Twenty strains of anaerobic "bacteria including some oral species from Bacteroides, Eikenelia, Eusobacterium, Capnocytophaga, and Actinobacillus were used for the detection of collagenolytic activity in their culture media (supernatants). Organisms were essentially grown in complete anaerobic basal broth, and coliagenolytic activities in the culture media were measured using '^C-acetylated soluble collagen from rat skin. When the enzyme reaction was carried out in the standard reaction mixture for 60 min, very low collagenolytic activities were found in culture media of Bacteroides gingivalis 381, 1021, Bacteroides intermedius 163, Kl-8, Bacteroides asaccharolyticus ATCC 27067, and Eusobacterium nucteatum ATCC 25586. However, the activity in the media of all species of B. gingivalis tested was enormously enhanced by the addition of reducing reagents having thiol-groups such as dithiothreitol, L-cysteine, etc. This stimulated activity was nearly completely inhibited by some thiol-blocking reagents. In contrast, these reagents had no effect on the collagenolytic activity in the media of the other anaerobes and in the coUagenase preparation of Clostridium histolyticum. These results suggest that B. gingivalis produces thiol-dependent collagenolytic enzyme which may play an important role in the degradation of coilagen fibrils in a reduced environment like the deep gingival pocket.

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Significant positive correlations between protease activities in saliva and supragingival/subgingival calculus indices, periodontal pocket depth, or P-M-A index were confirmed. When the partial correlation was calculated, the subgingival calculus index correlated well with the sediment protease at pH 8.5, and the supragingival calculus index showed a significant correlation with the supernate protease at pH 4.5.

Neuraminidase acting on the salivary bacterial agglutinating factor was isolated and purified from the culture medium of Streptococcus mitis ATCC 9811. The molecular weight and the isoelectric point of the enzyme were determined to be 42,000 and a pH of 4.6, respectively. The enzyme showed high activity against human glycoprotein substrates, especially the salivary bacterial agglutinating factor.