Biological Significance of Salivary Peroxidase (SPO) System

Objectives:For a number of years our research efforts have been concerned with structure, function, and biological properties of the SPO system. The system is composed of the enzyme SPO, the thiocyanate ion (SCN-) and hydrogen peroxide (H2O2). It has a dual function in the oral cavity, generating the antibacterial agent hypothiocyanite anion (OSCN-) and detoxifying H2O2. Methods:We have demonstrated that for oral streptococci this system is bacteriostatic not bacteriocidal. Supplementation of saliva with H2O2 results in effective inhibition of dental plaque acid production. We have presented evidence for synergism between the SPO system and lysozyme, which results in a significant enhancement of inhibition of glucose metabolism by S. mutans. Results:We have presented evidence that the SPO system is in a dynamic equilibrium in vivo and any disturbances of the equilibrium would result in deleterious effect to oral mucosa. For example, leukemia patients undergoing chemotherapy have lower levels of SCN- than do healthy control subjects. These observations imply that treatment with cytotoxic agents results in defects in absorption and secretion of SCN- by salivary glands. Conclusions: Our laboratory was the first to isolate SPO enzyme and chemical, enzymatic and immunological characterization of the enzyme have been performed. Monoclonal and polyclonal antibodies have been produced and characterized. Recent studies from our laboratory have involved molecular cloning and sequence of the SPO.