The findings, by Professor Paul Kemp of the Cardiff School of Biosciences, and colleagues at both Cardiff and Leeds Universities, will be published in the journal Science later this month.
"The discovery could have important implications for understanding how the body adjusts to major changes in oxygen levels, such as when babies are born or following a stroke," said Professor Kemp. "It will certainly lead to the development of new therapeutic strategies aimed at maximising oxygen delivery when and where it is needed most."
The scientists have identified an oxygen-sensing protein, which in mammals is located in a cluster of cells at the spot where the carotid artery branches in the neck. It senses oxygen levels in the blood flowing by and helps the brain to adjust the breathing rate accordingly.
"When oxygen becomes scarce, channels on these cells become less active, causing a cascade of signals that ultimately increases ventilation," explained Professor Kemp. "Until now, it has been unclear exactly how these channels sense oxygen."
The scientists discovered that the oxygen-sensing molecule is the enzyme "hemoxygenase-2". Under normal conditions, this enzyme uses oxygen to generate carbon monoxide. Under low-oxygen conditions, the enzyme produces less carbon monoxide, thus inhibiting the channels and triggering the signal to increase ventilation.