Scavenging of H202 and Production of Oxygen by Horseradish ~eroxidase'

Peroxidases catalyze many reactions, the most com-mon being the utilization of H202 to oxidize numerous substrates (peroxidative mode). Peroxidases have also been proposed to produce H202 via utilization of NAD(P)H, thus providing oxidant either for the first step of lignification or for the "oxidative burst " associated with plant-pathogen interactions. The current study with horseradish peroxidase characterizes a third type of peroxidase activity that mimics the action of catalase; molecular oxygen is produced at the expense of H,O, in the absence of other reactants. The oxygen production and H202-scavenging activities had temperature coeffi-cients, Q,,, of nearly 3 and 2, which is consistent wit