Analysis Note

Protein determined by biuret

Biochem/physiol Actions

Each subunit of the tetramer contains iron bound to a protoheme IX group. The enzyme also strongly binds NADP, which is in close proximity to the heme group. Catalase activity is constant over the pH range of 4.0-8.5. The pI is found to be 5.4. Optimum pH for catalytic activity is 7.0. The enzyme activity is inhibited by 3-amino-1-H-1,2,4 triazole, cyanide, azide, hydroxylamine, cyanogen bromide, 2-mercaptoethanol, dithiothreitol, dianisidine, and nitrate. Incubation of catalase with ascorbate or ascorbate/Cu2+ results in degradation of the catalase molecule.

Catalase activates the decomposition of hydrogen peroxide, a reactive oxygen species, into water and oxygen. It functions as a natural antioxidant, protecting cells against oxidative damage to proteins, lipids and nucleic acids. Catalase has also been used to study the role reactive oxygen species play in gene expression and apoptosis.

Physical form

Solution in 50 mM Tris, pH 8.0

Unit Definition

One unit will decompose 1.0 µmole of H₂O₂ per min at pH 7.0 at 25 °C, while the H₂O₂ conc. falls from 10.3 to 9.2 mM, measured by the rate of decrease of A₂₄₀.