Characterization of a dextranase produced by an oral strain of Actinomyces israelii

Abstract

A dextranase-producing, gram-positive, anaerobic, rod-shaped bacterium isolated from human dental plaque was identified as Actinomyces israelii. Although the extracellular dextranase (EC 3.2.1.11) formed by this microbe appeared to be constitutively produced, the bacterium did not utilize the reaction products as a carbon source during growth. A striking feature of the dextranase was the formation of two distinct groups of oligosaccharide end products. The two groups presumably correspond to the limit dextran and the released reaction product which appeared to be cleaved from the end(s) of larger dextran molecules. Low levels of dextranase activity were measured by [3H ]NaBH4 reduction and alcohol fixation of the large, tritiated end products on filter paper disks. Of the carbohydrate substrates tested, only a-1,6-linked glucans were cleaved. The enzyme did not exhibit any metal ion requirements, and its pH optimum was 6.3. It is suggested that the A. israelii dextranase may function as a regulatory factor during extracellular in vivo glucan synthesis from sucrose by various plaque microbes.

Extracellular dextranase activity produced by human oral strains of the genus Bifidobacterium

“…though several genera can elicit dextranase acbacteria convert fructose-6-phosphate tivity, not all of these strains can use the tyl phosphate and erythrose-4-phos-degradation products of dextran hydrolysis as ith the enzyme fructose-6-phosphate growth substrates; for example, A. israelii and ketolase (6). S. mutans cannot (29). Bacteroides ochraceus, gh strain MLBI-3 produced acetate and on the other hand, can utilize its degradation lose to the theoretical acetate-lactate products for growth (30).…”

“…Dextranase-producing microorganisms appear to be ubiquitous in samples of dental plaque (15,27). Oral bacteria capable of demonstrating this type of enzymatic activity include many of the streptococci (7,28,32), Fusobacterium fusiforme (5), Actinomyces israelii (29), and Bacteroides ochraceus (30). The different dextranases produced by these bacteria vary in such properties as cell-bound versus extracellular production, exohydrolytic versus endohydrolytic mode of degradation, and pH optimum.…”

Label-Free High-Throughput Functional Lytic Assays

“…Protein substrates used for the substrate-specific digestion analysis were human serum albumin (HSA; Sigma Aldrich, A3782), methylated bovine serum albumin (BSA; Sigma Aldrich, A1009), BSA fraction V (Sigma Aldrich, A-3059), acetylated BSA (Gibco-BRL, Grand Island, NY; 15561-020), and carbonic anhydrase II (EC 4. 22…”

“…Metal ions such as mercury and silver have been reported as effective inhibitors of dextranase. 22 Normally, the measurement of direct binding of ion inhibitors to immobilized enzymes would not be detectable on an evanescent biosensor because their mass is below current detection capabilities.…”

Removing Dental Plaque Biofilm: A Review of Dextranases

“…Dextranase has represented excellent effect value in the prevention and removal of dental plaque biofilm [26][27][28][29][30][31][32][33][34][35]&[Table 2]. As early as 1971, Caldwell and Robert conducted related studies on adding dextranase to mouthwashes to treat dental plaque biofilm [36].…”