any of a group of enzymes that catalyse the oxidation of a compound by the decomposition of hydrogen peroxide or an organic peroxide. They generally consist of a protein combined with haem
peroxidase per·ox·i·dase (pə-rŏk'sĭ-dās', -dāz') n. Any of a group of enzymes that occur especially in plant cells and catalyze the oxidation of a substance by a peroxide.