Abstract
A novel β-glucosidase (Thglu3) was identified from Thermotoga sp. which had biotransformation activity for notoginsenoside R1 (NR-R1). Sequence analysis of Thglu3 revealed that it could be classified into glycoside hydrolase family 3 (GH3). The gene encoding a 719-amino acid protein was cloned and expressed in Escherichia coli. The recombinant enzyme was purified, and its molecular weight was approximately 81 kDa. The recombinant Thglu3 exhibited an optimal activity at 75 °C and pH 6.4. The β-glucosidase had high selectivity for cleaving the outer glucose moiety at the C20 position of NR-R1, which produced the more pharmacologically active notoginsenoside R2 (NR-R2). Under the optimal reaction conditions for gram-scale production, 30 g NR-R1 was transformed to NR-R2 using 20 g crude enzyme at pH 6.4 and 75 °C within 1 h with a molar yield of 93%. This study was the first report of the highly efficient and selective gram-scale transformation of NR-R2 from NR-R1 by a thermophilic β-glucosidase.