Characterization of water-insoluble polyglucan hydrolase from Streptomyces species

Abstract

Water-insoluble polysaccharides produced from sucrose by cariogenic streptococci are one of the constitutive components of dental plaque matrix and play a decisive role in dental plaque formation which may result in the development of dental caries and marginal periodontal diseases. It has been reported in our laboratory that two strains of soil microorganisms identified as Streptomyces werraensis and Streptomyces chartreusis are isolated from soils, which grow well with clear translucent zones around their colonies on the agar containing the water-insoluble polysaccharides from cariogenic streptococci. The present reports describes the characterizations of the water-insoluble polysaccharides hydrolysing enzyme extracellulary produced by the strains.Chemical analyses on purified preparations of water-insoluble polysaccharides obtained from Streptococcus mutans strain AHT, HS-6, BHT, FA-1, Ingbritt, OMZ 70, K 1-R and OMZ 176 and Streptococcus salivarius strain HHT revealed that they were composed of only glucose but n fractose and that more than 50% of their glycosidic linkages were (1→3)-bonds and the remaining ones were (1→6) or (1→2/1→4). A preparation of dextranase commercially availed was shown to hydrolyze rather to a limited extent the insoluble polysaccharides. To the contrary, both waterinsoluble polyglucanases termed F1 and F2 enzyme from S. werraensis and S. chartreusis respectively, were strongly hydrolyzed the water-insoluble polyglucans from all streptococcal strains tested. They could also hydrolyze the periodate-oxidized and borohydride-reduced polyglucans, but were inert against 10 saccarides which have already been known to contain α-or β-anomers of 1→6, 1→2 and 1→4 glycosidic linkages. These results indicated that both F1 and F2 enzyme cleaved 1→3 glycosidic linkage of the water-insoluble polygucans. Some properties of crude preparations of the polyglucanases were examined.