Saccharomyces cerevisiae can obtain xylose utilization capacity via integration of heterogeneous xylose reductase (XR) and xylitol dehydrogenase (XDH) genes into its metabolic pathway, and XYL2 which encodes the XDH plays an essential role in this process. Herein, we reported that two hypothetical XYL2 genes from the multistress-tolerant yeasts of Issatchenkia orientalis and Torulaspora delbrueckii were cloned, and they encoded two XDHs, IoXyl2p and TdXyl2p, respectively, with the activities for oxidation of xylitol to xylulose. Comparative studies demonstrated that IoXyl2p and TdXyl2p, like the SsXyl2p from Scheffersomyces stipitis, were probably localized to the cytoplasm and strictly dependent on NAD⁺ rather than NADP⁺ as the cofactor for catalyzing the oxidation reaction of xylitol. IoXyl2p had the highest specific activity, maximum velocity (V_max), affinity to xylitol (K_m), and catalytic efficiency (k_cat/K_m) among the three XDHs. The optimum temperature for oxidation of xylitol were at 45 °C by IoXyl2p and at 35 °C by TdXyl2p and SsXyl2p, and the optimum pH of IoXyl2p, TdXyl2p and SsXyl2p for oxidation of xylitol was 8.0, 8.5 and 7.5, respectively. Mg²⁺ promoted the activities of IoXyl2p and TdXyl2p, but slightly inhibited the activity of SsXyl2p. Most metal ions had much weaker inhibition effects on IoXyl2p and TdXyl2p than SsXyl2p. IoXyl2p displayed the strongest salt resistance among the three XDHs. To summarize, IoXyl2p from I. orientalis and TdXyl2p from T. delbrueckii characterized in this study are considered to be the attractive candidates for the construction of genetically engineered S. cerevisiae for efficiently fermentation of carbohydrate in lignocellulosic hydrolysate.

酿酒酵母可以通过将异种木糖还原酶（XR）和木糖醇脱氢酶（XDH）基因整合到其代谢途径中来获得木糖利用能力，而编码XDH的XYL2在此过程中起着至关重要的作用。在此，我们报道了两个假设XYL2从的multistress容错酵母基因伊萨侧柏和孢圆酵母德氏克隆，它们编码的两个XDHs，木卫一Xyl2p和Td的Xyl2p，分别与木糖醇氧化成木酮糖的活动。比较研究表明，Io Xyl2p和Td Xyl2p像Ss来自裂殖酵母的Xyl2p可能定位于细胞质，并且严格依赖NAD ⁺而不是NADP ⁺作为催化木糖醇氧化反应的辅助因子。Io Xyl2p在这三个XDH中具有最高的比活，最大速度（V _max），对木糖醇的亲和力（K _m）和催化效率（k _cat / K _m）。木糖醇的氧化的最佳温度是在45℃下通过木卫一Xyl2p和在35℃下通过Td的Xyl2p和SS Xyl2p，并且最适pH木卫一用于氧化木糖醇的Xyl2p，Td Xyl2p和Ss Xyl2p分别为8.0、8.5和7.5。Mg ²⁺促进了Io Xyl2p和Td Xyl2p的活性，但略微抑制了Ss Xyl2p的活性。大多数金属离子对Io Xyl2p和Td Xyl2p的抑制作用比Ss Xyl2p弱得多。Io Xyl2p在三个XDH中显示出最强的耐盐性。总而言之，来自东方伊豆的Io Xyl2p和来自T. delbrueckii的Td Xyl2p在这项研究中表征的特征被认为是构建基因工程酿酒酵母以在木质纤维素水解物中有效发酵碳水化合物的有吸引力的候选者。