Table 1.

Nitric Oxide Synthase (NOS) Isoforms

NOS isoform	Location	Function	Cytosolic/membrane-associated?	Characteristics of enzymatic activity
Endothelial NOS (eNOS)	Endothelial tissue of blood vessels	Vasodilation and relaxation of muscles and soft tissue	Membrane-associated	Produces low concentrations of NO over long periods
Neuronal NOS (nNOS)	Central and peripheral neurons	Cell-to-cell communication	Cytosolic	Produces low concentrations of NO over long periods
Inducible NOS (iNOS)	Immune cells and glial cells	Mediate cell death in response to pathogens	Cytosolic	Produces high concentrations of NO over short periods
Mitochondrial NOS (mtNOS)	Mitochondrial inner membrane	Ca2+ regulation	Membrane-associated	Part of Ca2+ feedback loop