The association of basic proline-rich peptides from human parotid gland secretions with caries experience

To address whether there are associations between the peptide composition o f human parotid saliva and dental decay (caries) experience, we have charac terized the peptides from parotid ductal saliva collected from nine adults who have remained free from dental caries (mean age = 59.2; Decayed Missing Filled Surfaces index [DMFS] = 0) and nine individuals who have experience d caries (mean age = 51.2; mean DMFS = 38.4). Ethanol-soluble peptides were site-fractionated on columns of Bio-Gel P-2; the salivary peptides derived from caries-susceptible subjects appeared larger than those found in the s aliva of caries-free subjects. Peptides were then resolved into 19 species by cation exchange HPLC. Sequence analysis identified 18 peptides that appe ar to be proteolytic cleavage products of the basic proline-rich proteins I B-4, IB-5, IB-7, IB-8b, and P-B. The peptides that were more abundant in sa liva obtained from the caries-free group differed from those isolated from the caries-susceptible group. The median peptide concentration of one possi ble precursor protein, IB-7, was found to be higher in saliva collected fro m caries-free individuals than in that from caries-susceptible individuals. Although differences were found in the phenotypes of proline-rich proteins expressed by these groups of caries-free and caries-susceptible subjects, no statistically significant associations were observed among proline-rich phenotypes and the level of any peptide. Collectively, our results indicate that proteolytic processing of parotid salivary proteins differs among ind ividuals who have remained caries-free and those who have experienced denta l decay.