In this study, a α-l-rhamnosidase gene from Bacteroides thetaiotaomicron VPI-5482 was cloned and expressed in Escherichia coli. The specific activity of rhamnosidase was 0.57 U/mg in LB medium with 0.1 mM Isopropyl β-d-Thiogalactoside (IPTG) induction at 28 °C for 8 h. The protein was purified by Ni-NTA affinity, which molecular weight approximately 83.3 kDa. The characterization of BtRha was determined. The optimal activity was at 55 °C and pH 6.5. The enzyme was stable in the pH range 5.0–8.0 for 4 h over 60%, and had a 1-h half-life at 50 °C. The Kcat and Km for p-nitrophenyl-α-l-rhamnopyranoside (pNPR) were 1743.29 s⁻¹ and 2.87 mM, respectively. The α-l-rhamnosidase exhibited high selectivity to cleave the α-1,2 and α-1,6 glycosidic bond between rhamnoside and rhamnoside, rhamnoside and glycoside, respectively, which could hydrolyze rutin, hesperidin, epimedin C and 2″-O-rhamnosyl icariside II. Under the optimal conditions, BtRha transformed epimedin C (1 g/L) to icariin by 90.5% in 4 h. This study provides the first demonstration that the α-l-rhamnosidase could hydrolyze α-1,2 glycosidic bond between rhamnoside and rhamnoside.

在该研究中，克隆了来自拟杆菌（Bacteroides thetaiotaomicron） VPI-5482的α- 1-鼠李糖苷酶基因，并在大肠杆菌中表达。在具有0.1 mM异丙基β- d-硫代半乳糖苷（IPTG）的LB培养基中，鼠李糖苷酶的比活性为0.57 U / mg，在28°C下诱导8 h。通过分子量约为83.3 kDa的Ni-NTA亲和力纯化蛋白质。确定了BtRha的特征。最佳活性是在55°C和pH 6.5下。该酶在60％的pH范围内（5.0-8.0）稳定4小时，在50°C时具有1小时半衰期。所述的Kcat和公里为p硝基苯基α-升-rhamnopyranoside（pNPR）分别为1743.29 s ^-1和2.87 mM。α- 1-鼠李糖苷酶对鼠李糖苷和鼠李糖苷，鼠李糖苷和糖苷之间的α-1,2和α-1,6糖苷键均具有很高的选择性，可水解芦丁，橙皮苷，淫羊med苷C和2” -O -鼠李糖基糖苷II。在最佳条件下，BtRha在4小时内将Epimedin C（1 g / L）转化为甘菊素90.5％。该研究首次证明了α- 1-鼠李糖苷酶可以水解鼠李糖苷和鼠李糖苷之间的α-1,2糖苷键。