Abstract

Most aerobic organisms are exposed to oxidative stress, which results in the generation of free reactive oxygen species (superoxide, hydrogen peroxide, hydroxyl radical) that interfere with the cell’s metabolism, cause oxidative damage of cellular macromolecules, and may eventually also cause cell death. Thus, eliminating these free oxygen radicals is absolutely mandatory for cell survival. In this context, catalases are antioxidant enzymes that accelerate the rate of hydrogen peroxide decomposition to molecular oxygen and water with near kinetic perfection. Exhibiting one of the highest known turnover numbers, a catalase molecule can convert approximately 4 × 107 substrate molecules to the referred products each second. The catalytic efficiency (kcat/Km) of catalase (4.0 × 108 M−1 s−1) is very high indeed. Because the efficiency is at the diffusion limit, catalase is said to have achieved “