The gld1⁺ gene encoding glycerol dehydrogenase is required for glycerol metabolism in Schizosaccharomyces pombe

The budding yeast Saccharomyces cerevisiae is able to utilize glycerol as the sole carbon source via two pathways (glycerol 3-phosphate pathway and dihydroxyac-etone [DHA] pathway). In contrast, the fission yeast Schizosaccharomyces pombe does not grow on media containing glycerol as the sole carbon source. However, in the presence of other carbon sources such as galactose and ethanol, S. pombe could assimilate glycerol and glycerol was preferentially utilized over ethanol and galactose. No equivalent of S. cerevisiae Gcy1/glycerol dehydrogenase has been identified in S. pombe. However, we identified a gene in S. pombe, SPAC13F5.03c (gld1⁺), that is homologous to bacterial glycerol dehydrogenase. Deletion of gld1 caused a reduction in glycerol dehydrogenase activity and prevented glycerol assimilation. The gld1Δ cells grew on 50 mM DHA as the sole carbon source, indicating that the glycerol dehydrogenase encoded by gld1⁺ is essential for glycerol assimilation in S. pombe. Strains of S. pombe deleted for dak1⁺ and dak2⁺ encoding DHA kinases could not grow on glycerol and showed sensitivity to a higher concentration of DHA. The dak1Δ strain showed a more severe reduction of growth on glycerol and DHA than the dak2Δ strain because the expression of dak1⁺ mRNA was higher than that of dak2⁺. In wild-type S. pombe, expression of the gld1⁺, dak1⁺, and dak2⁺ genes was repressed at a high concentration of glucose and was derepressed during glucose starvation. We found that gld1⁺ was regulated by glucose repression and that it was derepressed in scr1Δ and tup12Δ strains.