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The Taste of Carbonation

Science  16 Oct 2009:
Vol. 326, Issue 5951, pp. 443-445
DOI: 10.1126/science.1174601

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Gee Fizz

The next time you enjoy a carbonated beverage, you can do so with an enhanced understanding of the molecular mechanism that provides its distinctive flavor sensation. Chandrashekar et al. (p. 443) genetically ablated specific sets of taste cells in mice and found that the sensation of CO2 was lost in animals lacking taste cells that sense sour flavors. A screen for genes specifically expressed in these cells revealed the gene encoding carbonic anhydrase 4, which catalyzes hydration of CO2 to form bicarbonate and free protons. Knockout animals not expressing the carbonic anhydrase 4 gene also showed diminished sensation of CO2. The protons produced by the enzyme appear to be the actual molecules sensed by the sour-sensitive cells. This process, combined with tactile sensations, appears to be the source of the popular fizzy sensation.

Abstract

Carbonated beverages are commonly available and immensely popular, but little is known about the cellular and molecular mechanisms underlying the perception of carbonation in the mouth. In mammals, carbonation elicits both somatosensory and chemosensory responses, including activation of taste neurons. We have identified the cellular and molecular substrates for the taste of carbonation. By targeted genetic ablation and the silencing of synapses in defined populations of taste receptor cells, we demonstrated that the sour-sensing cells act as the taste sensors for carbonation, and showed that carbonic anhydrase 4, a glycosylphosphatidylinositol-anchored enzyme, functions as the principal CO2 taste sensor. Together, these studies reveal the basis of the taste of carbonation as well as the contribution of taste cells in the orosensory response to CO2.

  • To whom correspondence should be addressed. E-mail: cz2195{at}columbia.edu

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