Three novel umami peptides derived from the alcohol extract of the Pacific oyster ( Crassostrea gigas): identification, characterizations and interactions with T1R1/T1R3 taste receptors

Oyster (Crassostrea gigas), the main ingredient of oyster sauce, has a strong umami taste. In this study, three potential umami peptides, FLNQDEEAR (FR-9), FNKEE (FE-5), and EEFLK (EK-5), were identified and screened from the alcoholic extracts of the oyster (Crassostrea gigas) using nano-HPLC-MS/MS analysis, iUmami-Scoring Card Method (iUmami-SCM) database and molecular docking (MD). Sensory evaluation and electronic tongue analysis were further used to confirm their tastes. The threshold of the three peptides ranged from 0.38 to 0.55 mg/mL. MD with umami receptors T1R1/T1R3 indicated that the electrostatic interaction and hydrogen bond interaction were the main forces involved. Besides, the Phe⁵⁹² and Gln⁸⁵³ of T1R3 were the primary docking site for MD and played an important role in umami intensity. Peptides with two Glu residues at the terminus had stronger umami, especially at the C-terminus. These results contribute to the understanding of umami peptides in oysters and the interaction mechanism between umami peptides and umami receptors.