A taste for glutamate helped ape change their diet

Our taste sensations are composed of five basic tastes: bitter, salty, sweet, sour and umami, or protein, or, as it is also called, glutamate taste – because umami taste receptors are especially active in responding to the amino acid glutamate. It is believed that all other tastes are combinations of these five (although there are quite unexpected discoveries – for example, we once wrote that sour taste receptors are also responsible for a separate taste of water).

But our taste buds did not fall from the sky on us. If you look at other animals, you can find the same receptor proteins in them, only they will react to other substances. That is, taste buds in the course of evolution, passing from one species to another, mutated and changed their structure – and began to give a new taste.

The University of Tokyo and Kyoto University staff describe in Current Biology a rather curious evolutionary path that the T1R1 / T1R3 receptor, or the umami taste receptor, has taken. The fact is that not all animals have it that actively responds to glutamate. For example, in mice, the umami receptor is excited predominantly when free nucleotides appear. There are a lot of free nucleotides in insects, and the mouse in its natural habitat meets a lot.

However, the umami receptors in monkeys called the Bolivian saimiri have the same low sensitivity to glutamate. The researchers suggested that umami receptors changed specialization during the evolution of primates. To test this, they experimented with cells that synthesized receptors by the minds of seventeen primate species. In addition to the above-mentioned Bolivian saimiri, non-glutamate receptors by umami turned out to be in three other species: common marmosets, Filipino tarsiers and fat-tailed galago. All four eat a lot of insects, so it is clear that they would be better off having an “insectivorous” version of the receptor. If we talk about the “glutamate” version of the receptor, then the receptors of the gorilla and human minds react most strongly to glutamate. Additional experiments have shown that in the gene for the insectivorous variant of the receptor in the Bolivian Saymiri, it is enough to change only two nucleotides – two genetic letters – for the receptor to begin to react predominantly to glutamate.

Although the umami receptor has been linked to the taste of meat, the monkeys needed it not so much for the meat as for the fruits and leaves of plants. Compared to insects, fruits and leaves contain less free nucleotides and much more glutamate. That is, a mutation in the umami receptor helped the primates to stop being carried away by insects and to master plant food.

Among primates, there are those in which the umami receptor reacts equally to “insects” free nucleotides, and to glutamate – these are feline lemurs. But lemurs (and lorises) have a pretty good sense of smell, at least compared to other primates. So if ring lemurs find it difficult to decide by taste what they want more, their nose will help them with this.

Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.

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