from David Richardson writing in Nitrogen Cycling in Bacteria: Molecular Analysis:
The redox reactions of the nitrogen cycle comprise a large number of oxidative and reductive reactions that are catalysed by wide variety of enzymes with different catalytic centres. These enzymes are frequently organised as multi-protein complexes and in some recently emerging cases enzymes catalysing different reactions of the N-cycle appear to form super-complexes. This review will survey some of these N-cycle protein complexes.
Further reading: Nitrogen Cycling in Bacteria: Molecular Analysis