Kobayashi Keiichi, Hattori Takasumi, Hayashi Rie, Kirimura Kohtaro
a Faculty of Science and Engineering, Department of Applied Chemistry , Waseda University , Shinjuku-ku , Japan.
Biosci Biotechnol Biochem. 2014;78(7):1246-53. doi: 10.1080/09168451.2014.918483. Epub 2014 Jun 17.
In the tricarboxylic acid (TCA) cycle, NADP(+)-specific isocitrate dehydrogenase (NADP(+)-ICDH) catalyzes oxidative decarboxylation of isocitric acid to form α-ketoglutaric acid with NADP(+) as a cofactor. We constructed an NADP(+)-ICDH gene (icdA)-overexpressing strain (OPI-1) using Aspergillus niger WU-2223L as a host and examined the effects of increase in NADP(+)-ICDH activity on citric acid production. Under citric acid-producing conditions with glucose as the carbon source, the amounts of citric acid produced and glucose consumed by OPI-1 for the 12-d cultivation period decreased by 18.7 and 10.5%, respectively, compared with those by WU-2223L. These results indicate that the amount of citric acid produced by A. niger can be altered with the NADP(+)-ICDH activity. Therefore, NADP(+)-ICDH is an important regulator of citric acid production in the TCA cycle of A. niger. Thus, we propose that the icdA gene is a potentially valuable tool for modulating citric acid production by metabolic engineering.
在三羧酸（TCA）循环中，NADP（+）特异性异柠檬酸脱氢酶（NADP（+）-ICDH）催化异柠檬酸的氧化脱羧反应，以NADP（+）作为辅因子形成α-酮戊二酸。我们以黑曲霉WU-2223L为宿主构建了一个过表达NADP（+）-ICDH基因（icdA）的菌株（OPI-1），并研究了NADP（+）-ICDH活性增加对柠檬酸产生的影响。在以葡萄糖为碳源的柠檬酸生产条件下，与WU-2223L相比，OPI-1在12天培养期内产生的柠檬酸量和消耗的葡萄糖量分别减少了18.7%和10.5%。这些结果表明，黑曲霉产生的柠檬酸量可随NADP（+）-ICDH活性而改变。因此，NADP（+）-ICDH是黑曲霉TCA循环中柠檬酸产生的重要调节因子。因此，我们认为icdA基因是通过代谢工程调节柠檬酸产生的潜在有价值工具。
