Deletion of the ATH1 gene in Saccharomyces cerevisiae prevents growth on trehalose

The biological function of the yeast trehalases (EC 3.2.1.28) consists of down-regulation of the concentration of trehalose via glucose formation by trehalose hydrolysis. While it is generally accepted that the cytosolic neutral trehalase (encoded by the NTH1 gene) is responsible for trehalose hydrolysis in intact cells, very little is known about a role of the vacuolar acid trehalase and the product of the recently described neutral trehalase gene YBR0106 (NTH2). We have analyzed the role of the acid trehalase in trehalose hydrolysis using the ATH1 deletion mutant (Δathl) of Saccharomyces cerevisiae [M. Destruelle et al. (1995) Yeast 11, 1015–1025] deficient in acid trehalase activity under various nutritional conditions. In contrast to wild-type and a mutant deficient in the neutral trehalase (Δathl ), the Aathl mutant does not grow on trehalose as a carbon source. Experiments with diploid strains heterozygous for Δathl show a gene dosage effect for the ATH1 gene for growth on trehalose. The need for acid trehalase for growth on trehalose is supported by the finding that acid trehalase activity is induced during exponential growth of cells on trehalose while no such induction is measurable during growth on glucose. Our results show that the vacuolar acid trehalase Ath1p is necessary for the phenotype of growth on trehalose, i.e. trehalose utilization, in contrast to cytosolic neutral trehalase Nth1p which is necessary for intracellular degradation of trehalose. For explanation of the need for vacuolar acid trehalase and not cytosolic neutral trehalase for growth on trehalose, the participation of endocytosis for uptake of trehalose from medium to the vacuoles is discussed.