Figure 4.

Taste receptor mechanisms for the 5 basic tastes. A) Sweeteners and sugars stimulate the sweet taste receptor, T1R2/3, and activate downstream pathways. It has been suggested that sugars activate a phospholipase C–dependent pathway, while artificial sweeteners activate an adenylyl cyclase (AC) pathway. B) Monosodium glutamate activates the umami receptor, T1R1/3, and subsequently a phospholipase C pathway. C) Bitter signal transduction is mediated by 25 T2R receptors. Like the sweet receptors, bitter receptors are thought to activate both phospholipase C and AC pathways. D) Evidence suggests that a potassium channel maybe responsible for mediating or enhancing bitter tastes. E) Sour taste is thought to be mediated by PKD and ASIC channels, which are distributed on different populations of papillae. F) Salt taste is mediated by an amiloride-sensitive ENAC channel in rodents, but humans appeared to downregulated ENAC and have a less sensitive amiloride-insensitive system that has yet to be identified.