Studies concerning the glucosyl-transferase of Streptococcus sanguis

We have shown in previous studies that the glucosyltransferase (Gtf) enzyme s of Streptococcus mutans have distinct properties when adsorbed to a surfa ce. In the present study, we compared the activity of Gtf from Streptococcu s sanguis, designated GtfSs, in solution and on the surface of saliva-coate d hydroxyapatite (sHA) beads, and determined the ability of its product glu can to support the adherence of oral microorganisms, Gtf from S. sanguis 80 4 NCTC 10904 was purified from culture supernatant fluids by mea ns of hydr oxyapatite chromatography, Enzyme and the substrate were prepared in buffer s at pH values from 3.5 to 7.5. Maximum activity of GtfSs occurred between pH 5.5 and pH 6.5, whether in solution or adsorbed onto a surface. The solu bilized and insolubilized enzymes showed highest activity at 40 degrees C; activity was reduced by 50(+/-2)% at 20 and 30 degrees C, The enzyme did no t form glucans in either phase at 10 or 60 degrees C, The K-m, determined f rom Lineweaver-Burk plots, for the enzyme in solution was 4.3(+/-0.4) mmol/ l sucrose, and the K-m for the enzyme on sHA beads was 5.0(+/-1.0) mmol/l s ucrose. The ability of the GtfSs glucan synthesized on the surface of sHA b eads to support the adherence of oral bacteria was investigated. H-3-thymid ine-labeled bacteria (S. mutans GS-5, S. sobrinus 6715, S, sobrinus 6716, S , sanguis 10904, Actinomyces viscosus OMZ105E, A. viscosus 2085, and A. vis cosus 2086) were incubated with sHA beads coated with GtfSs glucan, S. muta ns GS-5 displayed the highest level of binding numerically. These results s how that the GtfSs of S. sanguis is active on sHA beads, that the pH optimu m for activity on a surface differs slightly from that in solution, and tha t its product glucan can support the adherence of oral microorganisms, Copy right (C) 1999 S. Karger AG. Basel.