Climate change and ozone destruction hastened with nitrous oxide used in agriculture

Researchers have discovered a new binding site for nitrous oxide (N2O). Nitrous oxide reductase, an enzyme containing copper, plays a key role in the biochemical process by reducing N2O to N2. This enzyme is highly sensitive to oxygen and is often precipitated in the reaction chain, meaning large amounts of N2O are released by fertilised fields in the farming industry.

Nitrous oxide (N2O) harms Earth's climate in two ways. First, N2O is a colourless and odourless greenhouse gas that is 300 times stronger than carbon dioxide (CO2). Second, under the effect of cosmic radiation, it contributes to the destruction of the ozone layer, like halocarbons, or chlorofluorocarbons (CFCs).

N2O is therefore probably the most critical greenhouse gas of the 21st century and is an unwanted by-product of industrial farming. Nitrous oxide reductase, an enzyme containing copper, plays a key role in the biochemical process by reducing N2O to N2. This enzyme is highly sensitive to oxygen and is often precipitated in the reaction chain, meaning large amounts of N2O are released by fertilised fields in the farming industry.

The functionality and mechanisms of this important enzyme had not been thoroughly researched until Dr Anja Pomowski successfully clarified the structure of a N2O reductase, primed under the strict exclusion of dioxygen (O2). Dr Pomowski belongs to the research group headed by Prof Dr Oliver Einsle, a professor at the Institute of Organic Chemistry and Biochemistry of the University of Freiburg and a member of the BIOSS Cluster of Excellence. Together with Prof Dr Walter Zumft from the Karlsruhe Institute of Technology and Prof Dr Peter Kroneck from the University of Konstanz, the team of researchers is presenting their results in the current issue of the journal Nature.

The newly discovered structure shows first that the ratio and amount of substances in the metal centre of the enzyme have only been described incompletely thus far, and that they contain an additional sulphur atom. Second, the team also identified the binding of the N2O substrate to the metal centre. This binding site was a surprise to the scientists, and it has encouraged them to re-evaluate the mechanisms of the enzyme, whose molecular properties Prof Dr Oliver Einsle's group will continue to research in the future.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Albert-Ludwigs-Universität Freiburg.

Journal Reference:

Anja Pomowski, Walter G. Zumft, Peter M. H. Kroneck, Oliver Einsle. N2O binding at a [4Cu:2S] copper–sulphur cluster in nitrous oxide reductase. Nature, 2011; DOI: 10.1038/nature10332