Isolated or biologically pure taste receptors comprised of at least one T1R1 and T1R3 polypeptide and compositions containing are provided. These taste receptors specifically bind to and/or are specifically activated by umami taste stimuli such as glutamate compounds. These taste receptors are useful in screening assays for identifying compounds that elicit or modulate (enhance or inhibit) umami taste. Such compounds can be used as additives and flavorants to improve the taste of compositions for human or animal consumption. In preferred embodiments, the T1R1/T1R3 receptor will be comprised of human T1R1/human T1R3 expressed in association with a suitable G protein, e.g. G.sub..alpha.15.