BINDING-PROPERTIES OF STREPTOCOCCAL GLUCOSYLTRANSFERASES FOR HYDROXYAPATITE, SALIVA-COATED HYDROXYAPATITE, AND BACTERIAL SURFACES

The binding specificities of Streptococcus glucosyltransferase (Gtf) B , C and D for hydroxyapatite (HA), saliva-coated hydroxyapatite (SHA), and bacterial surfaces were examined. For HA beads the following valu es were obtained: (K = affinity; N = number of binding sites) GtfB, K = 46 x 10(5) ml/mu mol, N = 0.65 x 10(-6) mu mol/m(2); GtfC, K = 86 x 10(5) ml/mu mol, N = 4.42 x 10(-6) mu mol/m(2); GtfD, K = 100 x 10(5) ml/mu mol, N = 0.83 x 10(-6) mu mol/m(2). For SHA beads, the following values were obtained: GtfB, K = 14.7 x 10(5) ml/mu mol, N = 1.03 x 10 (-6) mu mol/m(2); GtfC, K = 21.3 x 10(5) ml/mu mol, N = 3.66 x 10(-6) mu mol/m(2); GtfD, K = 1.73 x 10(5) ml/mu mol, N = 8.88 x 10(-6) mu mo l/m(2). The binding of GtfB to SHA beads was reduced in the presence o f parotid saliva, but the binding of GtfC and D was unaffected. The bi nding of GtfB to SHA in the presence of parotid saliva supplemented wi th GtfC and D was reduced when compared with its binding to SHA in the presence of parotid saliva alone. In contrast, the binding of GtfC an d D to SHA was unaffected when parotid saliva was supplemented with th e other Gtf enzymes. GtfB bound to several bacterial strains (Strep. m utans GS-5, Actinomyces viscosus OMZ105E and Lactobacillus casei 4646) in an active form, while GtfC and D did not bind to bacterial surface s. It is concluded that of the three Gtf enzymes, GtfC has the highest affinity for HA and SHA surfaces and can adsorb on to the SHA surface in the presence of the other two enzymes. GtfD also binds to SHA in t he presence of the other enzymes but has a very low affinity for the s urface. GtfB does not bind to SHA in the presence of the other Gtf enz ymes but binds avidly to bacterial surfaces in an active form. Therefo re, GtfC most probably binds to apatitic surfaces, while GtfB binds to bacterial surfaces. (C) 1998 Elsevier Science Ltd. All rights reserve d.