Nitric oxide reductase which is involved in a dissimilatory reduction of nitrite. Acts as a nitric oxide reductase. Is able to reduce nitrate and nitrite to a gaseous form of N(2)O when oxygen supply is limited or discontinued. May function as a detoxification mechanism. H2O + NADP(+) + nitrous oxide = H(+) + NADPH + 2 nitric oxide H2O + NAD(+) + nitrous oxide = H(+) + NADH + 2 nitric oxide Cyanide, CO, and oxygen strongly inhibit catalytic activity. By nitrate/nitrite. Belongs to the cytochrome P450 family.