Catalaseperoxidases

Catalaseperoxidases, often abbreviated as KatGs, are a class of enzymes that possess both catalase and peroxidase activities. These bifunctional enzymes are found in various bacteria, fungi, and even some protozoa. Their primary role in these organisms is to protect cells from oxidative damage caused by reactive oxygen species. Catalase activity allows them to decompose hydrogen peroxide into water and oxygen, while their peroxidase activity enables them to oxidize a broader range of substrates using hydrogen peroxide as an oxidant.

The catalytic mechanism of catalaseperoxidases is complex, involving a heme prosthetic group at the active site. This heme iron undergoes various oxidation states during the enzymatic cycle, facilitating the transfer of electrons and oxygen atoms. The dual functionality is thought to arise from structural features that allow for distinct substrate access and reaction pathways within the same active site.

Catalaseperoxidases play significant roles in microbial physiology. In pathogenic bacteria like Mycobacterium tuberculosis, KatG is crucial for virulence. It confers resistance to the oxidative burst produced by host immune cells. Furthermore, KatG is involved in the activation of the isoniazid prodrug, a cornerstone of tuberculosis treatment. The study of catalaseperoxidases is important for understanding microbial survival strategies and for developing new antimicrobial therapies.