Human Salivary Peroxidase and Bovine Lactoperoxidase are Cross-reactive

Abstract

Peroxidases are abundant in nature, and the primary function of mammalian peroxidases is to catalyze the peroxidation of halides and pseudohalides. Previous studies have shown that antibodies raised against bovine lactoperoxidase moderately cross-react with human salivary peroxidase, a feature that has been used in the present study to examine epitopes common to the antigen and human salivary peroxidase. Polyclonal antibodies against a highly purified preparation of bovine lactoperoxidase were raised in rabbits, and their properties were examined. In double-immunodiffusion experiments, the two enzymes showed partial identity, and in competitive radioimmunoassay and enzyme-linked immunosorbent assay, lactoperoxidase replaced the labeled and coated antigen, while salivary peroxidase did not. However, salivary peroxidase from human and rat saliva samples and the purified enzyme in its non-reduced, reduced, and de-glycosylated forms were recognized by these antibodies, as analyzed by Western blot analysis and immunodetection. The major activity of these antibodies was directed against the protein core of the antigen. Immunodetection of the peptide fragments of bovine lactoperoxidase and human salivary peroxidase revealed structural differences in the two enzymes. These antibodies also precipitated an in vitro translation product from rat-parotid-gland cell lysate that, on SDS-PAGE, compared favorably with the expected molecular weight of a de-glycosylated peroxidase. The antibodies partly inhibited the enzyme activity of salivary peroxidase and the peroxidase in rat parotid gland lysate, but the enzyme activity of lactoperoxidase was not affected by addition of anti-lactoperoxidase IgG between 25 and 400 micrograms/mL. The enzyme activity remained unchanged in all samples when pre-immune IgG was used.

Effect of lactoperoxidase on the antimicrobial effectiveness of the thiocyanate hydrogen peroxide combination in a quantitative suspension test

“…Human SPO is slightly different from industrially produced LPO. However, the main characteristics of the industrially produced LPO are identical to saliva peroxidase [16,17]. Based on this similarity, industrially produced LPO is used instead of SPO in studies and is often referred to as LPO in the literature [37].…”

“…The complete peroxidase system in saliva comprises three components: the peroxidase enzymes (glycoprotein enzyme), salivary peroxidase (SPO) from major salivary glands and myeloperoxidase (MPO) from polymorphonuclear leucocytes filtering into saliva from gingival crevicular fluid; hydrogen peroxide (H 2 O 2 ); and an oxidizable substrate such as the pseudohalide thiocyanate (SCN - ) from physiological sources [14,15]. SPO is almost identical to the milk enzyme lactoperoxidase (LPO) [16,17]. All these peroxidase enzymes catalyze the oxidation of the salivary thiocyanate ion (SCN - ) by hydrogen peroxide (H 2 O 2 ) to OSCN - and the corresponding acid hypothiocyanous acid (HOSCN), O 2 SCN - , and possibly O 3 SCN - [18], which have been shown to inhibit bacterial [19-23], fungal [24], and viral viability [25].…”

The Dual Role of Saliva in Oral Carcinogenesis

“…Other detectable salivary enzymes, such as catalase, glutathione peroxidase and glutathione reductase, have only marginal antioxidant significance [34]. Two peroxidase enzymes are found in saliva: salivary peroxidase, which in structure and antigenic characteristics resembles the lactoperoxidase found in bovine milk [26, 35, 36], and myeloperoxidase, produced by leukocytes in inflammatory regions of the oral cavity [37, 38]. Despite the importance of peroxidase in saliva, it accounts for only 0.01% of the total salivary protein and exists in equilibrium between a monomeric state and multimolecular aggregates [26, 36, 39].…”

“…The salivary peroxidase secreted from the major salivary glands, mainly the parotid gland [27], contributes 80% of OPO activity, while myeloperoxidase, produced by leukocytes in inflammatory regions of the oral cavity [37], contributes the remaining 20% of OPO activity. In structural and antigenic characteristics, salivary peroxidase resembles the lactoperoxidase found in bovine milk [26, 35]. OPO plays a dual role: (1) it reduces the level of hydrogen peroxide (H 2 O 2 ) excreted into the oral cavity from the salivary glands by bacteria and by leukocytes, and (2) it increases specific antibacterial activity by inhibiting the metabolism and proliferation of various bacteria in the oral cavity.…”

Lactoperoxidase Inhibits Glucosyltransferases from <i>Streptococcus mutans </i>in vitro

“…Peroxidase-generated HOSCN/OSCNhas several antistreptococcal activities in vitro [Månsson-Rahemtulla et al, 1987;Tenovuo et al, 1988;Roger et al, 1994], which are mainly due to its oxidative capacity. Structurally and catalytically human salivary peroxidase is very similar to bovine lactoperoxidase (LP, EC 1.11.1.7) [Månsson-Rahemtulla et al, 1990], which is widely used in studies on peroxidase-mediated functions. Salivary peroxidase enzyme is found in active form in human dental plaque and pellicle [Pruitt and Adamson, 1977;Tenovuo and Kurkijärvi, 1981].…”