Structural basis of mannitol-induced activation of human taste receptor PKD2L1

Sour taste is generally considered as a non-preferred taste, but many organisms, including humans, evolved to consume sour-tasting foods. PKD2L1 is a proton-activated sour taste receptor. In this study, we found that mannitol, known to produce a sweet taste, acts on hPKD2L1 in a concentration-dependent and pH-sensitive manner, and in silico protein-ligand complex modeling indicated that D523 of PKD2L1 was the critical binding residue. When comparing the Vmax value, it was confirmed that the wild type has 55.7 +/- 2.94 but changed to 0 +/- 0 in the D523A mutant type. Fermented kimchi maintains an average pH of 3.5-4.5, and this low-pH condition supports the production of sweet and sour tastes by mannitol. A considerable quantity of mannitol is produced by heterofermentative lactic acid bacteria during fermentation of kimchi, and the acidity of kimchi increases after fermentation, which may impart a unique sweet and refreshing taste compared with fresh kimchi. These findings indicate that the differences in mannitol-induced taste perception, especially sour taste, depend on pH levels, which could help explain the conjugative taste perception associated with fermented kimchi.

Automated summary

This study reveals that the PKD2L1 sour taste receptor can be affected by mannitol in a concentration-dependent and pH-sensitive manner. The production of mannitol during the fermentation of kimchi contributes to the sweet and sour tastes, which may explain the unique taste associated with fermented kimchi.