To explain the bitter taste exhibited by BPIa (Arg–Gly–Pro–Pro–Phe–Ile–Val) which was isolated from casein hydrolyzate, we have proposed the following requirement: its characteristic spatial structure: the basic moiety in the N-terminal and the hydrophobic moiety in the C-terminal were affected to each other by prolylprolyl residue, is necessary for the bitterness to be exhibited. As for BPIc (Val–Tyr–Pro–Phe–Pro–Pro–Gly–Ile–Asn-His), which is the other fraction, although it exhibited as strong and bitter a taste as BPIa, the basic moiety of BPIc is located in the C-terminal and its hydrophobic moiety is located in the N-terminal. The authors synthesized retro-BPIa with the reverse peptide sequence and its fragments. The retro-BPIa exhibited as strong and bitter a taste as BPIa. However, the bitterness of the fragments of retro-BPIa was far weaker than that of retro-BPIa.
为了说明从
酪蛋白水解物中分离出的B
PIa(Arg–Gly–Pro–Pro–Phe–Ile–Val)所表现出的苦味,我们提出了以下要求:其特征空间结构,即N末端的基本部分与C末端的疏
水部分通过脯
氨酸残基相互影响,是表现苦味所必需的。至于另一种成分B
PIc(Val–Tyr–Pro–Phe–Pro–Pro–Gly–Ile–Asn-His),虽然它表现出的味道与B
PIa一样强烈而苦涩,但B
PIc的基本部分位于C末端,疏
水部分位于N末端。作者合成了逆B
PIa,其肽序列相反及其片段。逆B
PIa表现出的苦味同样强烈,但逆B
PIa片段的苦味远弱于逆B
PIa。