Abstract: In order to discover new umami peptides and explore their structure-activity relationship, this study separated and purified umami peptides from the muscle of cultured Takifugu obscurus using 60% aqueous ethanol solution as the extraction solvent, as well as applying ultrafiltration and gel chromatography combined with sensory evaluation. The molecular masses and amino acid compositions of the peptides were further identified by nano-liquid chromatography-quadrupole orbitrap mass spectrometry. The taste characteristics of the peptides synthesized by the solid-phase method were evaluated by sensory evaluation combined with electronic tongue, and their structure-activity relationship was elucidated by molecular docking. The results indicated that seven umami peptides including NWDDMEK, KTGLSPDQF, KTDLNFENL, ASLDGEFKG, ALASLDGEFKG, ALTSLDGEFKG and RLGSSEVEQVQ were identified with a molecular mass in the range of 922.3–1 230.6 Da, and their umami thresholds ranged from 0.38 to 1.04 mmol/L. Glutamic acid (Glu), aspartic acid (Asp) and lysine (Lys) residues in the peptide sequences, and the amino acid residues N69, S276, R151, R277, A302, T149 and N150 in the umami receptor T1R1/T1R3 played important roles in the umami taste of the peptides. This study may guide future studies to elucidate the umami taste of peptides.

Key words: umami peptides; Takifugu obscurus; taste characteristics; umami threshold; molecular docking