Mechanism of molecular interaction between pyrazine flavor substances and Lysozyme: Based on spectroscopy and molecular docking studies

Volatile flavor substances in food have received greater attention owing to the love for flavored foods. In this study, a series of spectroscopic and molecular docking techniques were employed to explore the mechanism of interaction between pyrazine flavor substances (a variety of cocoa flavoring compounds used as spices), and lysozyme (Lyz, a basic protein), and to understand the possible effect of volatile flavor substances on the structure and conformation of endogenous proteins. The results indicated that static quenching was the major mechanism for pyrazine flavor substances-Lyz interactions, and it was confirmed using UV-Vis spectroscopy. Further, synchronous fluorescence, circular dichroism and three-dimensional fluorescence measurements confirmed that the conformation of pyrazine flavor substances-Lyz changed; the close binding between pyrazine flavor substances and Lyz destroyed the natural hydrogen bond grid structure of Lyz; the amino acid microenvironment changed. All of them led to the gradual release of the Lyz α-Helix structure. In addition, the combination of thermodynamic analysis and molecular docking studies revealed that the binding of pyrazine flavor substances to Lyz was spontaneous, and it was attributed mainly by the formation of pi-alkyl hydrophobic interactions using amino acid residues namely, TRP64 and VAL110. In conclusion, the spectroscopic measurements and molecular docking studies indicated that pyrazine flavor substances have an effect on the conformation of Lyz, which provides a theoretical basis for the interaction between flavor substances and proteins. This study also provides vital information about the transport and mechanisms of action of pyrazine flavor substances and Lyz in human body that are used in enhancing the safety of food and medicine.