Domestic cats (Felis silvestris catus) and their wild relatives from the family Felidae are obligate carnivores. They do not show preferences for sweeteners, but otherwise have the normal sense of taste.[64,65,69] We have identified the cat Tas1r2 and Tas1r3 genes.[56] The cat Tas1r3 gene shows high sequence similarity with functional Tas1r3 genes of other species and is expressed in taste buds. However, the cat Tas1r2 is a pseudogene (Figure 1) with no evidence of its expression. The Tas1r2 genes of three other Felidae species, the tiger (Panthera tigris), cheetah (Acinonyx jubatus) and Asiatic lion (Panthera leo persica), are also pseudogenes.[56,69] Because cat Tas1r2 is an unexpressed pseudogene, a functional sweet taste receptor heteromer T1R2+3 cannot form, which explains the molecular origins of sweet taste blindness in cats.
