Studies of Bitter Peptides from Casein Hydrolyzate. X. Synthesis and Bitter Taste of H–Arg–Gly–Pro–Phe–Pro–Ile–Ile–Val–OH Corresponding to C-Terminal Portion of β-Casein

Abstract

In order to ascertain the validity of the structure of bitter peptide BPIa (H–Arg–Gly–Pro–Pro–Phe–Ile–Val–OH) isolated from casein hydrolyzate by Minamiura et al., the C-terminal octapeptide of β-casein (H–Arg–Gly–Pro–Phe–Pro–Ile–Ile–Val–OH) determined by Ribadeau Dumas et al., which is assumed to correspond to BPIa, was synthesized and compared with the synthetic BPIa which was confirmed to be identical with the natural one. The two synthesized peptides, however, did not match on thin-layer chromatography. The result indicates that the structure of BPIa need not be converted to Ribadeau Dumas’ formula. The octapeptide possessed an extremely bitter taste, with a threshold value of 0.004 mM (1 M=l mol dm−3). It is the most bitter peptide.

Specificity of Carboxypeptidases from Actinomucor elegans and Their Debittering Effect on Soybean Protein Hydrolysates

“…The bitterness is usually associated with peptides with a high content of hydrophobic amino acids [4], and becomes stronger as the content of hydrophobic amino acids increases or becomes more concentrated at the C terminus [5][6][7][8][9]. It was reported that the bitterness of the oligopeptide Arg-Pro-Phe-Phe, which has a hydrophobic Phe-Phe at the C terminus, was 25 times greater than that of caffeine.…”

Bitter Taste of H-Pro-Phe-Pro-Gly-Pro-Ile-Pro-OH Corresponding to the Partial Sequence (Positions 61 ~ 67) of Bovineβ-Casein, and Related Peptides

“…20 and 22 were condensed by the DCC method to yield Boc-Pro-Phe-Pro-Gly-Pro-Ile-Pro-OBzI (23). This protected heptapeptide was hydrogenated in the presence of palladium black and then the resulting acid (24) was treated with hydrogen chloride in formic acid to yield the desired product (1).…”

Bitter Taste of Synthetic C-Terminal Tetradecapeptide of Bovine β-Casein, H-Pro196-Val-Leu-Gly-Pro-Val-Arg-Gly-Pro-Phe-Pro-Ile-Ile-Val209-OH, and Its Related Peptides

“…The Boc group was removed from the intermediates by hydrogen chloride in dioxane and the benzyl ester was removed by catalytic hydrogenation or saponification. The protected octapeptide (37) (38) was hydrogenated in the presence of palladium black to yield the desired peptide (9). The synthetic routes to other peptides (10 and 11) are shown in Figs.…”

“…7b. It is suggested that the spatial structure of 3 is not kept in its retro form (9), therefore, 9 was not as bitter as 3. Further, we consider that the structure of 9 may prevent its C-terminal arginine residue from contributing to the increase ofbltterness, by adding the results of the sensory test to that of CD measurements.…”