New research from the University of East Anglia reveals how soil bacteria build the only kno

wn enzyme for the destruction of the potent global warming and ozone-depleting gas nitrous 

oxide.

Alongside carbon dioxide (CO2) and methane, the greenhouse gas nitrous oxide (N2O), 

commonly known as 'laughing gas', is now a cause for great concern, and there is much 

international focus on reducing emissions.

It is hoped that the findings, published today in the journal Chemical Science, will help pave 

the way for strategies to mitigate the damaging effects of this climate changing gas.

N2O has around 300 times the global warming potential of CO2 and stays in the atmosphere 

for about 120 years, where it accounts for around nine per cent of total greenhouse gas.

It also destroys the ozone layer with similar potency to the now banned chlorofluorocarbons 

(CFCs).

Atmospheric levels of N2O are rising year on year as microorganisms break down synthetic 

nitrogen fertilisers which are added to agricultural soil, to satisfy the food supply demands of 

an ever-increasing global population.

Prof 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."

The part of the enzyme where N2O is consumed (called the 'active site') is unique in biology, 

consisting of a complex arrangement of copper and sulfur (a copper-sulfide cluster). Until 

now, knowledge of how this unusual active site is built by bacteria has been lacking.

The UEA team discovered a protein called NosL, which is required for the assembly of the 

copper-sulfide cluster active site and makes the enzyme active.

They found that bacteria lacking NosL still produced the enzyme but it contained less of the 

copper-sulfide active site. Furthermore, when the same bacteria were grown with copper in 

short supply, the active site was completely absent from the enzyme.

The team also showed that NosL is a copper-binding protein, indicating that it functions 

directly  in  supplying  copper  for  the assembly of the copper - sulfide c luster  active site.

Prof  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."