Stimulation of KatG catalase activity by peroxidatic electron donors

► Peroxidatic electron donors stimulate KatG catalase activity by up to 14-fold. ► The stimulatory effect is optimal under conditions that favor peroxidase activity. ► The stimulatory mechanism produces minimal accumulation of oxidized electron donor. ► Aromatic amines are effective stimulators; phenols and ascorbate are not. ► An intermediate reminiscent of FeIII-O2− heme dominates during stimulated turnover.