Aerobic ammonia-oxidizing archaea (AOA) play a crucial role in the global nitrogen cycle by oxidizing ammonia to nitrite, and nitric oxide (NO) is a key intermediate in AOA for sustaining aerobic ammonia oxidation activity. We herein heterologously expressed the NO-forming, copper-containing, dissimilatory nitrite reductase (NirK) from Nitrososphaera viennensis and investigated its enzymatic properties. The recombinant protein catalyzed the reduction of 15NO2– to 15NO, the oxidation of hydroxylamine (15NH2OH) to 15NO, and the production of 14-15N2O from 15NH2OH and 14NO2–. To the best of our knowledge, the present study is the first to document the enzymatic properties of AOA NirK.
Aerobic ammonia-oxidizing archaea (AOA) play a crucial role in the global nitrogen cycle by oxidizing ammonia to nitrite, and nitric oxide (NO) is a key intermediate in AOA for sustaining aerobic ammonia oxidation activity. We herein heterologously expressed the NO-forming, copper-containing, dissimilatory nitrite reductase (NirK) from Nitrososphaera viennensis and investigated its enzymatic properties. The recombinant protein catalyzed the reduction of 15NO2− to 15NO, the oxidation of hydroxylamine (15NH2OH) to 15NO, and the production of 14–15N2O from 15NH2OH and 14NO2−. To the best of our knowledge, the present study is the first to document the enzymatic properties of AOA NirK.