katalase

Catalase is an enzyme that catalyzes the decomposition of hydrogen peroxide into water and molecular oxygen. It is found in almost all aerobic organisms and serves to protect cells from oxidative damage caused by hydrogen peroxide produced during metabolism and immune responses.

In most eukaryotes, catalase is a homotetramer containing a heme prosthetic group. Each subunit binds a heme iron that cycles through oxidized and reduced states during turnover. The enzyme is typically localized in peroxisomes in animal cells, reflecting its role in detoxifying hydrogen peroxide generated in peroxisomal reactions; in plants, catalase can be found in peroxisomes as well as other cellular compartments.

Bacteria and archaea also possess catalases, including classical catalases and catalase–peroxidases (KatG). Some organisms have manganese-containing catalases, a distinct class. There are isoforms in certain species with differing regulatory properties and cellular localization, reflecting adaptation to various environments.

The catalytic reaction is 2 H2O2 → 2 H2O + O2. The mechanism involves a heme-centered cycle that rapidly converts hydrogen peroxide, often via high-valence intermediates, enabling very high turnover numbers compared with many other enzymes.

In humans, the CAT gene encodes catalase. Mutations or defects can lead to reduced activity or mislocalization; acatalasia is a rare inherited condition characterized by very low or absent catalase activity. Catalase activity can be influenced by pH and temperature and can be inhibited by agents such as cyanide.

Industrial and laboratory uses include removing residual hydrogen peroxide from solutions, in food and textile processing, and as a diagnostic reagent.