The receptors for umami taste are specifically stimulated by:

Umami taste is due to activation of a truncated metabotropic receptor, mGluR4, in the taste buds. Glutamate in food may also activate ionotropic glutamate receptors to depolarize umami receptors. Sucrose stimulates sweet receptors; quinine activates receptors for bitter taste. Lysyl taurine is a compound that activates receptors for salty taste. Salt and sour tastes are triggered by activation of ionotropic receptors (ligand-gated ion channel) Sour, bitter, and umami tastes are triggered by activation of metabotropic receptors (GPCRs).