Superoxide (O₂^·−) is a biologically dangerous byproduct of cellular respiration in mitochondria. However, superoxide also serves as a first line of defense of the human immune system against bacterial invaders. We have functionally and structurally characterized a membrane protein in Escherichia coli that catalyzes a so far unknown biochemical reaction, the oxidation of superoxide to oxygen and the reduction of ubiquinone (UQ) to ubiquinol (UQ-H₂).

2 O₂^·− + UQ + 2H⁺   →   2 O₂ + UQ-H₂

This is only the third enzyme known to specifically react with superoxide.

This work was carried out in collaboration with the Högbom lab at Stockholm University and the von Ballmoos lab.

References:

• C. A. K. Lundgren, D. Sjöstrand, O. Biner, M. Bennett, A. Rudling, A.-L. Johansson, P. Brzezinski, J. Carlsson, C. von Ballmoos, M. Högbom;
  "Scavenging of superoxide by a membrane-bound superoxide oxidase"
  Nature Chem. Biol., 2018, 14(8), 788-793; doi:10.1038/s41589-018-0072-x.