Yang Xu, Meng Lu, Lin Xue, Jiang Huan-Yuan, Hu Xiao-Ping, Li Cong-Fa
College of Food Science and Engineering, Hainan University, Haikou, China.
Engineering Research Center of Utilization of Tropical Polysaccharide Resources, Ministry of Education, Haikou, China.
Front Microbiol. 2021 Jun 1;12:665261. doi: 10.3389/fmicb.2021.665261. eCollection 2021.
Glucose repression is a key regulatory system controlling the metabolism of non-glucose carbon source in yeast. Glucose represses the utilization of maltose, the most abundant fermentable sugar in lean dough and wort, thereby negatively affecting the fermentation efficiency and product quality of pasta products and beer. In this study, the focus was on the role of three kinases, Elm1, Tos3, and Sak1, in the maltose metabolism of baker's yeast in lean dough. The results suggested that the three kinases played different roles in the regulation of the maltose metabolism of baker's yeast with differential regulations on genes. Elm1 was necessary for the maltose metabolism of baker's yeast in maltose and maltose-glucose, and the overexpression of could enhance the maltose metabolism and lean dough fermentation ability by upregulating the transcription of ( is the locus) in maltose and maltose-glucose and in maltose. The native level of and was essential for yeast cells to adapt glucose repression, but the overexpression of and alone repressed the expression of in maltose-glucose and in maltose. Moreover, the three kinases might regulate the maltose metabolism via the Snf1-parallel pathways with a carbon source-dependent manner. These results, for the first time, suggested that Elm1, rather than Tos3 and Sak1, might be the dominant regulator in the maltose metabolism of baker's yeast. These findings provided knowledge about the glucose repression of maltose and gave a new perspective for breeding industrial yeasts with rapid maltose metabolism.
葡萄糖阻遏是控制酵母中非葡萄糖碳源代谢的关键调控系统。葡萄糖会抑制麦芽糖的利用，而麦芽糖是低糖面团和麦芽汁中含量最丰富的可发酵糖，从而对意大利面制品和啤酒的发酵效率及产品质量产生负面影响。在本研究中，重点关注了三种激酶Elm1、Tos3和Sak1在低糖面团中面包酵母麦芽糖代谢中的作用。结果表明，这三种激酶在面包酵母麦芽糖代谢调控中发挥不同作用，对基因有不同调控。Elm1对于面包酵母在麦芽糖和麦芽糖 - 葡萄糖中的麦芽糖代谢是必需的，其过表达可通过上调麦芽糖和麦芽糖 - 葡萄糖中（是基因座）以及麦芽糖中 的转录来增强麦芽糖代谢和低糖面团发酵能力。 和 的天然水平对于酵母细胞适应葡萄糖阻遏至关重要，但单独过表达 和 会抑制麦芽糖 - 葡萄糖中 和麦芽糖中 的表达。此外这三种激酶可能通过Snf1平行途径以碳源依赖的方式调节麦芽糖代谢。这些结果首次表明，Elm1而非Tos3和Sak1可能是面包酵母麦芽糖代谢中的主要调节因子。这些发现提供了关于麦芽糖葡萄糖阻遏的知识，并为培育具有快速麦芽糖代谢能力的工业酵母提供了新视角。
