Dürre P, Fischer R J, Kuhn A, Lorenz K, Schreiber W, Stürzenhofecker B, Ullmann S, Winzer K, Sauer U
Institut für Mikrobiologie, Georg-August-Universität Göttingen, Germany.
FEMS Microbiol Rev. 1995 Oct;17(3):251-62. doi: 10.1111/j.1574-6976.1995.tb00209.x.
The enzymes acetoacetate decarboxylase and coenzyme A transferase catalyse acetone production from acetoacetyl-CoA in Clostridium acetobutylicum. The adc gene encoding the former enzyme is organized in a monocistronic operon, while the ctf genes form a common transcription unit with the gene (adhE) encoding a probable polyfunctional aldehyde/alcohol dehydrogenase. This genetic arrangement could reflect physiological requirements at the onset of solventogenesis. In addition to AdhE, two butanol dehydrogenase isozymes and a thiolase are involved in butanol synthesis. RNA analyses showed a sequential order of induction for the different butanol dehydrogenase genes, indicating an in vivo function of BdhI in low level butanol formation. The physiological roles of AdhE and BdhII most likely involve high level butanol formation, with AdhE being responsible for the onset of solventogenesis and BdhII ensuring continued butanol production. Addition of methyl viologen results in artificially induced butanol synthesis which seems to be mediated by a still unknown set of enzymes. Although the signal that triggers the shift to solventogenesis has not yet been elucidated, recent investigations suggest a possible function of DNA supercoiling as a transcriptional sensor of the respective environmental stimuli.
在丙酮丁醇梭菌中，乙酰乙酸脱羧酶和辅酶A转移酶催化由乙酰乙酰辅酶A生成丙酮。编码前一种酶的adc基因以单顺反子操纵子的形式组织，而ctf基因与编码一种可能的多功能醛/醇脱氢酶的基因（adhE）形成一个共同的转录单元。这种基因排列可能反映了溶剂生成开始时的生理需求。除了AdhE外，两种丁醇脱氢酶同工酶和一种硫解酶参与丁醇合成。RNA分析显示不同丁醇脱氢酶基因的诱导顺序是连续的，这表明BdhI在低水平丁醇形成中具有体内功能。AdhE和BdhII的生理作用很可能涉及高水平丁醇的形成，AdhE负责溶剂生成的开始，而BdhII确保丁醇的持续产生。添加甲基紫精会导致人工诱导的丁醇合成，这似乎是由一组仍未知的酶介导的。尽管尚未阐明触发向溶剂生成转变的信号，但最近的研究表明DNA超螺旋可能作为相应环境刺激的转录传感器发挥作用。
