School of Life Science, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
J Ind Microbiol Biotechnol. 2011 Oct;38(10):1739-46. doi: 10.1007/s10295-011-0963-2. Epub 2011 Mar 31.
Xylulokinase is one of the key enzymes in xylose metabolism and fermentation, and fine-tuned expression of xylulokinase can improve xylose fermentation in yeast. To improve the efficiency of xylose fermentation in Kluyveromyces marxianus, the gene KmXYL3, which encodes a D: -xylulokinase (E.C. 2.7.1.17), was isolated from K. marxianus NBRC1777. KmXYL3 was expressed in Escherichia coli BL21 (DE3) cells, and the specific activity of the resulting recombinant purified xylulokinase was 23.5 mU/mg. Disruption of KmXYL3 resulted in both loss of xylitol utilization and marked decrease in xylose utilization, proving that KmXYL3 encodes a xylulokinase that catalyzes the reaction from xylulose to xylulose 5-phosphate in the xylose metabolic pathway. The slow assimilation of xylose observed in the KmXYL3-disrupted strain indicates that KmXYL3 is critical for xylose and xylitol utilization; however, K. marxianus utilizes a bypass pathway for xylose assimilation, and this pathway does not involve xylitol or xylulose.
木酮糖激酶是木糖代谢和发酵过程中的关键酶之一，精细调节木酮糖激酶的表达可以提高酵母中的木糖发酵效率。为了提高马克斯克鲁维酵母(Kluyveromyces marxianus)中木糖发酵的效率，从马克斯克鲁维酵母 NBRC1777 中分离出编码 D: -木酮糖激酶(E.C. 2.7.1.17)的基因 KmXYL3。KmXYL3 在大肠杆菌 BL21 (DE3)细胞中表达，所得重组纯化木酮糖激酶的比活性为 23.5 mU/mg。KmXYL3 的敲除导致木糖醇利用的丧失和木糖利用的显著下降，证明 KmXYL3 编码的木酮糖激酶催化木糖代谢途径中木酮糖到木酮糖 5-磷酸的反应。在 KmXYL3 敲除菌株中观察到的木糖缓慢同化表明 KmXYL3 对木糖和木糖醇的利用至关重要;然而，马克斯克鲁维酵母利用木糖同化的旁路途径，该途径不涉及木糖醇或木酮糖。
