Cartoon #200: “Cats Don’t Taste Sweets”

It looks like Garfield, the cartoon cat, will have to stick to lasagna from now on. In case he, or you, missed it, here is the synopsis of the article in the debut issue of the Public Library of Science online journal.

Although sweet sugars are ubiquitous in human foods, they are seldom added to cat food, and owners usually do not feed sweets to their cats.
This is because, in contrast to most other mammals, both domestic cats and their wild cousins, the big cats, do not show a preference for and, most likely, cannot detect sweet-tasting compounds. Other than this sweet blindness, the cat’s sense of taste is normal.

The molecular mechanism for this unique behavior towards sweets was not known, until now. Sweet compounds, including sugars and artificial sweeteners, are recognized by a special taste bud receptor composed of the products of two genes. The authors found that in cats, one of these genes is not functional and is not expressed. (It is called a pseudogene.)

Because the sweet receptor cannot be formed, the cat cannot taste sweet stimuli. During the evolution of the cats’ strictly carnivorous behavior, selection to maintain a functional receptor was apparently relaxed. This research provides a molecular explanation for the common observation that the cat lives in a different sensory world than the cat owner.

[Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar, Public Library of Science, Vol. 1, No. 1, July, 2005, citing Li X, Li W, Wang H, Cao J, Maehashi K, et al. (2005) Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar. PLoS Genet 1(1): e3]