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

口臭源于口腔内的微生物腐败，挥发性硫化合物（VSC）被认为是与口臭相关的主要气体。本研究通过对引起口臭的几种致病物质的检测，为口臭的诊断和治疗提供新的方法。氨水平与气相色谱法测定的总VSC水平之间存在显著相关性。牙菌斑和舌苔中细菌产生的甲基苯丙胺水平与氨水平也存在显著相关性。此外，去除舌苔和牙菌斑后，氨水平降低。这些结果表明，测量氨水平对于评估口臭是有用的，特别是对于缺乏口腔卫生引起的口臭。接下来，从咽峡炎链球菌中纯化了从L-半胱氨酸产生硫化氢的酶。克隆了L-半胱氨酸脱氢酶的编码基因，并对重组蛋白进行纯化，研究其酶学性质和生物学特性。该酶具有米氏动力学：K_m = 0.62 mM，V_m <max>= 163 μmol·min ~（-1）·<-1>mg ~（-1）<-1>。此外，我们证明了这种酶产生的硫化氢引起绵羊红细胞中血红蛋白的修饰和释放。这些结果表明，这种酶的抑制不仅对减少口腔恶臭，而且对保护口腔组织免受硫化氢的毒性是重要的。

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.