Sweet and umami TAS1R receptors: from molecular recognition to physiological function.

The detection of sweet and umami tastants is mediated by 2 heterodimeric G protein-coupled receptors, TAS1R2/TAS1R3 and TAS1R1/TAS1R3, respectively. Sweet taste provides input related to the carbohydrate-derived energy content of ingested food, whereas the physiological role of umami taste by detecting free L-amino acids is to signal the presence of protein-rich foods. In addition to being expressed in the oral cavity, TAS1R receptors are expressed in numerous extraoral tissues and organs, including the gut, where their physiological roles are not yet fully understood. In this review, we present an overview of the current knowledge on these taste receptors since their discovery in the early 2000s. We summarize the structure-function analyses, evolution, and expression of TAS1R genes and describe the molecular basis for the recognition of sweet and umami tastants. Together, these insights provide a comprehensive understanding of how TAS1R receptors contribute to nutrient detection and metabolic regulation both in taste perception and beyond.