酵母细胞催化合成 18α-甘草酸

18α-Glycyrrhizin (18α-GL) is an oleanane-type saponin. 18α-GL is less polar and more lipophilic than its diastereomer 18β-GL. Its stronger anti-toxic and anti-inflammatory effects and higher liver targeting make 18α-GL a major drug ingredient in the field of liver protection. However, the current preparation method of 18α-GL is highly polluting and has low efficiency. Therefore, there is an urgent need to develop a green and simple method to synthesize 18α-GL. Glycosyltransferases were heterologously expressed in yeast cells. Through whole-cell catalysis, glycosyltransferases cGuCSyGT was identified as being able to catalyze the specific synthesis of 18α-glycyrrhetinic acid 3-O-monoglucuronide (18α-GAMG) from 18α-glycyrrhetinic acid (18α-GA) and GgUGT1 was identified as being able to catalyze the specific synthesis of 18α-glycyrrhizin (18α-GL) from 18α-GAMG. We further employed protein structure prediction and molecular dynamics simulation to explore the reason why cGuCSyGT has lower catalytic activity for 18α-GA than 18β-GA. Finally, an optimal process for yeast catalytic synthesis of 18α-GAMG and 18α-GL was constructed by optimizing various parameters, including substrate addition concentration, chassis host cells, substrate addition time, catalytic time, medium component addition and substrate solvent. Thus, the production of 18α-GAMG and 18α-GL reached (36.38±1.87) mg/L and (39.32±0.75) mg/L, respectively. This research achieved the microbial catalytic synthesis of 18α-GAMG and 18α-GL, which will provide a theoretical basis and technical support for the total microbial synthesis of 18α-GL.