Multiple forms of dextranase were detected in both intra-and extracellular fractions of
Bacteroides oralis Ig4a. The molecular weights of these enzymes varied from 52,000 to 260,000 by sodium dodecyl sulfate-polyacrylamide-blue dextran gel electrophoresis. The intracellular dextranases were fractionated by chromatography and gel filtration steps, and the dextranases IV and V were obtained. The former was only partially pure. The molecular weights of the dextranases IV and V were estimated to be 120,000 and 105,000, respectively, by SDS-PAGE. The dextranase V was further characterized and it was revealed that the pH-and temperature optima were 5.0, and 55°C, respectively. The Km value was 6.7×10
-2 mM for dextran T-70. The enzyme did not exhibit any metal ion requirements, but was inhibited by CoCl
2 and HgCl
2; lysine and alanine contents were especially high; it hydrolyzed the α-1, 6-glucan by an exo-type mechanism, and was inactive toward glucans containing α-1, 3-, α-1, 4-, and β-1, 4-linkages
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