Insoluble Glucan Degrading Activity of Bacteroides Isolated from Human Dental Plaque

Glucan hydrolyzing activities of Bacteroides oralis, isolated from human dental plaque, and Bacteroides fragilis, isolated from rat dental plaque, were studied. Crude enzymes were obtained by salting out with 60% saturation of ammonium sulfate from the culture of B. oralis and B. fragilis respectively. The activities were determined by using of commerical dextran T-2, 000 (Pharmacia, M. W. 2, 000, 000) (SG), insoluble glucan produced by Streptococcus mutans FA-1 (IsG) and partially Smith degraded IsG (M-IsG) which contained α- (1-3) bond in most proportion of linkage. Commercial dextranase from Penicillium spp. (Worthington) was used as control. Commercial dextranase degraded SG almost completely, but showed weak or no activity to IsG and M-IsG. It was natural for the enzyme which was α- (1-6) glucanase. The enzymes of B. fragilis showed similar activity to the 3 kinds of glucan. They were active against SG, but less active against IsG or M-IsG. On the other hand, enzymes isolated from B. oralis degraded IsG and M-IsG as well as SG. This was also detected on thin layer chromatography. These results indicated that B. oralis produced the enzymes hydrolyzing each of α- (1-3) linkage and α- (1-6) linkage of glucan produced by S. mutans.