Table 2

Isoforms of NOS

Endothelial NOS (eNOS)2-a(Type III NOS, NOS-3)Neuronal NOS (nNOS)2-a(Type I NOS, NOS-1, bNOS)Inducible NOS (iNOS)2-a(Type II NOS, NOS-2, macNOS, hepNOS)
Primary regulationCa2+/calmodulinCa2+/calmodulinGene expression
Subcellular locationMembrane ≫ cytosolCytosol?Cytosol ≫ membrane
NO output2-b Low (pmolar)Low (pmolar)High (μmolar)
FunctionCell signalingCell signalingCytotoxic
  • 2-a Previously used alternative abbreviation.

  • 2-b All three isolated purified isoforms of NOS have comparable specific activities. Output in this case refers to differences in levels of enzyme expression and in duration of activation in the in vivo situation.