If you own a cat, you have undoubtedly noticed your cat’s strong attraction to tuna. Scientists wanted to know what made this food so appealing because cats have a completely different sense of taste than humans. For example, their sweet taste receptor gene is disrupted and they have fewer bitter taste receptors than we do.
In their study published in the journal Chemical Sense, the researchers discovered that cats, like humans, use taste receptors that detect umami (also called monosodium glutamate) – this is a fifth base taste that translates to “tasty”, just like sweet, sour, bitter and salty.
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But unlike human umami receptors, cats’ umami receptors bind to two chemicals that are found in particularly high concentrations in tuna, making this fish all the juicier for our furballs.
Different mechanisms than in humans
For their study, the researchers showed for the first time that cats express the umami-related Tas1r1 gene in their taste buds. This, in conjunction with the Tas1r3 gene, enables the detection of umami. Scientists already knew that cats have TAs1r3 activity, but were unsure about Tas1r1.
But in cats, “the binding sites for glutamic and aspartic acid—the two amino acids most responsible for the human umami experience—have mutated, we learn. Unlike in humans, amino acids do not bind exclusively to the cat’s umami receptor. Instead, nucleotides found in meat and yeast bind to the cat’s receptor, and amino acids such as glutamic and aspartic acid can then have an amplifying effect – on the cat’s umami receptor. “The opposite of what happens in humans.”
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Since tuna contains the nucleotide inosine monophosphate and large amounts of the amino acid L-histidine, both powerful umami activators, this explains why this fish is so popular with cats. “The L-histidine content of tuna is much higher than that of other fish species and meat sources,” confirmed lead study author Scott McGrane.
These results were tested on a group of 25 cats. The team placed a series of bowls of water containing varying amounts of amino acids and nucleotides as well as control water in front of the cats.
These showed a strong preference for combinations that most strongly activated their umami receptors, “suggesting that taste is a key factor in cats’ food intake,” the study authors conclude.
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