Department of Bioscience, Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-Ku, Shizuoka 422-8259, Japan.
Department of Bioscience, Graduate School of Science and Technology, Shizuoka University, 836 Ohya, Suruga-Ku, Shizuoka 422-8259, Japan; Green Chemistry Research Division, Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Suruga-Ku, Shizuoka 422-8259, Japan.
J Biosci Bioeng. 2014 May;117(5):563-8. doi: 10.1016/j.jbiosc.2013.10.020. Epub 2013 Dec 4.
In Ashbya gossypii, isocitrate lyase (ICL1) is a very crucial enzyme for riboflavin production. Itaconate, the inhibitor of ICL1, has been used as an antimetabolite for mutagenic studies in A. gossypii. It has been reported that itaconate is produced from cis-aconitate by cis-aconitate decarboxylase (CAD1) in Aspergillus terreus. In this study, identification of CAD1 gene and determination of the presence of itaconate in the riboflavin biosynthetic pathway in A. gossypii were carried out to confirm itaconate metabolism. Although no CAD1 candidate gene was found and no itaconate production was observed, cis- and trans-aconitate were detected in the riboflavin production phase. It is known that trans-aconitate inhibits aconitase (ACO1) in the tricarboxylic acid cycle. In A. gossypii, the transcription level of AGR110Wp, the homolog of trans-aconitate 3-methyltransferase (TMT1), was enhanced by almost threefold during riboflavin production than that during its growth phase. TMT1 catalyzes the methylation reaction of trans-aconitate in Saccharomyces cerevisiae. Thus, these results suggest that the enhancement of the transcription level of this TMT1 homolog decreases the trans-aconitate level, which may mitigate the inhibition of ACO1 by oxidative stress in the riboflavin biosynthetic pathway in A. gossypii. This is a novel finding in A. gossypii, which may open new metabolic engineering ideas for improving riboflavin productivity.
在棉子糖棉铃菌中，异柠檬酸裂解酶（ICL1）是核黄素生产中非常关键的酶。衣康酸，ICL1 的抑制剂，已被用作诱变研究的抗代谢物在棉子糖棉铃菌中。据报道，衣康酸是由土曲霉中的顺乌头酸顺式脱羧酶（CAD1）从顺乌头酸产生的。在这项研究中，鉴定了 CAD1 基因，并确定了棉子糖棉铃菌核黄素生物合成途径中衣康酸的存在，以确认衣康酸代谢。虽然没有找到 CAD1 候选基因，也没有观察到衣康酸的产生，但在核黄素生产阶段检测到顺式和反式乌头酸。已知反式乌头酸抑制三羧酸循环中的顺乌头酸酶（ACO1）。在棉子糖棉铃菌中，其同源物反式乌头酸 3-甲基转移酶（TMT1）的转录水平在核黄素生产阶段比生长阶段提高了近三倍。TMT1 在酿酒酵母中催化反式乌头酸的甲基化反应。因此，这些结果表明，这种 TMT1 同源物转录水平的提高降低了反式乌头酸的水平，这可能减轻了核黄素生物合成途径中氧化应激对 ACO1 的抑制作用。这是在棉子糖棉铃菌中发现的一个新发现，可能为提高核黄素生产力开辟新的代谢工程思路。
