Insights into the identification of bitter peptides from Jinhua ham and its taste mechanism by molecular docking and transcriptomics analysis

In order to identify the peptides responsible for bitter defects and to understand the mechanism of bitterness in dry-cured ham, the peptides were identified by LC-MS/MS, and the interaction between bitter peptides and receptor proteins were evaluated by molecular docking and molecular dynamics simulation; the signal transduction mechanism of bitter peptides was investigated using the model of HEK-293T cells by calcium imaging and transcriptomics analysis. The results of LC-MS/MS showed that 11 peptides were identified from the high bitterness fraction of defective ham; peptides PKAPPAK, VTDTTR and YIIEK derived from titin showed the highest bitterness values compared with other peptides. The results of molecular docking showed that lower CDOCKER energy was observed in the interaction between these peptides and hT2R16 in comparison with these receptors of hT2R1, hT2R4, hT2R5, hT2R8 and hT2R14, and the interaction of hT2R16 and peptides was stabilized by hydrophobic interaction and hydrogen bond. The average RMSF values of VTDTTR were higher than that of YIIEK and PKAPPAK, while EC50 values of VTDTTR were lower compared with PKAPPAK and YIIEK. Transcriptomics analysis showed that 529 differentially expressed genes were identified in HEK-293T cells during the stimulating by VTDTTR and were mainly enriched into neuroactive ligand-receptor interaction, MAPK pathway, cAMP pathway and calcium signaling pathway, which were mainly responsible for the bitter signal transduction of VTDTTR. These results could provide evidence for understanding the bitter defects of dry-cured ham and the taste mechanism of bitter peptide.