Uptake of Trehalose by Saccharomyces cerevisiae

Abstract

Trehalose, a storage sugar of baker''s yeast, is not metabolized when added to a cell suspension in water or a growth medium and to support growth only after a lag of about 10 h. It was transported into cells by at least 2 transport systems, the uptake being active, with a pH optimum at 5.5. There was no stoichiometry with the shift of protons into cells observed at high trehalose concentrations. Trehalose remained intact in cells and was not appreciably lost to a trehalose-free medium. The uptake systems were present directly after growth on glucose, then decayed with a half-life of about 25 min but could be reactivated by aerobic incubation with trehalose, maltose, .alpha.-methyl-D-glucoside, glucose or ethanol. The uptake systems thus induced were different as revealed by competition experiments. At least 1 of the systems for trehalose uptake showed cooperative kinetics. Comparative analysis with other disaccharides indicated the existence in S. cerevisiae, after induction with trehalose, of at least 4 systems for the uptake of .alpha.-methyl-D-glucoside, 4 systems for maltose, together with the 2 for trehalose, variously shared by the sugars, the total of .alpha.-glucoside-transporting systems being 5.