Coordinate expression of the enzymes of nitric oxide metabolism in Paracoccus denitrificans.

Cellular activities of nitric oxide producing nitrite reductase (NiR) and nitric oxide reductase (NOR) in Paracoccus denitrificans increased in parallel upon anaerobic adaptation of aerobically grown cells. In addition, both activities exhibited comparable dependences on oxygen supply into the growing culture. The results suggest that the maintenance of a sufficiently high NOR/NiR activity ratio plays an important role in preventing nitric oxide accumulation and its toxic effects on the cells during denitrification.