Comparison on inhibitory effect and mechanism of inhibitors on sPPO and mPPO purified from ‘Lijiang snow’ peach by combining multispectroscopic analysis, molecular docking and molecular dynamics simulation

The inhibition mechanisms of soluble PPO (sPPO) by l-cysteine, reduced glutathione and thiourea, and membrane-bound (mPPO) by l-cysteine, reduced glutathione, thiourea, anisaldehyde and cinnamaldehyde were investigated by combining multispectroscopic analysis and computational simulations. Reduced glutathione showed the strongest inhibitory effect, with IC50 of 0.46 and 0.94 mM, respectively. The multispectral results showed that all inhibitors inhibited activity by destroying the secondary and tertiary structure, and the structure of sPPO were more easily affected. Docking showed that hydrogen bond and metal contact were the main driving force for inhibitors binding to sPPO and mPPO, respectively. Simulation showed that sPPO-inhibitor system had more fluctuation than mPPO-inhibitor system, indicating easier inhibition of sPPO activity. This work revealed that the structural differences between sPPO and mPPO led to different inhibition mechanisms of PPOs by inhibitors at the molecular level, which could provide the guidance for the selection of inhibitors in fruit and vegetable processing.