A team of UK researchers has helped uncover the mystery of exactly how soil bacteria catalyse the reduction of nitrous oxide.
A team of UK researchers has helped uncover the mystery of exactly how soil bacteria catalyse the reduction of nitrous oxide, N2O, to nitrogen gas.
N2O is an important greenhouse gas which contributes to global warming. Experiments designed to understand how it is released into the atmosphere have gathered pace in recent years.
N2O reduction is the final stage in the denitrification process that converts soluble nitrate ions derived from artificial fertilisers into N2. An enzyme found in soil bacteria called nitrous oxide reductase (N2OR) catalyses the reduction of N2O to N2. The active site of N2OR is a copper-sulfide cluster that forms a complex with N2O. During the reduction process, electrons from one enzyme molecule transfer to a copper-N2O complex on another.
N2O reduction starts when one of the enzyme sites is fed electrons from an outside donor, in this case a molecule called cytochrome c (Cyt c).
A team of investigators, led by Andrew Thomson at the University of East Anglia, measured the rates of electron transfer between Cyt c and the active site of N2OR to help understand the precise reduction mechanism.
Thomson discovered that the transfer of electrons from Cyt c to the enzyme pair takes place only after a short time lag.
The time delay can be explained by a small but important structural change that happens when Cyt c approaches the enzyme pair. Without this structural change, electron transfer is not possible and the reduction of N2O slows dramatically.
The model is still hypothetical, but Thomson thinks it might help solve the riddle of why N2OR reduces N2O in such a controlled manner.