NADPH + 2 nitric oxide + 2 O2 = H(+) + NADP(+) + 2 nitrate NADH + 2 nitric oxide + 2 O2 = H(+) + NAD(+) + 2 nitrate Binds 1 heme b (iron(II)-protoporphyrin IX) group per subunit. Binds 1 FAD per subunit. Consists of two distinct domains; an N-terminal heme-containing oxygen-binding domain and a C-terminal reductase domain with binding sites for FAD and NAD(P)H. Belongs to the globin family. Two-domain flavohemoproteins subfamily. In the C-terminal section; belongs to the flavoprotein pyridine nucleotide cytochrome reductase family.