NO Synthase is an enzyme in the body that contributes to transmission from one neuron to another, to the immune system and to dilating blood vessels. It does so by synthesis of nitric oxide from the terminal nitrogen atom of L-arginine in the presence of NADPH and dioxygen. NOS is the only known enzyme that binds flavin adenine dinucleotide, flavin mononucleotide, heme, tetrahydrobiopterin and calmodulin.