Nattokinase, a Subtilisin-like Alkaline-Serine Protease, Reduces Mutacin Activity by Inactivating the Competence-Stimulating Peptide in Streptococcus mutans

is a major cariogenic organism because of its ability to form biofilms on tooth surfaces. Bacteriocins produced by (known as mutacins) are indirect pathogenic factors that play a role in the persistence of this microbe in the oral environment. Nattokinase, a subtilisin-like alkaline serine protease, potently inhibits biofilm formation without affecting growth. However, effective strategies utilizing nattokinase to control mutacin production by are lacking. In this study, we evaluated the effect of nattokinase on mutacin activity in 46 strains of with different mutacin genotypes isolated from the dental plaques of pediatric patients with caries. Nattokinase reduced the activity of mutacin against oral streptococci at a concentration of 1 mg/mL in all clinical isolates. Furthermore, nattokinase reduced the expression of non-lantibiotic mutacin structural genes ( ) and inactivated the extracellular competence-stimulating peptide involved in activation, which regulates non-lantibiotic mutacin gene expression. These results suggest that nattokinase may reduce the virulence of and could potentially be used as a new caries-preventive agent as an alternative to conventional drug treatments.