We isolated a β-N-acetylglucosaminidase encoding gene from the filamentous fungus Aspergillus oryzae, and designated it nagA. The nagA gene encoded a polypeptide of 600 amino acids with significant similarity to glucosaminidases and hexosaminidases of various eukaryotes. A. oryzae strain carrying the nagA gene under the control of the improved glaA promoter produced large amounts of β-N-acetylglucosaminidase in a wheat bran solid culture. The β-N-acetylglucosaminidase was purified from crude extracts of the solid culture by column chromatographies on Q-Sepharose and Sephacryl S-200. This enzyme was used for synthesis of lacto-N-triose II, which is contained in human milk. By reverse hydrolysis reaction, lacto-N-triose II and its positional isomer were synthesized from lactose and D-N-acetylglucosamine in 0.21% and 0.15% yield, respectively.
我们从丝状真菌黑曲霉(Aspergillus oryzae)中分离出了一个β-N-乙酰
葡萄糖氨糖苷酶编码
基因,并将其命名为 nagA。nagA
基因编码 600 个
氨基酸的
多肽,与各种真核
生物的
葡糖胺酶和己糖胺酶非常相似。携带 nagA
基因的 A. oryzae 菌株在改良的 glaA 启动子控制下,在麦麸固体培养物中产生了大量的 β-N-乙酰
葡糖苷酶。通过在 Q-Sepharose 和 Sephacryl S-200 上进行柱层析,从固体培养物的粗
提取物中纯化出了β-N-乙酰
葡糖苷酶。这种酶被用于合成母乳中含有的
乳糖-N-三糖 II。通过反向
水解反应,从
乳糖和 D-N-乙酰
葡糖胺合成了乳-N-三糖 II 及其位置异构体,产率分别为 0.21% 和 0.15%。