American scientists, have recognised an amino-acid taste receptor.Dr Charles S. Zuker, from the Howard Hughes Medical Institute and the University of California, San Diego, reports his team's findings in a recent journal. Humans can identify five different tastes — bitter, salty, sour, sweet, and umami. Umami is the flavour associated with monosodium glutamate (MSG).Receptors that responded to umami have been discovered by Japanese researchers ten years ago.
In opposition to popular understanding, taste is not experienced on different parts of the tongue. There are small differences in sensation, which can be cadenced with highly specific instruments, but all taste buds can respond to all types of taste, said Professor Laing.The US researchers are working on the premise that taste is based on different combinations of receptors, though the exact receptor mechanisms are still being sorted out.They have focused on T1R receptors, a family of proteins remotely related to receptors in the brain that recognise the amino acid glutamate and related chemicals.Different T1R genes can be expressed in cells in different combinations to yield cells that respond to a specific taste. For example, T1R2 and T1R3 joined together function as a sweet receptor.
The researchers have found that combining T1R1 and T1R3 creates a response for amino acids.Taste research is a hot field at the moment, said Professor Laing. Recent advances in molecular biology have allowed researchers to work with larger amounts of cloned receptors, rather than with the small numbers available in the tongue.The lumps on the tongue that are often called 'taste buds' are actually papillae. These have several pores in them, which are the ends of taste buds that contain active cells. When a flavour is in the mouth it moves down the pores and spurs the taste cells.Taste receptors have now been identified for amino acids, bitter, and sweet tastes. The US researchers hope this will allow them to map the system so they can understand how taste is encoded.
