Anaerobic purification and characterization of nitrous oxide reductase from Rhodobacter sphaeroides f. sp. denitrificans IL106

The nitrous oxide reductase from the photodenitrifier, Rhodobacter sphaeroides f. sp. denitrificans IL106, has been purified under anaerobic conditions. The specific activity of the enzyme was 78 micromol nitrous oxide reduced per min per mg protein, which was approximately 80% higher than that of the aerobic form. The enzyme purified anaerobically retained most of its activity after aerobic storage at 4 degrees C for 2 months without any additives. Visible absorption spectra of the Rhodobacter nitrous oxide reductase resembled those of the enzymes from other origins. The enzyme retained its activity after reduction with sodium dithionite, and the enzyme activity could be determined using dithionite-reduced benzyl viologen. Turnover-dependent inactivation of the enzyme was suppressed by complete removal of oxygen from the reaction mixture, and promoted by zinc ions.