Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211800, China; College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211800, China.
School of Pharmaceutical Sciences, Nanjing Tech University, Nanjing 211800, China.
J Proteomics. 2018 May 15;179:140-149. doi: 10.1016/j.jprot.2018.03.014. Epub 2018 Mar 20.
Arachidonic acid (ARA) is a valuable polyunsaturated fatty acid produced by Mortierella alpina. Although some strategies such as nitrogen supplementation have shown the potential to affect the aging of M. alpina in ways which enable it to produce more ARA, the underlying mechanism remains elusive. Herein, we conducted a systematical analysis of the lipid droplet proteome, as well as the whole-cell proteome and metabolome, in order to elucidate how and why two different nitrogen sources (KNO and urea) affect the aging of M. alpina and the corresponding ARA concentration. We found that KNO promoted the ARA concentration, while urea accelerated lipid consumption and stimulated the decomposition of mycelia. Although both KNO and urea activated carbohydrate metabolic pathways, KNO exerted a stronger promoting effect on the pentose phosphate pathway and induced the lipid droplets to participate in the citrate-pyruvate cycle. The activities of malic enzyme and isocitrate dehydrogenase were also promoted more by KNO. These pathways provided additional substrates and reducing power for ARA synthesis and ROS elimination. Accordingly, since urea showed a weaker promotion of the related pathways, it caused a depression of the antioxidant system and a consequent increase of ROS. These findings facilitate the design of nitrogen supplementation strategies to achieve higher ARA concentrations, and provide guidance for deciphering the mechanisms of similar aging phenomena in other oleaginous microorganisms.
Polyunsaturated fatty acids such as arachidonic acid (ARA) are valuable nutrients, which play important roles in preventing numerous diseases and facilitating development. Although it has been found for years that ARA production will be increased in the aging process of Mortierella alpina (M. alpina) and nitrogen sources are involved in this process, the underlying mechanism for this phenomenon remains unknown. In this work, we used the subcellular proteomics, whole-cell proteomics and metabolomics methods to explore the mechanisms by which two different nitrogen (KNO and urea) affected the aging process of M. alpina. Finally, we gave some new insights for the mechanisms mentioned above. This finding will fuel the technology developments for the ARA production using microbes.
花生四烯酸（ARA）是一种有价值的多不饱和脂肪酸，由高山被孢霉（Mortierella alpina）产生。尽管一些策略，如氮源补充，已经显示出影响高山被孢霉老化的潜力，使其能够产生更多的 ARA，但潜在的机制仍然难以捉摸。在此，我们进行了系统的脂滴蛋白质组学、全细胞蛋白质组学和代谢组学分析，以阐明两种不同氮源（KNO 和尿素）如何以及为何影响高山被孢霉的老化及其相应的 ARA 浓度。我们发现 KNO 促进了 ARA 浓度的增加，而尿素则加速了脂质的消耗，并刺激了菌丝的分解。尽管 KNO 和尿素都激活了碳水化合物代谢途径，但 KNO 对戊糖磷酸途径的促进作用更强，并诱导脂滴参与柠檬酸-丙酮酸循环。苹果酸酶和异柠檬酸脱氢酶的活性也更受 KNO 的促进。这些途径为 ARA 合成和 ROS 消除提供了额外的底物和还原力。因此，由于尿素对相关途径的促进作用较弱，它会导致抗氧化系统的抑制和 ROS 的增加。这些发现有助于设计氮源补充策略以实现更高的 ARA 浓度，并为破译其他油脂微生物中类似老化现象的机制提供指导。
多不饱和脂肪酸，如花生四烯酸（ARA），是有价值的营养物质，在预防许多疾病和促进发育方面发挥着重要作用。虽然多年来已经发现 ARA 的产生会在高山被孢霉（M. alpina）的老化过程中增加，并且氮源参与了这一过程，但这一现象的潜在机制仍不清楚。在这项工作中，我们使用亚细胞蛋白质组学、全细胞蛋白质组学和代谢组学方法来探索两种不同氮源（KNO 和尿素）如何影响高山被孢霉老化过程的机制。最后，我们对上述机制提出了一些新的见解。这一发现将为利用微生物生产 ARA 的技术发展提供动力。
