Overview of the pathway and functions of nitric oxide.

Nitric oxide has been recognized for years as a toxic, reactive, free radical gas, but in recent years it has been identified as having functions in a variety of metabolic and signaling pathways. NO is synthesized, by nitric oxide synthase, on demand and diffuses to the site of action where it forms noncovalent and covalent linkages with target molecules. This overview presents the pathway of NO formation and also discusses the functions of NO in the nervous, immune and vascular systems.