Umami taste receptor
Li, Xiaodong Senomyx, Incorporated, San Diego, California.
Last reviewed:July 2020
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- Perception of taste
- Experimental findings and modeling
- GPCR modulators
- Related Primary Literature
- Additional Reading
A type of cell receptor in taste buds that detects the savory taste quality known as umami. Umami is one of the five basic taste qualities that humans can detect, along with sweet, bitter, salty, and sour. It was discovered in 1908 by Kikunae Ikeda, a professor of chemistry at Tokyo Imperial University, while doing research on the strong flavor in seaweed broth. However, it took many years until umami was accepted as a basic taste. Umami in Japanese means roughly "delicious." It is often used to describe the "meaty" or "savory" flavor common to a variety of food products, such as seafood, meat, cheese, and mushrooms. The primary umami tastant (any chemical that stimulates the sensory cells in a taste bud; Fig. 1) is L-glutamate, which is a naturally occurring amino acid found in abundance in protein-rich foods. A secondary umami tastant is aspartate (an amino acid structurally similar to L-glutamate). The most unique characteristic of umami taste is the synergy between glutamate and purinic ribonucleotides [for example, inosine 5′-monophosphate (IMP)]. IMP is an enhancer of umami taste; that is, it does not taste as umami at submillimolar concentration, but can strongly potentiate the umami taste of glutamate. Progress in the molecular biology of the umami taste receptor has revealed the molecular mechanism of the synergy between the two umami ligands (that is, molecules with an affinity to bind to the umami receptor). This novel mechanism provides insights into allosteric modulation (in which modulators bind to regulatory sites distinct from the active site on the enzyme or protein, resulting in conformational changes that may profoundly influence enzyme or protein function) of G protein–coupled receptors (GPCRs). [G proteins are guanosine 5′-triphosphate (GTP)–binding proteins. The GPCRs are cell-surface receptors that, when activated by the binding of a ligand, in turn activate a cytosolic G protein molecule, initiating a cascade of reactions effecting the intracellular response to the extracellular signal (the ligand).] See also: Amino acid; Chemical senses; Ligand; Monosodium glutamate; Protein; Sensation; Sense organ; Spice and flavoring; Taste
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