The cytochrome cbb3 from Pseudomonas stutzeri displays nitric oxide reductase activity

The cytochrome cbb(3) is an isoenzyme in the family of cytochrome c oxidases. This protein purified from Pseudomonas stutzeri displays a cyanide-sensitive nitric oxide reductase activity (V-max=100 +/-9 mol NO.mol cbb(3)(-1).min(-1) and K-m=12 +/-2.5 mum), which is lost upon denaturation. This enzyme is only partially reduced by ascorbate, and readily re-oxidized by NO under anaerobic conditions at a rate consistent with the turnover number for NO consumption. As shown by transient spectroscopy experiments and singular value decomposition (SVD) analysis, these results suggest that the cbb(3)-type cytochromes, sharing structural features with bacterial nitric oxide reductases, are the enzymes retaining the highest NO reductase activity within the heme-copper oxidase superfamily.