Lactoperoxidase

Lactoperoxidase (LPO, ) is a peroxidase enzyme secreted from mammary, salivary, tears and other mucosal glands including the lungs, bronchii and nose that function as a natural, first line of defense against bacteria and viral agents. 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 many organic substrates by hydrogen peroxide. Lactoperoxidase rapidly oxidizes iodide and slowly oxidizes bromide and is designated a haloperoxidase. Another important substrate is the pseudo-halide thiocyanate. The oxidized products display potent, non-specific bactericidal and antiviral activities, including destruction of the influenza virus. Lactoperoxidase together with its inorganic ion substrates, hydrogen peroxide, DUOX1 and DUOX2 and products are termed 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.