Identification of umami peptides from Wuding chicken by Nano-HPLC-MS/MS and insights into the umami taste mechanisms

Wuding chicken is popular with consumers in China because of its umami taste. This study aimed to identify novel umami peptides from Wuding chicken and explore the taste mechanism of umami peptides. The molecular masses and amino acid compositions of peptides in Wuding chicken were identified by nano-scale liquid chromatography-tandem mass spectrometry (Nano-HPLC-MS/MS). The taste characteristics of the peptides synthesized by the solid-phase method were evaluated by sensory evaluation combined with electronic tongue technology. The secondary structure of the peptides was further analyzed by circular dichroism (CD), and the relationship between the structure and taste of the peptides was elucidated by molecular docking. The results showed that eight potential umami peptides were identified, among which FVT (FT-3), LDF (LF-3), and DLAGRDLTDYLMKIL (DL-15) had distinct umami tastes, and FT-3 had the highest umami intensity, followed by LF-3 and DL-15. The relative contents of β-sheets in the three umami peptides were 55.20%, 57.30%, and 47.70%, respectively, which were the key components of Wuding chicken umami peptides. In addition to LF-3 embedded in the cavity-binding domain of the TIR1, both FT-3 and DL-15 were embedded in the venus flytrap domain (VFTD) of the T1R3 to bind the umami receptor T1R1/T1R3. The main binding forces between the umami peptides and the umami receptor T1R1/T1R3 relied on hydrogen bonds and hydrophobic interactions, and the key amino acid residues of the combination of umami peptides and the umami receptor T1R1/T1R3 were Glu292, Asn235, and Tyr262.