Catalase is an enzyme, O2 and H2O are substrates, and H2O2 is a reactant.
Catalase is a substrate, O2 and H2O are substrates, and H2O2 is an enzyme.
Catalase is a substrate, O2 and H2O are products, and H2O2 is an enzyme.
Catalase is an enzyme, O2 and H2O are products, and H2O2 is a substrate.