Institute of Natural Resources and Geographic Information Technology, College of Resources, Sichuan Agricultural University, No. 211 Huimin Road, Wenjiang, 611130, Sichuan, People's Republic of China.
College of Environmental Sciences, Sichuan Agricultural University, Wenjiang, 611130, Sichuan, People's Republic of China.
Appl Microbiol Biotechnol. 2017 Dec;101(23-24):8405-8418. doi: 10.1007/s00253-017-8567-z. Epub 2017 Oct 15.
Aldehydes generated as by-products during the pretreatment of lignocellulose are the key inhibitors to Saccharomyces cerevisiae, which is considered as the most promising microorganism for industrial production of biofuel, xylitol as well as other special chemicals from lignocellulose. S. cerevisiae has the inherent ability to in situ detoxify aldehydes to corresponding alcohols by multiple aldehyde reductases. Herein, we report that an uncharacterized open reading frame YKL071W from S. cerevisiae encodes a novel "classical" short-chain dehydrogenase/reductase (SDR) protein with NADH-dependent enzymatic activities for reduction of furfural (FF), glycolaldehyde (GA), formaldehyde (FA), and benzaldehyde (BZA). This enzyme showed much better specific activities for reduction of GA and FF than FA and BZA, and displayed much higher Km and Kcat/Km but lower Vmax and Kcat for reduction of GA than FF. For this enzyme, the optimum pH was 5.5 and 6.0 for reduction of GA and FF, and the optimum temperature was 30 °C for reduction of GA and FF. Both pH and temperature affected stability of this enzyme in a similar trend for reduction of GA and FF. Cu, Zn, Ni, and Fe had severe inhibition effects on enzyme activities of Ykl071wp for reduction of GA and FF. Transcription of YKL071W in S. cerevisiae was significantly upregulated under GA and FF stress conditions, and its transcription is most probably regulated by transcription factor genes of YAP1, CAD1, PDR3, and STB5. This research provides guidelines to identify more uncharacterized genes with reductase activities for detoxification of aldehydes derived from lignocellulose in S. cerevisiae.
木质纤维素预处理过程中产生的醛类是酿酒酵母的关键抑制剂，酿酒酵母被认为是工业生产生物燃料、木糖醇和其他木质纤维素特殊化学品最有前途的微生物。酿酒酵母具有内在的能力，通过多种醛还原酶将醛原位解毒为相应的醇。在此，我们报告酿酒酵母中一个未被描述的开放阅读框 YKL071W 编码一种新型的“经典”短链脱氢酶/还原酶（SDR）蛋白，该蛋白具有 NADH 依赖性酶活性，可还原糠醛（FF）、乙二醇醛（GA）、甲醛（FA）和苯甲醛（BZA）。该酶对 GA 和 FF 的还原具有更好的比 FA 和 BZA 更高的特异性活性，并且对 GA 的 Km 和 Kcat/Km 更高，而对 FF 的 Vmax 和 Kcat 较低。对于该酶，还原 GA 和 FF 的最适 pH 值分别为 5.5 和 6.0，最适温度分别为 30°C。GA 和 FF 的还原均受 pH 和温度的影响，稳定性呈相似趋势。Cu、Zn、Ni 和 Fe 对 Ykl071wp 还原 GA 和 FF 的酶活性有严重的抑制作用。在 GA 和 FF 胁迫条件下，酿酒酵母中 YKL071W 的转录显著上调，其转录很可能受 YAP1、CAD1、PDR3 和 STB5 转录因子基因的调控。本研究为鉴定酿酒酵母中具有还原酶活性的更多未被描述的基因，以解毒木质纤维素衍生的醛类提供了指导。
