Nitrogen cycle enzymology.

The minimal nitrogen cycle involves five reduction reactions and three oxidation reactions, each of which poses interesting problems in bioinorganic chemistry, energy transduction and protein structure/function relationships. Many of the major recent developments in this field have depended on the acquisition of protein crystal structures, including structures of enzymes with bound substrates or products and in protein-protein complexes. These enzymes include nitrogenase, nitrite reductases, hydroxylamine oxidoreductase and a fungal nitric oxide reductase.