Peptide sweet taste

Sweetness Production by the Combination of Bitter and Sweet Tastes. Sensory tests using typically bitter compounds such as brucine, strychnine, phenylfiiiourea, caffeine and bitter peptides were performed. Sensory tests using typically bitter compounds such as brucine, strychnine, phenylthiourea, caffeine and bitter peptides were performed. Sensory taste impression were also measured for combinations of acetic acid (sour) and typical bitter compounds (5). The data from these studies indicated that the tastes of ese bitter/sour mixtures changed to a sweet taste regardless of their chemical structure of the bitter component (Table II). 

Taste of Dipeptides Containing Lys and/or Gly. Since Lys-Gly HCl produces the saltiness, we prepared some dipeptides composed of Lys and/or Gly. The results are listed in Table XI. Gly-Lys, of which the amino acid sequence is opposite to the salty peptide Lys-Gly-HCl, produced a weakly sweet taste instead of the salty taste. Dipeptide composed of only Lys or Gly did not any taste. 

The analysis, in composite over the four classes of L-aspartyl dipeptides suggests that the electron-withdrawing effect of substituents directed to the peptide bond, and the steric dimensions of the molecules, are important in eliciting the sweet taste. The values of the regression coefficients of the a term in the QSAR equations for L-aspartic acid amides, L-aspartylaminoethylesters, and L-aspartylaminopropionates all... 

Aspartame. Aspartame [22839-47-0] [53906-69-1] (APM, L-aspartyl-L-phenylalanine methyl ester) (1), also known under the trade names of NutraSweet and EQUAL, is the most widely used nonnutritive sweetener worldwide. This dipeptide ester was synthesized as an intermediate for an antiulcer peptide at G. D. Searle in 1965. Although this compound was known in the literature, its sweet taste was serendipitously discovered when a chemist licked his finger which was contaminated with it. Many analogues, especially the more stable esters, were made (6) and their taste qualities and potencies determined. It was the first compound to be chosen for commercial development. Following the purchase of G. D. Searle by Monsanto, the aspartame business was split off to become a separate Monsanto subsidiary called the NutraSweet Company. 

Other peptides, such as L-aspartyl-L-phenylalanine methyl ester (aspartame), have a sweet taste. Several studies have been carried out to relate the structure and taste of analogs of this dipeptide (25). Tsang et al. (26) reported that the analogs at the lower end of the L-aspartyl-a-aminocycloalkanecarboxylic acid methyl ester series were sweet, the dipeptides containing a-... 

After the finding of a sweet taste in L-Asp-L-Phe-OMe (aspartame) by Mazur et at. (6), a number of aspartyl dipeptide esters were synthesized by several groups in order to deduce structure-taste relationships, and to obtain potent sweet peptides. In the case of the peptides, the configuration and the conformation of the molecule are important in connection with the space-filling properties. The preferred conformations of amino acids can be shown by application of the extended Hiickel theory calculation. However, projection of reasonable conformations for di- and tripeptide molecules is not easily accomplished. 

The sweet-tasting property of aspartyl dipeptide esters has been successfully explained on the basis of the general structures shown in Figure 1 (4). A peptide will taste sweet when it takes... 

The structure-taste relationships will be discussed in detail. Dipeptide esters are closely related to amino acids in chemical structure and properties. Hence, we selected amino acids as the standard to which sweet peptides were related. The structural features of sweet-tasting amino acids have been best explained by Kaneko (12) as shown in Figure 2, in which an amino acid will taste sweet when R2 is H, CH3 or C2H5, whereas the size of Ri is not restricted if the amino acid is soluble in water. 

B). This also suggests that the AH-B concept represents only a first approximation in the case of peptides. Certainly, the AH-B system is required in the molecule. However, the structural characteristics of the second amino acid sometimes may completely mask any AH-B effect. To test the above hypothesis, we have synthesized a number of peptides with or without a sweet taste. 

The studies on peptides began with a correlation between sweet amino acids and peptides. Since the projection formula of L-Asp-Gly-OMe (4) is similar in size and shape to that of e-Ac-D-Lys (3) which is sweet, we predicted that L-Asp-Gly-OMe would taste sweet in spite of the bitter taste in the literature. Therefore, we synthesized the peptide and tasted it. As expected, it was sweet and its sweetness potency was almost equal to that of e-Ac-D-Lys. Thus, the dipeptide could be correlated to the amino acid. Lengthening (5) or enlargement (6) of the alkyl group of the ester did not affect its sweetness potency (Table 1). 

Therefore, we have concluded that sweet-tasting aspartyl dipeptide esters can be drawn as the unified formula (A), whereas nonsweet peptides as (B) as shown in Figure 1. 

Finally, L-Asp-D-Val-Gly-OMe (41) was synthesized in order to see whether it remained sweet. The peptide was devoid of sweetness and almost tasteless, though D-valine-containing aspartyl dipeptide esters such as L-Asp-D-Val-0Pr (17) and L-Asp-D-Val-OPrt (8, 17), which are similar to the tripeptide ester in size and shape and have potent sweet taste. 

One problem that remains is the mode of interaction between the sweet peptides and the receptor site. Despite a great number of studies, the mechanism of action of sweet stimuli on the receptor is not well known. Stereoisomerism can be responsible for differences in taste responses, and space-filling properties are also very important. These facts suggest that the receptor site exists in a three-dimensional structure. In this connection, the sense of sweet taste is subject to the "lock and key" of biological activity. 

In nature, the amino acids are combined to give proteins with hundreds or even thousands of amino acids in each one. Small assemblies of amino acids are known as peptides and die amide bond that links them is called a peptide bond. One important dipeptide is the sweetening agent aspartame, whose synthesis was discussed in Chapter 25. It is composed (and made) of the amino acid aspartic acid (Asp) and the methyl ester of phenylalanine. Only this enantiomer has a sweet taste and it is very sweet indeed—about 160 times as sweet as sucrose. 

The sweet peptide, aspartame (L-Asp-L-Phe-OMe) which has a sweet taste 180 times that of sucrose, was discovered by Mazur al. (2) Aspartame is stable at pH 4 and unstable at pH 1 or 7-8. It is also unstable at high temperatures. Under these unstable conditions, the... 

Yamazaki, T., Benedetti, E., Kent, D., and Goodman, M. (1994). Conformational requirements for sweet-tasting peptides and peptidomimetics. Angew. Chem. Int. Ed. Engl. 33, 1437-1451. 

The different stereochemistry of the two peptides leads to different binding with taste receptors and therefore to the sweet taste for one and to the bitter taste for the other. 

Sweet proteins, proteins and peptides that elicit sweet taste. Thaumatin, mondlin, mabinlin, brazzein, egg lysozyme, and neoculin (previously named curculin) have been identified as sweet-tasting proteins. New G protein-coupled receptors have been... 

Conformational Requirements for Sweet-Tasting Peptides and Peptidomi-... 

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