Peroksydaz

Peroksydaz, or peroxidases, are a broad family of enzymes that catalyze oxidation reactions using hydrogen peroxide as the oxidant. They occur in nearly all organisms and participate in processes such as lignin formation in plants, defense against pathogens, hormone metabolism, and detoxification of reactive oxygen species.

Classification and examples: The best-known are heme-containing peroxidases. Plant secretory peroxidases (class III) function in the apoplast and cell wall formation; fungal lignin peroxidases (LiP) and manganese peroxidases (MnP) contribute to lignin modification and degradation; vertebrate enzymes include myeloperoxidase. Bacterial peroxidases add further diversity. Horseradish peroxidase (HRP) is among the most widely used laboratory enzymes.

Mechanism: Peroxidases use a heme cofactor and cycle between ferric (Fe3+) resting state and reactive intermediates (Compound I and II) to oxidize various substrates while reducing H2O2 to water.

Functions and roles: In plants, peroxidases contribute to lignin and suberin formation, reinforce cell walls, and participate in defense responses. In animals, certain peroxidases participate in microbial killing and signaling; in microbes, they help cope with oxidative stress and metabolize peroxides.

Applications: In biotechnology, HRP and related enzymes are used in ELISA, Western blot, and immunohistochemistry. Peroxidases are also employed in biosensors, polymerization processes, and bioremediation of pollutants.

Properties: Activity depends on pH and temperature; excess H2O2 can inactivate enzymes. Inhibitors include cyanide and azide; stability and substrate specificity vary among families.