Isogai Shota, Nishimura Akira, Inoue Akiko, Sonohara Shino, Tsugukuni Takashi, Takagi Hiroshi
Institute for Research Initiatives, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
Plant Bio Business Unit, Musashi Seimitsu Industry Co., Ltd., Toyohashi, Aichi, Japan.
Biosci Biotechnol Biochem. 2024 Dec 23;89(1):124-132. doi: 10.1093/bbb/zbae154.
Essential amino acids (EAAs) are important for the maintenance of brain functions. Therefore, the yeast Saccharomyces cerevisiae that accumulates EAAs would help elderly people ingest appropriate levels of EAAs, which in turn could slow neurodegeneration, extend the healthy lifespan, and improve quality of life. Here, we isolated 2 mutant strains, ETH-80 and ETH-129, that accumulate the EAA methionine. Both strains were derived from a diploid laboratory yeast by conventional mutagenesis and carry a novel mutation in the MET13 gene, which encodes the Ser443Phe variant of methylenetetrahydrofolate reductase. Enzymatic analysis revealed that the Ser443Phe substitution abolished the sensitivity to S-adenosyl methionine (SAM)-mediated inhibition even in the presence of 2 m m SAM, while increasing the activity for NADPH-dependent reduction. Furthermore, yeast cells expressing the Ser443Phe variant showed a 4-fold increase in intracellular methionine content compared to the wild-type Met13. These findings will be useful for the future development of methionine-accumulating yeast strains.
必需氨基酸（EAA）对维持脑功能很重要。因此，积累EAA的酿酒酵母（Saccharomyces cerevisiae）将有助于老年人摄入适量的EAA，这反过来可以减缓神经退行性变、延长健康寿命并提高生活质量。在此，我们分离出了2个积累EAA甲硫氨酸的突变菌株ETH-80和ETH-129。这两个菌株均通过传统诱变从二倍体实验室酵母衍生而来，并且在MET13基因中携带一个新突变，该基因编码亚甲基四氢叶酸还原酶的Ser443Phe变体。酶分析表明，即使在存在2 mM S-腺苷甲硫氨酸（SAM）的情况下，Ser443Phe取代也消除了对SAM介导的抑制的敏感性，同时增加了对NADPH依赖性还原的活性。此外，与野生型Met13相比，表达Ser443Phe变体的酵母细胞的细胞内甲硫氨酸含量增加了4倍。这些发现将有助于未来积累甲硫氨酸的酵母菌株的开发。
