Comparison of Umami Peptides Obtained by in vitro and in silico Enzymatic Hydrolysis from Tiger Shrimp (Penaeus monodon), Interaction Mechanism with Umami Receptors and Peptide Sequence Reconstruction

Background: Umami is one of the basic taste sensations, and the methods for preparing umami peptides mainly include in vitro and in silico enzymatic hydrolysis methods. Most studies have used only one of the techniques to obtain umami peptides, and there are fewer studies on the simultaneous use of both methods to obtain umami peptides; therefore, we obtained umami peptides from tiger shrimp by two methods and compared the differences between the umami peptides obtained by the two methods. Methods: In this study, umami peptides were prepared by in vitro and in silico enzymatic hydrolysis techniques, respectively, and the umami properties of the obtained umami peptides were verified by sensory evaluation and e-tongue. These umami peptides had good umami scores, low umami thresholds, and ACWVPCEK had an umami-enhancing effect. The umami peptides obtained by in vitro enzymatic hydrolysis had good richness. Finally, structural modification was achieved by conjugating Asp/Glu (D/E) residues to the N/C- termini of the peptides. Results: The in vitro enzymatic hydrolysis-derived peptides exhibited stronger umami properties and significantly lower taste thresholds. Furthermore, molecular docking analysis (Vina scores) indicated their higher stability in binding to T1R1/T1R3 receptors. The results of molecular docking studies of umami peptides obtained by in vitro enzymatic hydrolysis showed that conventional hydrogen bonding and van der Waals forces were the main forces for binding of umami peptides to the receptor, and SER104, ASN68 and HIS145 were the key binding sites. Reconstruction of the peptide sequence after the D/E consensus effect lowers the peptide's umami taste threshold. Conclusions: In vitro enzymatic hydrolysis allows for more efficient preparation of umami peptides. The in silico enzymatic hydrolysis was selected to be carried out using myosin of tiger shrimp, which is abundant in shrimp but may not be the main source of umami in shrimp; the in vitro enzymatic hydrolysis was validated the umami of different fractions during isolation and purification, and the fractions with the strongest umami were selected for the next experiments, which may be the reasons for the better effect of umami peptides obtained through in vitro enzymatic hydrolysis. To improve the umami properties of umami peptides obtained by in silico enzymatic hydrolysis, the sequence was rationally designed using the D/E consensus effect to lower the threshold of umami peptides, suggesting the D/E consensus effect improves the umami properties of peptides. The study compares the difference between the umami peptides prepared by the two methods for the preparation of umami peptides and elucidates the mechanism of umami perception in tiger shrimp and provides ideas for effective screening of umami peptides and provides a reference for the enhancement of umami through the rational design of peptides.