Abstract: Lipoamide dehydrogenase encoded by lpdA gene is the subunit of pyruvate dehydrogenase complex,α-ketoglutarate dehydrogenase complex and glycine cleavage multi-enzyme systems. In the present study, the comparison of the fermentative properties between lpdA knockout E. coli and the wild type was made with different carbon sources and aeration conditions. Furthermore, the effect of lpdA gene knockout on the metabolism of E. coli was studied based on the measurement of some key enzyme activities and the intracellular metabolite concentrations. The results showed that under aerobic condition, using glucose as a carbon source, the knockout of lpdA gene led to the accumulation of pyruvate, D-lactate and L-glutamate; the repression of the TCA cycle; the activation of the glyoxylate shunt and the glucose-6-phosphate dehydrogenase in the oxidative pentose phosphate pathway. These conclusions were reinforced by the fermentation using acetate or pyruvate as a carbon source under aerobic condition and the fermentation using glucose as a carbon source under microaerobic condition.

摘要： lpdA基因编码的lipoamide dehydrogenase是丙酮酸脱氢酶复合体、α-酮戊二酸脱氢酶复合体和甘氨酸裂解多酶体系的组成亚基之一.比较了不同碳源及通气条件下，lpdA基因敲除突变E. coli与野生E. coli的发酵特性，并通过对一些主要的酶活和胞内代谢产物浓度的测量，考察了lpdA基因敲除对E. coli代谢的影响.结果表明：葡萄糖为碳源的有氧条件下，lpdA基因的敲除导致丙酮酸、D-乳酸、L-谷氨酸的积累，TCA循环的抑制，乙醛酸途径和磷酸戊糖途径中的磷酸葡萄糖脱氢酶的激活.乙酸或丙酮酸为碳源的有氧发酵及葡萄糖为碳源的微氧发酵实验补充了以上的结论.