MPO Human

Myeloperoxidase is encoded by the MPO gene located on chromosome 17 in humans . The enzyme is a lysosomal protein stored in azurophilic granules of neutrophils and is released into the extracellular space during degranulation . The enzyme contains a heme pigment, which gives it a green color in secretions rich in neutrophils, such as mucus and sputum .

MPO catalyzes the production of hypochlorous acid from hydrogen peroxide and chloride ions during the neutrophil’s respiratory burst . This reaction is essential for the microbial killing activity of neutrophils. Additionally, MPO can oxidize tyrosine to form tyrosyl radicals, which are cytotoxic and help in killing bacteria and other pathogens .

Myeloperoxidase deficiency is a documented condition that results in impaired immune function . The enzyme is also involved in various inflammatory processes and has been linked to diseases such as atherosclerosis and certain types of vasculitis . MPO antibodies, known as antineutrophil cytoplasmic antibodies (ANCAs), are useful in diagnosing vasculitis .

The presence of myeloperoxidase was first recognized in 1868 when it was observed that guaiac tincture, a substance used for peroxidase activity assays, could be oxidized by pus, suggesting the existence of MPO in leukocytes .

Recent studies have shown that myeloperoxidase is the first human enzyme known to break down carbon nanotubes, which has implications for the use of nanotubes in targeted drug delivery . The enzyme’s role in oxidative stress and inflammation continues to be a significant area of research, particularly in understanding its contribution to chronic diseases .

Myeloperoxidase remains a critical enzyme in the study of immunology and pathology, with ongoing research aimed at uncovering its full range of functions and potential therapeutic applications.