Figure 1.

Cellular detoxification of reactive oxygen and nitrative species. Oxygen is reduced to superoxide (O₂⁻) during inflammation, and nitric oxide (NO⁻) is generated by the action of inflammatory nitric oxide synthase (iNOS) on L-arginine. In the absence of detoxifying enzymes, NO⁻ and O₂⁻ react to produce the highly toxic peroxynitrite (ONOO⁻). Superoxide dismutase (SOD) competes for the superoxide anion and dismutes it to form hydrogen peroxide (H₂O₂) which can then be removed by the enzymes catalase and glutathione peroxidase (GPX).