Department of Biotechnology and Chemical Technology, Aalto University, P.O. Box 6100, FIN-02015 Espoo, Finland.
Enzyme Microb Technol. 2012 Jan 5;50(1):71-6. doi: 10.1016/j.enzmictec.2011.09.009. Epub 2011 Sep 29.
L-Xylulose was used as a raw material for the production of L-xylose with a recombinantly produced Escherichia coli L-fucose isomerase as the catalyst. The enzyme had a very alkaline pH optimum (over 10.5) and displayed Michaelis-Menten kinetics for L-xylulose with a K(m) of 41 mM and a V(max) of 0.23 μmol/(mg min). The half-lives determined for the enzyme at 35 °C and at 45 °C were 6h 50 min and 1h 31 min, respectively. The reaction equilibrium between L-xylulose and L-xylose was 15:85 at 35 °C and thus favored the formation of L-xylose. Contrary to the L-rhamnose isomerase catalyzed reaction described previously [14]L-lyxose was not detected in the reaction mixture with L-fucose isomerase. Although xylitol acted as an inhibitor of the reaction, even at a high ratio of xylitol to L-xylulose the inhibition did not reach 50%.
木酮糖被用作生产 L-木糖的原料，使用重组大肠杆菌 L-岩藻糖异构酶作为催化剂。该酶具有非常碱性的 pH 最佳值（超过 10.5），并对 L-木酮糖表现出米氏动力学，K(m)为 41mM，V(max)为 0.23μmol/(mg min)。在 35°C 和 45°C 下测定的酶半衰期分别为 6 小时 50 分钟和 1 小时 31 分钟。在 35°C 下，L-木酮糖和 L-木糖之间的反应平衡为 15:85，因此有利于 L-木糖的形成。与之前描述的 L-鼠李糖异构酶催化的反应[14]相反，在 L-岩藻糖异构酶的反应混合物中未检测到 L-来苏糖。尽管木糖醇作为反应的抑制剂，但即使在木糖醇与 L-木酮糖的高比例下，抑制作用也未达到 50%。
