The genetic predisposition to taste 6-n-propylthiouracil (PROP) varies greatly among individuals and may be correlated with saliva chemical composition. We investigated the possible relationship between PROP bitter taste sensitivity and salivary proteome.

The intensity of taste perception evoked by PROP and NaCl solutions was estimated to evaluate PROP taster status in forty-five volunteers (16 males, 29 females, age 25 ± 3 y). Quantitative and qualitative determination of salivary proteins was performed by HPLC-ESI-MS technique in individuals classified by PROP status before and after PROP taste stimulation.

ANOVA revealed a significant two-way interaction of Taster group ´ Protein type on basal levels of un-stimulated saliva proteins and peptides. Post-hoc comparisons showed that only basal levels of peptide II-2 and Ps-1 protein of bPRPs family was significantly higher in supertaster than in nontaster un-stimulated saliva. Pairwise comparisons subsequent to three-way ANOVA showed that PROP stimulation determined an increase of only peptide II-2 and Ps-1 protein levels of supertaster saliva with respect to the basal levels.

Our results show for the first time that responsiveness to PROP is strongly associated with proteome, and suggest that the II-2 and Ps-1 proteins, as transporters of hydrophobic molecules, could interact and carry the stimulus to receptor sites.