Reactive Oxygen Species

Synonyms

Reduced oxygen species

Definition

Reactive oxygen species are formed by the partial reduction of molecular oxygen (O₂) by enzymatic processes and the interactions of these species with each other and transition metals to produce more reactive oxygen species.

Discussion

Oxidative damage to DNA is discussed in the entry of the same title, and this entry will deal with the background on the reactive forms of oxygen and how they are formed.

In its native state, O₂ is in the triplet state (³O₂) and not prone to react with organic molecules, almost all of which are in the singlet state. However, O₂ is readily reduced by a number of enzyme systems (Fig. 1).

Fig. 1

(a) Reactions involved in the generation of reactive oxygen species and enzymatic systems for the prevention of damage. (b) Reactive nitrogen species