Isolation of a peroxidatically active product from the peptic digest of ox-liver catalase and some of its properties.

1. A homogeneous peroxidatically active product has been isolated from a peptic digest of ox-liver catalase. 2. The nitrogen and the iron contents of the ;active product' are 15.3% and 0.21% respectively. 3. The S(0) (20,w) and molecular weight of the ;active product' are 2.6s and 27500 respectively. 4. The ;active product' contains 248 amino acid residues/mol. assuming a mol.wt. of 27500. 5. The properties of the ;active product' and catalase are compared and the relationship between their structures and enzyme activity is discussed.