The<unk>  <unk> ; EC 1.14.13.39) 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<unk><unk>  (NO) from the terminal nitrogen atom of L-arginine in the presence of NADPH and dioxygen (O2).<unk>  is the only known enzyme that binds flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), heme, tetrahydrobiopterin (BH4) and calmodulin.<unk>  activates Cyclic GMP, which induces smooth muscle relaxation by multiple mechanisms including: 1. increased intracellular cGMP, which inhibits calcium entry into the cell, and decreases intracellular calcium concentrations 2. activates K+ channels, which leads to hyperpolarization and relaxation 3.  stimulates a cGMP-dependent protein kinase that activates myosin light chain phosphatase, the enzyme that dephosphorylates myosin light chains, which leads to smooth muscle relaxation.
Nitric oxide synthase
Adenylate cyclase
Adenylate kinase
Alternative oxidase
Metalloproteinases 
Ubiquinol oxidase
Janus kinase
Sodium calcium exchanger