Cats are peculiar in many things. Eating preferences are no exception: while practically all other mammals are crazy about sugar or other sweets, cats are not at all interested in sweets. Other flavors - bitter, sour, salty and "umami", the reaction to certain amino acids - are similarly pronounced in cats as in humans or dogs.

Scientists have therefore long suspected that cats can only perceive sweet things to a very limited extent or not at all.

To test this hypothesis, a team led by Joseph Brand from the Monell Chemical Senses Center in Philadelphia examined the taste receptor genes of domestic cats, tigers and cheetahs. In most mammals, the recognition protein for sweets consists of two interlocking proteins called T1R2 and T1R3.

Since T1R3 is also part of the umami receptor, which works perfectly in cats, the scientists focused their investigation on the T1R2 gene.

The evaluation showed that an important region of the gene is actually missing in the cat's genetic makeup. As a result of this change, the genome became inoperable, so that its information can no longer be translated into a protein.

The result is an inoperable receptor in the taste buds of the cat's tongue, write Brand and his colleagues in the journal "PLoS Genetics" (vol. 1, p. E3). Since this change affects not only domestic cats, but also wild cat species such as tigers and cheetahs, it probably developed relatively early in the evolution of cats.

Taste receptors can not only reflect the food preferences of a species, but can also be directly influenced by the choice of food in the course of evolution, the researchers write. However, what is cause and what is effect is difficult to understand.

Next, the scientists want to investigate whether the cats have become pure carnivores because of their changed taste buds or whether the constant protein-rich and low-carbohydrate food has changed the receptors.

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