Taste, Chemical Biology of

The mammalian sense of taste is crucial for evaluating food palatability and nutritional quality. To achieve the detection of relevant chemicals, evolution has shaped a set of receptor molecules that allow the detection of five basic taste qualities: sweet, umami, bitter, salty, and sour. Each taste modality has unique characteristics and serves a distinct function for an animal's nutrition. Therefore, we address the characteristics, the recent advances, the persisting difficulties, and the future perspectives of the basic taste qualities in separate paragraphs. Enormous progress has been made in the identification and the characterization of taste receptor molecules, and in the growing number of animal genomes accessible from databases, which has inspired us to devote a section of this review to discuss a series of sophisticated evolutionary studies on taste receptor molecules. Finally, evidence is accumulating to show that taste receptor and signal transduction molecules have nongustatory functions as well. The extragustatory expression of such genes and the resulting implications are summarized in the final section.