superoxidreduktaser

Superoxidreduktaser, or superoxide reductases, are enzymes that catalyze the one-electron reduction of the reactive oxygen species superoxide to hydrogen peroxide. The typical reaction is O2− + e− + 2 H+ → H2O2, with electrons supplied by small redox carriers such as rubredoxin. This mechanism contrasts with that of superoxide dismutases (SODs), which convert two superoxide molecules into oxygen and hydrogen peroxide.

Most characterized SORs are rubredoxin-dependent and are found primarily in strict anaerobes or microaerophilic microorganisms, including many bacteria and some archaea. In environments where oxygen partially penetrates, SORs help limit oxidative damage by converting superoxide to hydrogen peroxide, which can then be further processed by other enzymes such as catalases or peroxidases. The presence of SORs is often associated with organisms that experience transient exposure to oxygen or that rely on anaerobic metabolism.

Structurally, SORs contain a mononuclear non-heme iron center at the active site that cycles between oxidation states during turnover. The enzyme receives electrons from rubredoxin or other electron carriers, delivering them to the iron center to reduce bound superoxide to hydrogen peroxide. The overall fold and exact ligands around the iron center can vary among SOR families, but the core feature is a soluble protein that houses a reactive iron site capable of facilitating single-electron transfer to superoxide.

Biological significance and research interest in SORs stem from their role in oxidative stress defense in organisms lacking typical SOD systems, as well as from their contribution to our understanding of non-heme iron chemistry and rubredoxin-dependent electron transfer networks. They are also explored for insights into engineering microbial tolerance to reactive oxygen species.