Study on the pathogenicity of halitosis-causing agents and development of new method for the treatment

βC-S裂解酶催化L-半胱氨酸的α，β-消除为硫化氢，硫化氢是口腔恶臭的主要原因之一，对哺乳动物细胞具有高度毒性。我们评估了六种口腔链球菌产生硫化氢的能力。其中咽峡炎链球菌粗提物的产酶能力最强。然而，氨基酸序列的比较分析未检测到咽峡炎链球菌βC-S裂解酶的任何有意义的差异。咽峡炎链球菌纯化的βC-S裂解酶降解L-半胱氨酸的能力也非常高，而其降解L-胱硫醚的能力不显著。从咽峡炎链球菌中克隆了一个编码胱硫醚γ-合酶的基因（cgs），并对其蛋白进行了纯化和鉴定。cgs基因和直接下游的lcd基因被证明是作为一个操纵子共转录。HPLC分析表明，咽峡炎链霉菌Cgs不仅具有胱硫醚γ-合成酶活性，而且表达O-乙酰高丝氨酸硫化氢解酶活性。这些结果表明，S.anginosus有能力利用转硫和直接巯基化途径为homocysteine biosynthesis.We研究了天然牙菌斑在小鼠中的致龋诱导能力，由菌斑产生的感染位点的微生物特征，以及微生物分离株的抗吞噬特性。在大多数小鼠中使用不同的斑块样品诱导脓肿形成。脓液的微生物组成与诱发脓肿的菌斑样本相比非常简单。大多数分离株属于咽峡炎链球菌组，通常是菌斑样本的次要组分。这些结果提示咽峡炎链球菌的致病性与其产生大量硫化氢的能力有关。

βC-S Lyase catalyzes the α,β-elimination of L-cysteine to hydrogen sulfide, which is one of the main causes of oral malodor and is highly toxic to mammalian cells. We evaluated the capacity of six species of oral streptococci to produce hydrogen sulfide. The crude enzyme extract from S.anginosus had the greatest capacity. However, comparative analysis of amino acid sequences did not detect any meaningful differences in the S.anginosus βC-S lyase. The capacity of S.anginosus purified βC-S lyase to degrade L-cysteine was also extremely high, while its capacity to degrade L-cystathionine was unremarkable. These findings suggest that the extremely high capacity of S.anginosus to produce hydrogen sulfide is due to the unique characteristic of βC-S lyase from that organism.A gene (cgs) encoding cystathionine γ-synthase was cloned from Streptococcus anginosus, and its protein was purified and characterized. The cgs gene and the immediately downstream lcd gene were shown to be cotranscribed as an operon. HPLC analyses showed that the S.anginosus Cgs not only has cystathionine γ-synthase activity, but also expresses O-acetylhomoserine sulfhydrylase activity. These results suggest that S.anginosus has the capacity to utilize both the transsulfuration and direct sulfhydrylation pathways for homocysteine biosynthesis.We examined the abscess-inducing ability of native dental plaque in mice, the microbial features of the infectious locus produced by the plaque, and the anti-phagocytic property of microbial isolates. Abscess formation was induced in most mice using different plaque samples. The microbial composition of pus was very simple compared to that of the plaque sample that had induced the abscess. The majority of the isolates belonged to the S.anginosus group, normally a minor component of plaque samples. These results suggest that the pathogenicity of S.anginosus is related to its ability to produce hydrogen sulfide at high level.