Branched-chain amino acids (BCAAs) play an important role in lipid metabolism by serving as signal molecules as well as a potential acetyl-CoA source. Our previous study found that in the oleaginous fungus Mucor circinelloides, beta-isopropylmalate dehydrogenase (IPMDH), an important enzyme participating in the key BCAA leucine biosynthesis, was differentially expressed during lipid accumulation phase and has a positive role on lipogenesis. To further analyze its effects on lipogenesis in another oleaginous fungus Mortierella alpina, the IPMDH-encoding gene MaLeuB was homologously expressed. It was found that the total fatty acid content in the recombinant strain was increased by 20.2% compared with the control strain, which correlated with a 4-fold increase in the MaLeuB transcriptional level. Intracellular metabolites analysis revealed significant changes in amino acid biosynthesis and metabolism, tricarboxylic acid cycle and butanoate metabolism; specifically, leucine and isoleucine levels were upregulated by 6.4-fold and 2.2-fold, respectively. Our genetic engineering approach and metabolomics study demonstrated that MaLeuB is involved in fatty acid metabolism in M. alpina by affecting BCAAs metabolism, and this newly discovered role of IPMDH provides a potential bypass route to increase lipogenesis in oleaginous fungi.

支链氨基酸 (BCAA) 作为信号分子和潜在的乙酰辅酶 A 来源在脂质代谢中发挥重要作用。我们之前的研究发现，在产油真菌圆环毛霉中，β-异丙基苹果酸脱氢酶 (IPMDH) 是一种参与关键 BCAA 亮氨酸生物合成的重要酶，在脂质积累阶段差异表达，对脂肪生成具有积极作用。进一步分析其对另一种产油真菌高山被孢霉（Mortierella alpina）脂肪生成的影响，IPMDH编码基因MaLeuB被同源表达。结果发现，与对照菌株相比，重组菌株中的总脂肪酸含量增加了 20.2%，这与MaLeuB转录水平增加了 4 倍相关。细胞内代谢物分析显示氨基酸生物合成和代谢、三羧酸循环和丁酸代谢发生显着变化；具体而言，亮氨酸和异亮氨酸水平分别上调了 6.4 倍和 2.2 倍。我们的基因工程方法和代谢组学研究表明，MaLeuB参与脂肪酸代谢的高山被孢霉 通过影响支链氨基酸的代谢，IPMDH 的这种新发现的作用为增加产油真菌的脂肪生成提供了潜在的旁路途径。