Biologically active substances produced by Bacteroides gingivalis and their periodontopathogenicity

牙龈类杆菌产生几种生物活性物质。本研究的目的是从牙周组织培养上清液中分离纯化出与牙周组织致病性和细胞毒性相关的蛋白酶、血凝素和组织细胞凝集素等物质。血凝素被认为参与细菌对宿主组织的黏附。该HA的红细胞受体蛋白为带3蛋白，其精氨酸残基与其结合有关。该透明质酸既具有类胰酶活性，又具有组织细胞聚集活性，可能是类胰酶与带3蛋白发生酶-底物反应的结果。牙龈假单胞菌产生的类胰酶具有水解I型胶原、Ig G、Ig A等天然蛋白的能力。该酶对人牙龈成纤维细胞也有较强的细胞毒作用。这些事实表明，该酶不仅通过直接破坏牙周组织，而且通过降低宿主的免疫防御能力而具有致病性。所有这些生物活性物质都集中在牙龈假单胞菌分泌的外膜囊泡中，并且它们在几种蛋白酶抑制剂上的作用方式都是相同的。这些结果表明，牙龈假单胞菌致病因子的真实特征可能是与外膜小泡结合的类胰蛋白酶。

Bacteroides gingivalis produces several types of biologically active substances. The purpose of this investigation is to determine the properties of these substances such as proteases, hemagglutinin and tissue-cell agglutinating factor etc. in association with periodontopathogenicity and cytotoxicity.Hemagglutinin (HA), which is considered to participate in the bacterial adherence to host tissues, was isolated and purified from the culture supernatant. The receptor protein of the erythrocyte for this HA was clarified to be band 3 protein and the arginine residue of the peptide was concerned in the binding. This HA possessed both the trypsin-like and the tissue-cell aggregating activities, suggesting that hemagglutination may occur as a result of enzyme-substrate reaction between the trypsin-like enzyme and the band 3 protein.The trypsin-like enzyme produced by B.gingivalis showed the ability of hydrolyzing type I collagen, IgG, IgA and some other naturally occurring proteins. This enzyme also had strong cytotoxicity on human gingival fibroblasts. These facts indicate that the enzyme exhibits pathogenicity not only by destroying periodontal tissue directly but also by decreasing host immune defense ability.All these biologically active substances are concentrated in the secreted outer membrane vesicles of B.gingivalis and all of them behaved in the same way on several protease inhibitors. These results suggest that the true feature of the pathogenic factor of B.gingivalis could be the trypsin-like protease which associates with the outer membrane vesicles.