The pleasure that everyone finds in drinking carbonated beverages – especially in the festive season! – is often attributed to mechanical agitation of the tongue caused by the bubbles. However, it is actually an effect caused by the carbon dioxide itself and researchers in the US have identified in the laboratory the fizz-detecting cells and the enzyme that make it all possible.

Jayaram Chandrashekar of the University of California, San Diego, and colleagues used a combination of electrophysiological measurements and genetic manipulation to show that the fizz detectors are in sour-sensing cells in the tongue. They are based on an enzyme, carbonic anhydrase 4, that turns carbon dioxide in water into a bicarbonate ion and a proton.

The enzyme is one of several targeted by acetazolamide, a drug used to protect against altitude sickness. Back in 1988 users had noted that it made fizzy beverages taste flat, thus making drinking champagne at the tops of high mountains a disappointment for anyone taking the drug.