Role of Elm1, Tos3, and Sak1 Protein Kinases in the Maltose Metabolism of Baker's Yeast.

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.