Variation in Bitterness Potency When Introducing Gly-Gly Residue into Bitter Peptides

We previously reported that Gly-Gly-Arg-Pro and Arg-Pro-Gly-Gly, the derivatives of a bitter peptide Arg-Pro, had no bitterness although Gly-Arg-Pro and Arg-Pro-Gly had a bitter taste at the same level as that of Arg-Pro. To elucidate the mechanism of elimination of bitterness by the introduction of the Gly-Gly residues, we synthesized Gly-Gly derivatives of other bitter peptides such as Phe-Phe, Val-Val-Val, and Arg-Pro-Phe-Phe, and examined the effectiveness of Gly-Gly residues in eliminating bitterness. We suggest that, for Arg-Pro and Val-Val-Val, the Gly-Gly residue might prevent a hydrophobic group from binding to a taste receptor.