Myeloperoxidase found in neutrophils

Peroxidases. Another group of enzymes, which is involved in the oxidation of xenobiotics, is the peroxidase. There are a number of these enzymes in mammalian tissues prostaglandin synthase found in many tissues, but especially seminal vesicles and also the kidney, the lung, the intestine spleen, and blood vessels lactoperoxidase found in mammary glands myeloperoxidase found in neutrophils, macrophages, liver Kupffer cells, and bone marrow cells. 

The heme iron in the peroxidase is oxidized by the peroxide from III+ to V4- in compound I. The compound I is reduced by two sequential one-electron transfer processes giving rise to the original enzyme. A substrate-free radical is in turn generated. This may have toxicological implications. Thus the myeloperoxidase in the bone marrow may catalyze the metabolic activation of phenol or other metabolites of benzene. This may underlie the toxicity of benzene to the bone marrow, which causes aplastic anemia (see below and chap. 6). The myeloperoxidase found in neutrophils and monocytes may be involved in the metabolism and activation of a number of drugs such as isoniazid, clozapine, procainamide, and hydralazine (see below). In in vitro systems, the products of the activation were found to be cytotoxic in vitro. 

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