Sha Chong, Wang Qiang, Wang Hongcheng, Duan Yilan, Xu Chongmao, Wu Lian, Ma Kesen, Shao Weilan, Jiang Yu
Biofuels Institute, School of the Environment, Jiangsu University, Zhenjiang 212013, China.
School of Biological and Food Engineering, Suzhou University, Bianhe Middle Road 49, Suzhou 234000, China.
Biology (Basel). 2022 Sep 5;11(9):1318. doi: 10.3390/biology11091318.
Hyperthermophilic spp. are candidates for cellulosic ethanol fermentation. A bifunctional iron-acetaldehyde/alcohol dehydrogenase (Fe-AAdh) has been revealed to catalyze the acetyl-CoA (Ac-CoA) reduction to form ethanol via an acetaldehyde intermediate in (). In this organism, there are three additional alcohol dehydrogenases, Zn-Adh, Fe-Adh1, and Fe-Adh2, encoded by genes CTN_0257, CTN_1655, and CTN_1756, respectively. This paper reports the properties and functions of these enzymes in the fermentation pathway from Ac-CoA to ethanol. It was determined that Zn-Adh only exhibited activity when oxidizing ethanol to acetaldehyde, and no detectable activity for the reaction from acetaldehyde to ethanol. Fe-Adh1 had specific activities of approximately 0.7 and 0.4 U/mg for the forward and reverse reactions between acetaldehyde and ethanol at a pH of 8.5 and T of 95 °C. Catalyzing the reduction of acetaldehyde to produce ethanol, Fe-Adh2 exhibited the highest activity of approximately 3 U/mg at a pH of 7.0 and T of 85 °C, which were close to the optimal growth conditions. These results indicate that Fe-Adh2 and Zn-Adh are the main enzymes that catalyze ethanol formation and consumption in the hyperthermophilic bacterium, respectively.
嗜热菌是纤维素乙醇发酵的候选菌株。已发现一种双功能铁 - 乙醛/醇脱氢酶（Fe - AAdh）可催化乙酰辅酶A（Ac - CoA）还原，通过乙醛中间体生成乙醇（在……中）。在这种生物体中，还有另外三种醇脱氢酶，分别由基因CTN_0257、CTN_1655和CTN_1756编码，即Zn - Adh、Fe - Adh1和Fe - Adh2。本文报道了这些酶在从Ac - CoA到乙醇的发酵途径中的性质和功能。已确定Zn - Adh仅在将乙醇氧化为乙醛时表现出活性，而对于从乙醛到乙醇的反应没有可检测到的活性。在pH为8.5和温度为95℃时，Fe - Adh1对于乙醛和乙醇之间的正向和逆向反应的比活性分别约为0.7和0.4 U/mg。Fe - Adh2催化乙醛还原生成乙醇，在pH为7.0和温度为85℃时表现出最高活性，约为3 U/mg，这接近最佳生长条件。这些结果表明，Fe - Adh2和Zn - Adh分别是嗜热菌中催化乙醇形成和消耗的主要酶。
