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Nitric Oxide Synthases

Nitric oxide synthases (NOS) are enzymes that synthesize nitric oxide from the terminal nitrogen atom of L-arginine, provided oxygen is present for the synthesis. It allows for oxydation, in other words. In addition to oxygen, and L-arginine, nitric oxide synthesis must have present the following cofactors: nicotinamide adenine dinucleotide phosphate, or NADPH, flavin adenine dinucleotide, or FAD, flavin mononucleotide, or FMN, heme, and tetraydrobiopterin, or BH4. Most of these cofactors are present naturally.

There are three basic forms of nitric oxide synthase:

• Neuronal nitric oxide synthase (nNOS or NOS1) produces nitric oxide in neuronal tissue in the central and peripheral nervous systems, and performs an important role in intracellular communication.


• Inducible nitric oxide synthase (iNOS or NOS2) uses nitric oxide to put oxidative stress on pathogens.


• Macrophages use this in immunodefensive manners, and the same nitric oxide synthase can be found in the cardiovascular system.


• Entothelial nitric oxide syntase (eNOS or NOS3) plays a role in the regulation of vascular function. It generates nitric oxide in blood vessels.

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