Defective Sweet Taste Receptor in Cats

Most mammals can taste bitter, sweet, salty, sour, and amino acids, such as glutamate (umami). The receptors for sweet and umami are paired G proteins, called T1Rs, that are expressed exclusively in the taste buds. T1R1 and T1R3 together respond to the umami taste. Similarly, T1R2 and T1R3 together recognize diverse natural and synthetic sweeteners. T1R2 and T1R3 are encoded by the genes Tas1r2 and Tas1r3. Cats, unlike puppies, do not prefer sweet foods. Previous work had demonstrated that alleles of Tas1r3 predict sugar intake. These investigators tested a simple hypothesis: cats are indifferent to sugar because their sweet taste genes are defective. Here, they show that the cat Tas1r2 gene has a large deletion in the coding region and no messenger RNA can be detected. They found similar deletions in the genes of tiger, cheetah and domestic cats and conclude that this is important in the evolution of the cat as carnivore.
Li et al. PLoS Genetics Volume 1 | Issue 1 | JULY 2005"