The salivary peroxidase system: thermodynamic, kinetic and antibacterial properties.

Enzymes are specific catalysts which optimize the rates of reactions vital to living organisms. If the oxidation of thiocyanate (which occurs, in vivo, in human saliva and salivary glands) is a vital reaction for the maintenance of oral health, then the enzyme (salivary peroxidase), which catalyzes this reaction, should function optimally under in vivo conditions. Studies have shown that salivary peroxidase maintains the SCN- oxidation reaction in an apparent state of dynamic equilibrium, that the kinetic properties of the enzyme provide optimum rates of reaction under in vivo conditions, and that the antibacterial properties of the products of the reaction are optimum under those conditions where unlimited bacterial metabolism provides the greatest threat to host tissues. The evidence indicates that the salivary peroxidase enzyme has evolved in such a way as to maximize its protective value in the oral cavity.