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

Abstract

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 MAL genes. Elm1 was necessary for the maltose metabolism of baker’s yeast in maltose and maltose-glucose, and the overexpression of ELM1 could enhance the maltose metabolism and lean dough fermentation ability by upregulating the transcription of MALx1 (x is the locus) in maltose and maltose-glucose and MALx2 in maltose. The native level of TOS3 and SAK1 was essential for yeast cells to adapt glucose repression, but the overexpression of TOS3 and SAK1 alone repressed the expression of MALx1 in maltose-glucose and MALx2 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.

Mitochondrial phosphatidylethanolamine synthesis affects mitochondrial energy metabolism and quiescence entry through attenuation of Snf1/AMPK signaling in yeast

“…Therefore, we took advantage of depletion of Snf1‐activating kinase Sak1 43,45 . Budding yeast contains three upstream kinases, Sak1, Tos3, and Elm1, that are involved in Snf1 activation through phosphorylation of threonine 210 of Snf1 46 . Among these three kinases, Sak1 is the major one contributing to Snf1 activation 47 .…”

“…43,45 Budding yeast contains three upstream kinases, Sak1, Tos3, and Elm1, that are involved in Snf1 activation through phosphorylation of threonine 210 of Snf1. 46 Among these three kinases, Sak1 is the major one contributing to Snf1 activation. 47 Although sak1∆ and ups2∆sak1∆ cells grow similar to wild-type and ups2∆ ones in the log phase and can grow even in the post-diauxic shift phase (Figure S3), the Snf1 phosphorylation levels were greatly decreased in sak1∆ and ups2∆sak1∆ cells as compared to in wild-type and ups2∆ ones, respectively (Figure 4A).…”