402576113ENSG00000167419ENSMUSG00000009356P22079n/aNM_001160102NM_006151NM_080420NP_001153574NP_006142n/aLactoperoxidase (LPO, EC 1.11.1.7) is a peroxidase enzyme secreted from mammary, salivary, tears and other mucosal glands including the lungs, bronchii and nose[5] that function as a natural, first line of defense against bacteria and viral agents.

The oxidized products display potent, non-specific bactericidal and antiviral activities, including destruction of the influenza virus.

[10] 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.

[15][16] LPO may contribute to the initiation of breast cancer, through its ability to oxidize estrogenic hormones producing free radical intermediates.

[19] Lactoperoxidase catalyzes the hydrogen peroxide (H2O2) oxidation of several acceptor molecules:[20] Specific examples include: Depending on conditions the turnovers with SCN− or I− are roughly similar.

[33] Activation of the lactoperoxidase system by addition of hydrogen peroxide and thiocyanate extends the shelf life of refrigerated raw milk.

[48][49] Thiocyanate secretion[50] in cystic fibrosis patients is decreased, resulting in a reduced production of the antimicrobial hypothiocyanite and consequently contributes to increased risk of airway infection.

[54] Both the hypothiocyanite and the hypoiodate ion products are very potent and importantly non-specific antiviral oxidants which are lethal, even in small concentrations, to the influenza virus.

[57] The duox2-lactoperoxidase system has been shown to offer protection against many dozens of bacteria and mycoplasmas including varieties of the clinically important Staphylococcus and many Streptococcus types.

[58] The lactoperoxidase system efficiently inhibits the common helicobacter pylori in buffer; however, in whole human saliva, it seems to have a weaker effect against this microbe.

[15][17] The ability of lactoperoxidase to propagate a chain reaction leading to oxygen consumption and intracellular hydrogen peroxide accumulation could explain the hydroxyl radical-induced DNA base lesions recently reported in female breast cancer tissue.

[15] Lactoperoxidase may be involved in breast carcinogenesis, because of its ability to interact with estrogenic hormones and oxidise them through two one-electron reaction steps.

After showing indirectly, by means of measuring experimental gingivitis and caries parameters, that mouth rinses[63][64] containing amyloglucosidase (γ-amylase) and glucose oxidase activate the lactoperoxidase system, the protective mechanism of the enzymes in oral care products has been partially elucidated.

[65][66] Also, as part of tooth pastes, the lactoperoxidase system has a beneficial influence to avoid early childhood caries[67] by reducing the number of colonies formed by the cariogenic microflora while increasing the thiocyanate concentration.