genetically engineered to lack catalase completely, suffer few ill effects. [ 120 ] [ 121 ] Decameric structure of AhpC, a bacterial 2-cysteine peroxiredoxin from Salmonella typhimurium . [ 122 ] Peroxiredoxins are peroxidases that catalyze the reduction of hydrogen peroxide, organic hydroperoxides , as well as peroxynitrite . [ 123 ]