S-methyl-methionine (SMM), also known as vitamin U, is an important food supplement produced by various plants. In this study, we attempted to produce it in an engineered microorganism, Saccharomyces cerevisiae, by introducing an MMT gene encoding a Methionine S-methyltransferase from Arabidopsis thaliana. The S. cerevisiae Sake K6 strain which is a Generally Recognized as Safe (GRAS) strain, was chosen as the host because it produces a significant amount of S-adenosylmethionine (SAM), a precursor of SMM. To increase SMM production in the host, MHT1 and SAM4 genes encoding Homocysteine S-methyltransferase were knocked out to prevent SMM degradation. Additionally, MMP1 which encodes S-methyl-methionine permease, was deleted to prevent SMM from being imported into the cell. Finally, ACS2 gene encoding acetyl-CoA synthase was overexpressed, and MLS1 gene encoding malate synthase was deleted to increase SAM availability. Using the engineered strain, 1.92 g/L of SMM was produced by fed-batch fermentation. One-Sentence Summary: Introducing a plant-derived MMT gene encoding methionine S-methyltransferase into engineered Saccharomyces cerevisiae sake K6 allowed microbial production of S-methyl-methionine (SMM).

中文翻译：

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使用工程酿酒酵母清酒 K6 生产 S-甲基-蛋氨酸

S-甲基甲硫氨酸（SMM），又称维生素U，是由多种植物产生的重要食品补充剂。在这项研究中，我们尝试通过引入来自拟南芥的编码蛋氨酸 S-甲基转移酶的 MMT 基因，在工程微生物酿酒酵母中生产它。酿酒酵母 Sake K6 菌株是公认安全的 (GRAS) 菌株，被选为宿主，因为它产生大量的 S-腺苷甲硫氨酸 (SAM)，SMM 的前体。为了增加宿主中 SMM 的产量，编码同型半胱氨酸 S-甲基转移酶的 MHT1 和 SAM4 基因被敲除，以防止 SMM 降解。此外，编码S-甲基甲硫氨酸通透酶的MMP1被删除，以防止SMM被输入细胞中。最后，编码乙酰辅酶A合酶的ACS2基因被过表达，编码苹果酸合酶的MLS1基因被删除以增加SAM的可用性。使用工程菌株，通过补料分批发酵生产了 1.92 g/L 的 SMM。一句话总结：将编码蛋氨酸 S-甲基转移酶的植物来源 MMT 基因引入工程酿酒酵母清酒 K6 中，允许微生物生产 S-甲基-蛋氨酸 (SMM)。