Development of new method for the diagnosis and treatment of halitosis on several odor-causing agents

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Halitosis originates from microbial putrefaction within the oral cavity, and volatile sulfur compounds (VSCs) are considered the major gases associated with halitosis. In this study, several etiological substances which cause halitosis were examined to develop the new method for the diagnosis and treatment of halitosis.At first, the applicability of ammonia monitoring for assessing halitosis was examined. There was a significant correlation between ammonia level and the total VSC level measured with gas chromatography. Significant correlations were also observed between ammonia level and levels of methyl mercaptan produced by bacteria in dental plaque and tongue coating. Furthermore, the ammonia level decreased after the removal of tongue coating and dental plaque. These results indicate that measuring ammonia levels is useful for assessing halitosis, specifically for halitosis arising from a lack of oral hygiene.Next, the enzyme that produces hydrogen sulfide from L-cysteine was purified from Streptococcus anginosus. The led gene encoding L-cysteine desulfhydrase was cloned, and then the recombinant protein was purified to examine its enzymatic and biological characteristics. This L-cysteine desulfhydrase had the following Michaelis-Menten kinetics: K_m = 0.62 mM and V_<max> = 163 μmol min^<-1> mg^<-1>. In addition, we demonstrated that the hydrogen sulfide produced by this enzyme caused the modification and release of hemoglobin in sheep erythrocytes. These results indicate that the inhibition of this enzyme is important not only for the decrease of oral malodor but also for the protection of oral tissues from the toxicity of hydrogen sulfide.