ABSTRACT
Catalase and peroxidase differ markedly in their protein characteristics but have some common features in their mechanism of action. Catalase is found in animals, plants, and microorganisms and has been purified from all three sources. Crystalline beef liver catalase was first prepared by James B. Sumner and A. L. Dounce in 1937 and the enzyme has been crystallized from several other sources since that time. When low concentrations of hydrogen peroxide are added to catalase, there is formation of a spectrally different compound that resembles very closely that of Compound I of peroxidise. Peroxidase is widely distributed in higher plants, with especially high concentrations in fig sap and horseradish. In 1943, Theorell crystallized horseradish peroxidase; the enzyme has been crystallized from some other sources. The ferroprotoporphyrin group includes peroxidases from higher plants, animals, and microorganisms. Catalase can catalyze two types of reactions, a catalatic and a peroxidatic reaction.
