Abstract：
The transgalactosylase activity of β-galactosidases offers a convenient and promising strategy for conversion of lactose into high-value oligosaccharides, such as galacto-oligosaccharides (GOS) and human milk oligosaccharides (HMOs). In this study, we cloned and biochemically characterized a novel C-terminally truncated β-galactosidase (PaBgal2A-D) from Paenibacillus antarcticus with high transglycosylation activity. PaBgal2A-D is a member of glycoside hydrolase (GH) family 2. The optimal pH and temperature of PaBgal2A-D were determined to be pH 6.5 and 50°C, respectively. It was relatively stable within pH 5.0-8.0 and up to 50°C. PaBgal2A-D showed high transglycosylation activity for GOS synthesis, and the maximum yield of 50.8% (wt/wt) was obtained in 2 h. Moreover, PaBgal2A-D could synthesize lacto-N-neotetraose (LNnT) using lactose and lacto-N-triose II (LNT2), with a conversion rate of 16.4%. This study demonstrated that PaBgal2A-D could be a promising tool to prepare GOS and LNnT.
摘要：
β-半乳糖苷酶的转半乳糖基酶活性为乳糖转化为高价值寡糖提供了一种方便且有前途的策略。例如低聚半乳糖(GOS)和人乳寡糖(HMO)。在这项研究中,我们克隆了一种新型的C末端截短的β-半乳糖苷酶（PaBgal2A-D），并进行了生化鉴定，该酶具有高的转糖基化活性。PaBgal2A-D是糖苷水解酶(GH)家族2的成员。确定PaBgal2A-D的最佳pH和温度为pH6.5和50°C，分别。在pH5.0-8.0和高达50°C内相对稳定。PaBgal2A-D对GOS合成显示出高的转糖基化活性，在2h内获得50.8%(wt/wt)的最大产率。PaBgal2A-D可以使用乳糖和乳糖-N-三糖II（LNT2）合成乳糖-N-新四糖（LNnT），转化率为16.4%。这项研究表明，PaBgal2A-D可能是制备GOS和LNnT的有前途的工具。
