have been published in a manuscript authored by Senomyx employees Xu et al. and appeared online in the September 7 early edition of the Proceedings of the National Academy of Sciences. The manuscript by Xu et al. can be viewed at http://www.pnas.org/cgi/content/abstract/0404384101v1.

These discoveries, made by Senomyx senior scientists Xiaodong Li, Ph.D., Hong Xu, Ph.D. and coworkers, identify multiple binding sites on the human sweet taste receptor, a protein complex composed of T1R2 and T1R3 G protein-coupled receptors (GPCRs). Using cells engineered to express receptor chimeras, Li's team showed that sweeteners such as aspartame interact with the extracellular domain of T1R2. In contrast, sweeteners such as cyclamate and the sweet taste inhibitor lactisole interact with the transmembrane domain of T1R3. Additional studies described in the publication demonstrated that cyclamate and lactisole also interact with T1R3 of the umami, or savory, receptor, which is composed of T1R1 and T1R3.