A novel directed enzymolysis strategy for the preparation of umami peptides in Stropharia rugosoannulata and its mechanism of taste perception

This study aimed to explore the effect of directed enzymolysis on the umami characteristics of S. rugosoannulata, clarify the flavour formation mechanism of umami peptides. We expressed a new aminopeptidase (DNPEP) and obtained the umami peptides of S. rugosoannulata by alkaline protease and DNPEP. The optimal enzymolysis conditions were temperature 55 °C, solid-liquid ratio 1:20 (g/mL), alkaline protease enzymolysis (60 min, 0.5 %, pH 9.0), and DNPEP enzymolysis (80 min, 0.3 %, pH 8.0). The umami peptide components were separated by ultrafiltration and gel filtration chromatography. Six umami peptides (EEAKFN, KAELDLH, LADVEEDK, LKEAHDVA, AHLDYGDGK, and LGKSEDDVSK) were identified by LC-MS/MS and virtual screening, and the umami thresholds of the peptides were 0.15-1.09 mmol/L. Molecular simulations revealed that the amino acid residues Glu301, Ser217, Asp218, and Arg277 were crucial in the binding of the umami peptide to the T1R1/T1R3. Therefore, this study provides a theoretical basis for the development of mushroom condiments.