Under aerobic conditions, S. cerevisiae are able to utilize glycerol as a sole carbon and energy source. Glycerol degradation, shown here, is a two-step process mediated by the gene products of GUT1 and GUT2. GUT1 encodes a glycerol kinase that converts glycerol to glycerol-3-phosphate in the cytosol. The product of this reaction is transported to the mitochondria where it is oxidized to dihydroxyacetone by the membrane protein Gut2p, a glycerol-3-phosphate dehydrogenase. Dihydroxyacetone is then transported back to the cytosol where it enters into either glycolysis or gluconeogenesis (4, 2, 5).

GUT1 gene expression is carbon source regulated; transcription is repressed when cells are grown on fermentable carbon sources such as glucose and induced on non-fermentable carbon sources such as glycerol or ethanol (4, 3, 6). On non-fermentable carbon sources, GUT1 transcription is upregulated by the transcriptional activators Adr1p, Ino2p, and Ino4p (3). Conversely, the negative regulator Opi1p facilitates GUT1 repression (3, 6).

Mutations in the human glycerol kinase homolog of Gut1p are linked to the disease hyperglycerolemia (OMIM; 7). Of the three clinical forms of this disease, infantile, juvenile, and adult, the infantile and juvenile forms are the most severe with symptoms including elevated levels of glycerol, growth retardation, psychomotor retardation, osteoporosis, and adrenal hypoplasia (reviewed in 8).

Last updated: 2006-02-17