Comparative electrochemical study of superoxide reductases.

Superoxide reductases are involved in relevant biological electron transfer reactions related to protection against oxidative stress caused by reactive oxygen species. The electrochemical features of metalloproteins belonging to the three different classes of enzymes were studied by potentio-dynamic techniques (cyclic and square wave voltammetry): desulfoferrodoxin from Desulfovibrio vulgaris Hildenborough, class I superoxide reductases and neelaredoxin from Desulfovibrio gigas and Treponema pallidum, namely class II and III superoxide reductases, respectively. In addition, a small protein, designated desulforedoxin from D. gigas, which has high homology with the N-terminal domain of class I superoxide reductases, was also investigated. A comparison of the redox potentials and redox behavior of all the proteins is presented, and the results show that SOR center II is thermodynamically more stable than similar centers in different proteins, which may be related to an intramolecular electron transfer function.