Abstract
To estimate the steric distance between the bitter taste determinant sites in peptides, some cyclic dipeptides, amino acid anilides, amino acid cyclohexylamides, and benzoyl amino acids were synthesized and their tastes were evaluated. The diketopiperazine ring of cyclic dipeptides acted as a bitter taste determinant site due to its hydrophobicity. The steric distance between 2 sites was estimated as 4.1 Å from the molecule models of cyclic dipeptides composed of typical amino acids in the bitter peptides. Due to the hypothesis of two bitter taste determinant sites, which bind with the bitter taste receptor via a "binding unit" and a "stimulating unit, " a mechanism for the bitterness in peptides was postulated.
