# Ethanol Regulates Bitterness Perception of the Trp-Ile-Lys-Lys (WIKK) Peptide by Activating the Human Bitter Receptor T2R47

## TL;DR

This study shows how ethanol affects the bitterness of a specific peptide by interacting with a human bitter receptor, explaining part of the flavor complexity in Chinese Baijiu.

## Contribution

The study reveals a novel molecular mechanism by which ethanol modulates bitter peptide perception through the T2R47 receptor.

## Key findings

- WIKK peptide has higher taste thresholds in ethanol–water mixtures than in water.
- Ethanol potentiates WIKK’s activation of the T2R47 bitter receptor in a non-monotonic manner.
- Molecular simulations show ethanol alters WIKK’s binding affinity to T2R47 via key amino acid interactions.

## Abstract

This study investigated the modulatory mechanism of ethanol on bitter peptide perception using ethanol–water mixture models (38–62% ethanol) to elucidate the impact of bitter peptides on the sensory quality of Chinese Baijiu. Identified by the TastePeptidesDB and sensory evaluation, Trp-Ile-Lys-Lys (WIKK) exhibited markedly higher taste thresholds in ethanol–water than in water, and ethanol modulated WIKK’s bitterness threshold through a non-monotonic pattern. Plasmid transfection and a Fluo-4 AM-based, flow-cytometric calcium mobilization assay in HEK293T cells confirmed that WIKK activated the human bitter receptor T2R47 with ethanol potentiating this activation. Molecular docking and dynamics simulations demonstrated WIKK bound human bitter receptor T2R47 primarily through H-bonds, π–π, and π–alkyl interactions in the ethanol–water system with the key binding sites of TRP88, HIS65, TYR85, ILE82, and ARG81, and ethanol significantly altered this binding affinity. These results elucidate ethanol’s role in modulating peptide bitterness perception and the underlying molecular mechanisms, enhancing the understanding of Baijiu flavor complexity.