Catalase-peroxidase (EC 1.11.1.21, katG (gene)) is an enzyme with systematic name donor:hydrogen-peroxide oxidoreductase. This enzyme catalyses the following chemical reaction 1. * donor + H2O2 ⇌ oxidized donor + 2 H2O 2. * 2 H2O2 ⇌ O2 + 2 H2O This enzyme is a strong catalase with H2O2 as donor which releases O2.