Purification and characterization of the single‐component nitric oxide reductase from Ralstonia eutropha H16

Abstract
Nitric oxide (NO) reductase was purified from Ralstonia eutropha (formerly Alcaligenes eutrophus) using a two step chromatographic procedure. Unlike the common NO reductases, the enzyme consists of a single subunit of 75 kDa which contains both high‐spin and low‐spin heme b, but lacks heme c. One additional iron atom, probably a ferric non‐heme iron, was identified per enzyme molecule. Whereas reduced cytochrome c was ineffective as electron donor, NO was reduced at a specific activity of 2.3 μmol/min per mg of protein in the presence of 2‐methyl‐1,4‐naphthoquinol.