人唾液過酸化酵素抗菌系による Cariogenic Streptococcus の有機酸生成阻害に関する研究

抄録

Antibacterial action of human saliva has been one of the central subjects in oral biology and numerous studies have been reported. Among antibacterial factors possibly present in human saliva, lysozyme and an anti-lactobacillus factor are the ones that have received most extensive studies. In recent years, the nature of this anti-lactobacillus factor requiring thiocyanate as a cofactor for its activity became clarified and proved to be a salivary peroxidase. Subsequent studies have established that the salivary peroxidase (SPO) antibacterial system consisted of three integral components, that is, salivary peroxidase, hydrogen peroxide and thiocyanate. Although the mode of action of the SPO antibacterial system has now been largely clarified, the physiological significance of such system in the oral cavity remains obscure. The purpose of this experiment is to study the role of the SPO system in inhibiting the acid production by a strain of caries-conducive streptococcus (strain BHT). The assay organism produced organic acids extracellularly from carbon-labelled glucose and sucrose in 0.05 M phosphate buffer, pH 5.8, and two kinds of acids were demonstrated by column chromatography with Dowex 1, x 8 formate resin, and these acids were respectively identified as lactate and pyruvate by partition chromatography with silica gel, of which lactate was revealed to be the main product of acids that were excreted by the organism. The production of lactate and pyruvate was inhibited to the extent of 96 per cent on 60-minute incubation with SPO antibacterial system. Similar inhibition was obtained from the experiment with SPO antibacterial system, in which the salivary peroxidase (partialy purified preparation) was replaced by human whole saliva containing a sufficient amount of peroxidase. The inhibition of acid production took place with no apparent decrease in the cell number of viable organism. The experimental results in vitro would contribute to subsequent in vivo studies for the prevention of experimental caries in animal by the SPO antibacterial system.