Myeloperoxidáza

Myeloperoxidáza, also known by its English designation myeloperoxidase (MPO), is a heme-containing peroxidase enzyme predominantly expressed in azurophilic granules of neutrophils and to a lesser extent in monocytes. It catalyzes the production of hypochlorous acid (HOCl) from hydrogen peroxide and chloride ion, a potent microbicidal oxidant that contributes to the bactericidal activity of neutrophil phagosomes. The enzyme plays a key role in innate immunity but may also contribute to tissue damage during inflammatory disorders.

The MPO protein consists of approximately 669 amino acids and contains a single catalytic site with a ferric heme group. The enzyme is secreted from neutrophils during degranulation and can be found bound to endothelial surfaces and in plasma during active inflammation. MPO activity is measured in research and clinical laboratories by chemiluminescent or spectrophotometric assays that monitor HOCl production.

Genetic polymorphisms in the MPO gene are associated with variations in enzyme activity and have been investigated for links to cardiovascular disease, atherosclerosis, and autoimmune conditions such as systemic lupus erythematosus. Elevated plasma MPO levels are considered a biomarker for coronary artery disease and can predict adverse cardiovascular events. MPO inhibitors are under study as potential therapeutics to reduce oxidative stress and inflammation in cardiovascular and chronic inflammatory diseases.

In summary, myeloperoxidáza is a key component of the respiratory burst in phagocytes, instrumental for microbial killing but also implicated in oxidative tissue injury. Its clinical significance is reflected in its use as a biomarker for cardiovascular risk and as a target for antioxidant therapy.