Nitrous oxide (N2O), perhaps better known as laughing gas, is a dangerous greenhouse gas with nearly three hundred times more potency to trap heat than carbon dioxide. Nitrous oxide is cause for alarm because it accounts for approximately 10% of global greenhouse gases and contributes to global warming while at the same time depleting the ozone layer.
Atmospheric levels of nitrous oxide are on the rise and the major reason is the increasingly widespread use of synthetic nitrogen fertilizers in agriculture. As microorganisms break down synthetic nitrogen fertilizers, nitrous oxide is released into the atmosphere, where it stays for up to 120 years.
Yet new research published recently in the journal Chemical Science has discovered particular soil bacteria that create an enzyme – until now, the only known existing – that is capable of breaking down the gas. The study comes from the University of East Anglia (UEA).
Professor Nick Le Brun from UEA's School of Chemistry, said: "It is well known that some bacteria can 'breathe' N2O in environments where oxygen (O2) is limited. This ability is entirely dependent on an enzyme called 'nitrous oxide reductase', which is the only enzyme known to destroy N2O. It is therefore very important for controlling levels of this climate-changing gas. We wanted to find out more about how soil bacteria use this enzyme to destroy nitrous oxide."
Nitrous oxide reductase is special in the structure of its active site, which is where it consumes the nitrous oxide. Made up of a copper-sulfide cluster, its structure is complex and up until now, scientists had previously not understood the mechanisms needed in order to make the enzyme active. But the research team’s findings show that a protein called NosL is the key to making the enzyme active.
Professor Le Brun said: "The discovery of the function of NosL is the first step towards understanding how the unique active site of nitrous oxide reductase is assembled. This is key information because when assembly goes wrong, inactive enzyme leads to release of N2O into the atmosphere."
The researchers hope that the discovery of NosL and its function in nitrous oxide reductase will lead to further research that will tackle climate change and greenhouse gases in their full scope.
Dr. Andy Gates, from UEA's School of Biological Sciences, also collaborated on the research and commented that nitrous oxide often doesn’t receive the attention it should: "Society is generally well aware of the need to address carbon dioxide emissions, but nitrous oxide is now emerging as a pressing global concern and requires researchers with different skill sets to work together to prevent further damaging effects of climate change.
"With increasing understanding of the enzymes that make and destroy N2O, we move closer to being able to develop strategies to mitigate the damaging effects of this climate changing gas on the earth's environment."