Endothelial nitric oxide synthase and Inducible nitric oxide synthase (eNOS/iNOS)

Nitric oxide synthases (NOS) are a family of enzymes that catalyze the production of nitric oxide (NO) from L-arginine (UniProt P29474, P35228). This entry encompasses two distinct isoforms: Endothelial nitric oxide synthase (eNOS or NOS3) and Inducible nitric oxide synthase (iNOS or NOS2). eNOS is primarily expressed in the vascular endothelium, where it produces NO to maintain vascular tone, inhibit platelet aggregation, and regulate blood pressure (StatPearls, Physiology, Nitric Oxide). iNOS is typically induced in response to inflammatory stimuli, such as cytokines or endotoxins, and produces significantly higher amounts of NO as a defense mechanism against pathogens (PubMed PMID 7531153). While eNOS activity is generally protective for the cardiovascular system, excessive iNOS activity is implicated in the pathogenesis of septic shock, chronic inflammation, and certain cancers (PubMed PMID 11544102). Pharmacological targeting of these enzymes involves inhibitors that compete with L-arginine or cofactors like tetrahydrobiopterin. Therapeutic development focuses on achieving isoform selectivity, particularly for iNOS, to treat inflammatory conditions without causing the hypertensive side effects associated with eNOS inhibition (PubMed PMID 9154002).

Other names

NOS3NOS2Nitric oxide synthase 3Nitric oxide synthase 2Endothelial NOSInducible NOSNOS IIINOS II

Competitive inhibition of the L-arginine binding site or interference with essential cofactors like tetrahydrobiopterin (BH4) to prevent the conversion of L-arginine to L-citrulline and nitric oxide (PubMed PMID 11544102).