Novel glycosidase from Paenibacillus lactis 154 hydrolyzing the 28-O-β-d-glucopyranosyl ester bond of oleanane-type saponins

Abstract Oleanane-type ginsenosides are a class of compounds with remarkable pharmacological activities. However, the lack of effective preparation methods for specific rare ginsenosides has hindered the exploration of their pharmacological properties. In this study, a novel glycoside hydrolase Pl GH3 was cloned from Paenibacillus lactis 154 and heterologous expressed in Escherichia coli . Sequence analysis revealed that Pl GH3 consists of 749 amino acids with a molecular weight of 89.5 kDa, exhibiting the characteristic features of the glycoside hydrolase 3 family. The enzymatic characterization results of Pl GH3 showed that the optimal reaction pH and temperature was 8 and 50 °C by using p -nitrophenyl- β - d -glucopyranoside as a substrate, respectively. The K m and k cat values towards ginsenoside Ro were 79.59 ± 3.42 µM and 18.52 s −1 , respectively. Pl GH3 exhibits a highly specific activity on hydrolyzing the 28- O - β - d -glucopyranosyl ester bond of oleanane-type saponins. The mechanism of hydrolysis specificity was then presumably elucidated through molecular docking. Eventually, four kinds of rare oleanane-type ginsenosides (calenduloside E, pseudoginsenoside RP1, zingibroside R1, and tarasaponin VI) were successfully prepared by biotransforming total saponins extracted from Panax japonicus . This study contributes to understanding the mechanism of enzymatic hydrolysis of the GH3 family and provides a practical route for the preparation of rare oleanane-type ginsenosides through biotransformation. Key points • The glucose at C-28 in oleanane-type saponins can be directionally hydrolyzed. • Mechanisms to interpret PlGH3 substrate specificity by molecular docking. • Case of preparation of low-sugar alternative saponins by directed hydrolysis.