Lactoperoxidase

Lactoperoxidase is a peroxidase enzyme secreted from mammary, salivary and other mucosal glands including the lungs, bronchii and nose that functions as a natural and the first line of defense against bacteria and viruses. Lactoperoxidase is a member of the heme peroxidase family of enzymes. In humans, lactoperoxidase is encoded by the LPO gene.

Lactoperoxidase catalyzes the oxidation of several inorganic and organic substrates by hydrogen peroxide. These substrates include bromide and iodide and therefore lactoperoxidase can be categorised as a haloperoxidase. An other important substrate is thiocyanate. The oxidized products produced through the action of this enzyme have potent and non-specific bactericidal and antiviral activities, including destruction of the influenza virus. Lactoperoxidase together with its inorganic ion substrates, hydrogen peroxide, and oxidized products is known as the lactoperoxidase system. Hence LPO is considered a very important defense against invasive bacteria and viral agents such as influenza and the SARS-CoV-2 virus when sufficient iodine is provided.

The lactoperoxidase system plays an important role in the innate immune system by killing bacteria in milk and mucosal (linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion) secretions hence augmentation of the lactoperoxidase system may have therapeutic applications. Furthermore, addition or augmentation of the lactoperoxidase system has potential applications in controlling bacteria in food and consumer health care products. The lactoperoxidase system does not attack DNA and is not mutagenic. However, under certain conditions, the lactoperoxidase system may contribute to oxidative stress. Furthermore, lactoperoxidase may contribute to the initiation of breast cancer, through its ability to oxidize estrogenic hormones producing free radical intermediates.