## 3 Results and Discussion  
Inhibitory Effect of Acidic Amino Acid Residue-Containing Dipeptides on IgE-Mediated degranulation of RBL-2H3 Cells  
This study evaluated the antiallergic effect of acidic amino acids and dipeptides containing an L-glutamic or L-aspartic acid residue in an antigen-induced degranulation assay using RBL-2H3 cells. The result showed that L-glutamic acid is not effective in inhibiting the degranulation of RBL-2H3 cells (Table 1). L-aspartic acid, an anionic amino acid structurally similar to L-glutamic acid, was also investigated; however, no inhibitory effect was observed (Table 1). We then evaluated various dipeptides containing an L-glutamic or L-aspartic acid residue because some dipeptides are known to benefit humans [15]. As a result, L-glutamic acid-containing dipeptides tested in this study inhibited the degranulation of RBL-2H3 cells at 1 mM (Table 1). These peptides suppressed the degranulation in a concentration-dependent manner. The concentration-dependent curve of His-Glu is shown in Figure 1A. The position (carboxy or amino terminus) of L-glutamic acid residue seems to have little effect on the degranulation-inhibitory potency in all samples tested (Table 1). We also evaluated dipeptides containing an L-aspartic acid residue. All of the L-aspartic acid-containing dipeptides tested showed slightly weaker inhibitory effects on the degranulation of RBL-2H3 cells than L-glutamic acid-containing dipeptides (Table 1). Therefore, a shorter side chain of L-aspartic acid residue might be less favorable to the degranulation-inhibitory effect. A strategy to predict and discover novel bioactive peptides using artificial intelligence \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **Relative** & \multicolumn{2}{c}{**Relative**} & \multirow{2}{*}{**Relative Cell**} \\  & **Degranulation-** & & & **Weightity (\%) at** \\  & **Inhibitory Effect (\%)** & & & **Inhibitory Effect (\%)** & **Viability (\%) at** \\  & **at 1 mM** & & & **at 1 mM** & **1 mM** \\ \hline Glutamic acid & \(-1.3\pm 2.0\) & 95.0 \(\pm\) 4.7 & Aspartic acid & \(4.5\pm 1.6\) & \(97.9\pm 2.9\) \\ Glu-Glu & \(16.7\pm 1.0\) & 106.2 \(\pm\) 12.2 & Asp-Asp & \(37.3\pm 1.0\) & \(99.4\pm 3.4\) \\ Glu-Asp & \(51.9\pm 3.9\) & 93.7 \(\pm\) 3.5 & Asp-Glu & \(39.8\pm 2.0\) & \(93.1\pm 1.1\) \\ Glu-Ala & \(38.9\pm 3.3\) & 106.6 \(\pm\) 9.3 & Asp-Ala & \(27.9\pm 1.5\) & \(100.1\pm 8.6\) \\ Ala-Glu & \(45.8\pm 2.5\) & 97.4 \(\pm\) 8.8 & Ala-Asp & \(21.4\pm 1.5\) & \(105.8\pm 4.9\) \\ Glu-Gly & \(47.2\pm 4.3\) & 86.8 \(\pm\) 9.8 & Asp-Gly & \(18.6\pm 0.9\) & \(101.1\pm 7.8\) \\ Gly-Glu & \(31.3\pm 3.1\) & 92.2 \(\pm\) 5.7 & Gly-Asp & \(28.2\pm 0.8\) & \(109.4\pm 11.1\) \\ Glu-His & \(17.1\pm 1.1\) & 93.7 \(\pm\) 9.0 & Asp-His & \(39.4\pm 5.1\) & \(98.3\pm 6.4\) \\ His-Glu & \(41.4\pm 0.5\) & 106.1 \(\pm\) 12.7 & His-Asp & \(39.4\pm 4.4\) & \(93.2\pm 4.4\) \\ Glu-Lys & \(31.5\pm 4.3\) & 105.8 \(\pm\) 9.6 & Asp-Lys & \(31.7\pm 2.3\) & \(116.5\pm 12.8\) \\ Lys-Glu & \(33.4\pm 2.3\) & 90.8 \(\pm\) 4.0 & Lys-Asp & \(28.0\pm 0.8\) & \(115.1\pm 8.5\) \\ Glu-Arg & \(39.3\pm 2.4\) & 96.8 \(\pm\) 3.9 & Asp-Arg & \(22.6\pm 0.2\) & \(104.2\pm 3.0\) \\ Arg-Glu & \(25.7\pm 1.5\) & 93.6 \(\pm\) 0.6 & Arg-Asp & \(41.5\pm 1.7\) & \(111.5\pm 4.2\) \\ Glu-Ser & \(52.3\pm 2.4\) & 94.0 \(\pm\) 7.5 & Asp-Ser & \(23.3\pm 1.5\) & \(95.6\pm 8.2\) \\ Ser-Glu & \(47.1\pm 5.1\) & 97.0 \(\pm\) 2.6 & Ser-Asp & \(27.8\pm 1.5\) & \(96.4\pm 8.1\) \\ Glu-Thr & \(49.9\pm 1.1\) & 97.8 \(\pm\) 11.4 & Asp-Thr & \(21.7\pm 1.5\) & \(94.0\pm 6.4\) \\ Thr-Glu & \(29.2\pm 0.9\) & 102.5 \(\pm\) 8.9 & Thr-Asp & \(19.9\pm 0.9\) & \(107.9\pm 6.3\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Inhibition of antigen-induced degranulation of RBL-2H3 cells by an acidic amino acid or dipeptide. is becoming more prevalent [16]. Utilizing such a strategy may help explain the correlation between dipeptide structure and degranulation-inhibitory activity. No cytotoxicity was observed in any of the tested dipeptides at 1 mM (Table 1).