SOD1 also has peroxidase activity, and this peroxidase activity is enhanced in mutant SOD1 compared to normal SOD1 (110). This gain-of-function augments the production of hydroxyl and superoxide radicals, and possibly the formation of peroxynitrite by the combination of superoxide and NO (108,110). These altered properties of mutant SOD1 have not yet been causally linked specifically to motor neuron damage in ALS.