Identification of Enzymes and Their Key Action Sites for Histamine Degradation in Mulberry Fruit Wine by <i>Lactiplantibacillus plantarum</i>

In this study, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and multicopper oxidase (MCO) of <i>Lactiplantibacillus plantarum</i> W155 with histamine degradation ability were expressed. The mulberry fruit wine (MFW) histamine degradation abilities of GAPDH and MCO were 20.81% and 37.67%, respectively. Compared with the control group, the MFW treated by GAPDH showed higher total phenolic (1.17 g GAE/L) and total flavonoid (0.31 g RE/L) contents, while MFW treated by MCO presented similar total phenolic (1.00 g GAE/L) and total flavonoid (0.29 g RE/L) concentrations. Furthermore, the optimal pH and temperature of GAPDH were 6.0 and 40 °C, respectively, while the optimal pH and temperature of MCO were 3.0 and 50 °C, respectively. Meanwhile, the key action sites for histamine degradation of GAPDH and MCO were minded via homology modeling, molecular docking, and site-directed mutagenesis. Val209 and Ile290 were confirmed as the key action sites for GAPDH, while Qln402 and Leu420 were the pivotal action sites for MCO. Above findings indicated that both GAPDH and MCO of <i>L. plantarum</i> W155 could be used to control the histamine of MFW, and the key action sites of these two enzymes could be used as targets for their subsequent modification.