taste buds taste receptor gene mutation sweetness acids amino acids TAS1R1 TAS1R3 umami glutamic acid aspartic acid amino acids nucleotides inosine monophosphate l-Histidine tuna palatability tuna
Cats have relatively few taste buds compared to humans (470 or so versus more than 9,000 on the human tongue). Domestic and wild cats share a taste receptor gene mutation that keeps their sweet taste buds from binding to sugary molecules, leaving them with no ability to taste sweetness. They, however, possess taste bud receptors specialized for acids, amino acids like protein, and bitter tastes. Their taste buds possess the two receptors TAS1R1 and TAS1R3 needed to detect umami. These receptors contain molecular changes that reduce their detection of glutamic acid and aspartic acid, the main amino acids tasted as umami flavor in humans while enhancing their detection of the nucleotides inosine monophosphate and free l-Histidine. These nucleotides are particularly enriched in tuna.. One of the researchers involved in this research has claimed, "I think umami is as important for cats as sweet is for humans". In their research paper they specifically argue the sensitivity to histidine and inosine explains the palatability of tuna for cats: "the specific combination of the high IMP and free l-Histidine contents of tuna, which produces a strong umami taste synergy that is highly preferred by cats".
