New in vitro model for the acquired enamel pellicle: Pellicles formed fromwhole saliva show inter-subject consistency in protein composition and proteolytic fragmentation patterns

The present investigation was undertaken to investigate the variability of proteins in whole saliva which adsorb to hydroxyapatite and are thus likely to be precursors of the acquired enamel pellicle. Whole-saliva proteins fr om 18 subjects were absorbed to hydroxyapatite, and the gel filtration patt erns of released proteins revealed four major peaks and three minor peaks e luting between the major peaks. Amino acid analysis indicated that minor pe aks contained fragments of proteins in major peaks, and this was confirmed by sequence analysis. Major peaks comprised 95% and minor peaks comprised 5 % of protein absorbed to hydroxyapatite, suggesting a limited proteolytic c apacity of whole saliva. HPLC elution patterns of components in minor peaks suggested that proteolysis is not totally random but is an orderly and con sistent process. These studies suggest that whole saliva may be suitable as a model system for the investigation of post-secretory modifications of sa livary proteins important for the formation of the acquired enamel pellicle .