Genetic studies conclude that cats cannot sense “sweetness”. Not only cat actually, but also most of its family such as tiger, lion, and cheetah. They are unable to recognize sweet taste; although “attractive” and “tasting” ability are used for mammals to detect calories.
Researchers looked into the genetic of cat family and found that they lack the 247 pairs of genetics called Tas1r2 gene, which encodes T1R2, one of two protein subunits that make the sweet taste receptor in most mammals. Scientists prejudiced that the protein was functioning in the common ancestor of the cat, but not anymore. Meanwhile, the partner subunit, namely T1R3, can function well.
Mammalian sweet-taste receptor is formed by the dimerization of two proteins (T1R2 and T1R3; gene symbols Tas1r2 and Tas1r3), scientist identified and sequenced both genes in the cat. The cat Tas1r3 gene shows high sequence similarity with functional Tas1r3 genes of other species. In situ hybridization and immunohistochemical studies demonstrate that Tas1r3 is expressed, as expected, in taste buds. However, the cat Tas1r2 gene shows a 247-base pair microdeletion in exon 3 and stop codons in exons 4 and 6. There was no evidence of detectable mRNA from catTas1r2, and no evidence of protein expression by immunohistochemistry. Tas1r2 in tiger and cheetah and in six healthy adult domestic cats all show the similar deletion and stop codons. Scientist conclude that cat Tas1r3 is an apparently functional and expressed receptor but that cat Tas1r2 is an unexpressed pseudogene. A functional sweet-taste receptor heteromer cannot form, and thus the cat lacks the receptor likely necessary for detection of sweet stimuli. This molecular change was very likely an important event in the evolution of the cat’s carnivorous behavior.
Scientist then questioned:
“the cat become carnivores because they are can not recognizing a sweet taste, or otherwise they are disable the gene identifiers to taste sweet because they are carnivores?”
If we call our cat “sweety”; do they understand what is it mean? I think it’s no longer a good compliment that will interests them.
However, out of the taste sense, they are always look “sweet” for me, especially when they are smile
Access to the full text (PDF) journal: Waltham International Nutritional Sciences Symposia