A Novel β-Glucuronidase from Talaromyces pinophilus Li-93 Precisely Hydrolyzes Glycyrrhizin into Glycyrrhetinic Acid 3- O -Mono-β- d -Glucuronide

Compared to chemical methods, the biotransformation of glycyrrhizin (GL) into glycyrrhetinic acid 3- O -mono- β - d -glucuronide (GAMG), which has a higher sweetness and stronger pharmacological activity than those of GL, via catalysis by β -glucuronidase is an environmentally friendly approach due to the mild reaction conditions and the high yield of GAMG. However, currently available GUSs show low substrate specificity toward GL and further hydrolyze GAMG to glycyrrhetinic acid (GA) as a by-product, increasing the difficulty of subsequent separation and purification. In the present study, we succeeded in isolating a novel β -glucuronidase (named TpGUS79A) from Talaromyces pinophilus Li-93 that specifically hydrolyzes GL to GAMG without the formation of GA. TpGUS79A also shows higher activity on GL than those of the previously characterized GUSs. Moreover, the gene for TpGUS79A was cloned and its function verified by heterologous expression in P. pastoris . Therefore, TpGUS79A can serve as a powerful biocatalyst for the cost-effective production of GAMG through GL transformation.