SALIVARY AMYLASE PROMOTES ADHESION OF ORAL STREPTOCOCCI TO HYDROXYAPATITE

Recent studies have demonstrated that several species of oral streptoc occi, such as Streptococcus gordonii, bind soluble salivary alpha-amyl ase. The goal of the present study was to determine if amylase immobil ized onto a surface such as hydroxyapatite can serve as an adhesion re ceptor for S. gordonii. Initially, human parotid saliva was fractionat ed on Bio-Gel P60, and fractions were screened for their ability to pr omote adhesion of S. gordonii to hydroxyapatite. Fractions containing alpha-amylase and proline-rich proteins promoted the adhesion of [H-3] -labeled S. gordonii to hydroxyapatite. Similar findings were obtained with purified amylase and acidic proline-rich protein 1 (PRP1). Incub ation of S. gordonii G9B in the presence of starch and maltotriose inc reased the binding of this strain to amylase-coated hydroxyapatite, wh ile the adhesion of S. sanguis 10556 to amylase-coated hydroxyapatite was not affected by these saccharides. These results suggest that amyl ase may serve as a hydroxyapatite pellicle receptor for amylase-bindin g streptococci. Furthermore, starch and starch metabolites may enhance the adhesion of amylase-binding streptococci to amylase in dental pel licles to augment the formation of dental plaque.