Department of Bioscience and Biotechnology, Konkuk University, Seoul, Republic of Korea.
Biotechnol Lett. 2012 Nov;34(11):2061-8. doi: 10.1007/s10529-012-0999-z. Epub 2012 Jul 11.
A recombinant putative N-acyl-D-glucosamine 2-epimerase from Dictyoglomus turgidum was identified as a cellobiose 2-epimerase by evaluating its substrate specificity. The purified enzyme was a 46 kDa monomer with a specific activity of 16.8 μmol min(-1) mg(-1) for cellobiose. The epimerization activity was maximal at pH 7.0 and 70 °C with a half-life of 55 h. The isomerization of the glucose at the reducing end of β-1,4- and α-1,4-linked gluco-oligosaccharides to a fructose moiety by the enzyme took place after the epimerization of the glucose to a mannose moiety. The enzyme converted cellobiose to 12.8 % 4-O-β-D-glucopyranosyl-D-mannose and 54.6 % 4-O-β-D-glucopyranosyl-D-fructose as an equilibrium and converted lactose to 12.8 % epilactose and 54.3 % lactulose.
从 Dictyoglomus turgidum 中鉴定出一种重组的假定 N-酰基-D-葡糖胺 2-差向异构酶，通过评估其底物特异性将其鉴定为纤维二糖 2-差向异构酶。纯化的酶为 46 kDa 的单体，纤维二糖的比活性为 16.8 μmol min(-1) mg(-1)。在 pH 7.0 和 70°C 下，酶的最适活性最大，半衰期为 55 小时。β-1,4-和 α-1,4-连接的葡糖基低聚糖的还原端的葡萄糖异构化为果糖部分，这是在葡萄糖差向异构化为甘露糖部分之后发生的。该酶将纤维二糖转化为 12.8%的 4-O-β-D-吡喃葡萄糖基-D-甘露糖和 54.6%的 4-O-β-D-吡喃葡萄糖基-D-果糖，达到平衡，并将乳糖转化为 12.8%的表乳糖和 54.3%的乳果糖。
