Myeloperoxidase (MPO)

Myeloperoxidase (MPO) is a hemoprotein that is abundantly expressed in polymorphonuclear leukocytes (neutrophils) and secreted during their activation. The presence of a peroxidase in the cytoplasmic granules of leukocytes was suggested at the beginning of 20th century but it was the early 1940s that it was purified for the first time.

Native MPO is a covalently bound tetrameric complex of two glycosylated alpha chains (MW 59 – 64 kDa) and two unglycosylated beta chains (MW 14 kDa) with total MW about 150 kDa and theoretical pI 9.2. MPO plays an important role in neutrophil microbicidal action through catalyzing chloride ion oxidation to hypochlorous acid, which is a potent antimicrobial agent.