Studies of Bitter Peptides from Casein Hydrolyzate. VI. Syntheses and Bitter Taste of BPIc (Val–Tyr–Pro–Phe–Pro–Pro–Gly–Ile–Asn–His) and Its Analogs and Fragments

Abstract

Abstract In order to investigate the relationship between chemical structure and bitter taste, the bitter peptide BPIc (Val–Tyr–Pro–Phe–Pro–Pro–Gly–Ile–Asn–His) isolated from casein hydrolyzate by Minamiura et al. and its analogs and fragments were synthesized. BPIc, whose threshold value of bitter taste was 0.05 mM, was found to be one of the most bitter compounds, like quinine and phenylthiourea. However, [Gly5,6]- and [Gly9,10]-BPIc, and N-terminal octa- and heptapeptide fragments of BPIc possessed much weaker bitterness than BPIc. The results suggested that 5,6-proline and the basic nature of C-terminal are necessary for the strong bitterness exhibited by BPIc.