That's pretty much the classic diagnostic test for aerobic bacteria- add H202 and watch it fizz. Anything that "breathes" oxygen has it in spades, since peroxide is formed in huge amounts as a side product. If organisms (including animals and plants) didn't have a way to deal with it, they'd off themselves fairly quickly.
Superoxide dismutase and catalase. Don't respire without them!
Glad to see someone else here with a basic understanding of the enzymatic decomposition of peroxides