Zhu Jiangfeng, Shalel-Levanon Sagit, Bennett George, San Ka-Yiu
Department of Bioengineering, Rice University, Houston, Texas, USA.
Biotechnol Bioeng. 2007 May 1;97(1):138-43. doi: 10.1002/bit.21219.
The product of yfiD gene is similar to pyruvate formate-lyase (PFL) activase and it has been reported to activate PFL by replacing the glycyl radical domain. To quantitate the effect of YfiD on the cell metabolism in microaerobic cultures, glucose-limited chemostat cultures were conducted with Escherichia coli yfiD mutant and yfiDarcA mutant strains. The microaerobic condition was controlled by purging the culture media with 2.5% O(2) in N(2). The intracellular metabolic flux distributions in these cultures were estimated based on C-13 labeling experiments. By comparing with the flux distributions in wild-type E. coli and the arcA mutant, it was shown that YfiD contributes to about 18% of the PFL flux in the arcA mutant, but it did not contribute to the PFL flux in wild-type E. coli. It was also shown that the cell used both PFL and pyruvate dehydrogenase (PDH) to supplement the acetyl-coenzyme A (AcCoA) pool under microaerobic conditions. The flux through PDH was about 22-30% of the total flux toward AcCoA in the wild-type, the yfiD mutant and yfiDarcA mutant strains. Relatively higher lactate production was seen in the yfiDarcA mutant than the other strains, which was due to the lower total flux through PFL and PDH toward AcCoA in this strain.
yfiD基因的产物类似于丙酮酸甲酸裂解酶（PFL）激活酶，据报道它通过取代甘氨酰自由基结构域来激活PFL。为了定量YfiD在微需氧培养中对细胞代谢的影响，使用大肠杆菌yfiD突变体和yfiDarcA突变体菌株进行了葡萄糖限制恒化器培养。通过用含2.5% O₂的N₂吹扫培养基来控制微需氧条件。基于¹³C标记实验估计了这些培养物中的细胞内代谢通量分布。与野生型大肠杆菌和arcA突变体中的通量分布相比，结果表明YfiD对arcA突变体中约18%的PFL通量有贡献，但对野生型大肠杆菌中的PFL通量没有贡献。还表明在微需氧条件下，细胞同时使用PFL和丙酮酸脱氢酶（PDH）来补充乙酰辅酶A（AcCoA）库。在野生型、yfiD突变体和yfiDarcA突变体菌株中，通过PDH的通量约占通向AcCoA的总通量的22% - 30%。在yfiDarcA突变体中观察到的乳酸产量相对高于其他菌株，这是由于该菌株中通过PFL和PDH通向AcCoA的总通量较低。
