Nitric Oxide Synthase - Classification

Classification

Different members of the NOS family are encoded by separate genes. NOS is one of the most regulated enzymes in biology. There are three known isoforms, two are constitutive (cNOS) and the third is inducible (iNOS). Cloning of NOS enzymes indicates that, cNOS include both brain constitutive (NOS1) and endothelial constitutive (NOS3), the third is the inducible (NOS2) gene. Recently, NOS activity has been demonstrated in several bacterial species, including such notorious pathogens as Bacillus anthracis and Staphylococcus aureus.

The different forms of NO synthase have been classified as follows:

Name Gene(s) Location Function
Neuronal NOS (nNOS or NOS1) NOS1, Chromosome 12
  • nervous tissue
  • skeletal muscle type II
  • cell communication
Inducible NOS (iNOS or NOS2) NOS2, Chromosome 17
  • immune system
  • cardiovascular system
  • immune defense against pathogens
Endothelial NOS (eNOS or NOS3 or cNOS) NOS3, Chromosome 7
  • endothelium
  • vasodilation
Bacterial NOS (bNOS) multiple
  • various Gram-positive bacteria
  • defense against oxidative stress, antibiotics, immune attack

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