Contribution to the physiological characterization of glycerol active uptake in Saccharomycescerevisiae

Abstract

Evidence is presented here that in Saccharomyces cerevisiae IGC 3507, grown either on glycerol, ethanol or acetate, glycerol is transported by a high affinity uptake system of the electrogenic proton symport type, with Km of 1.7 +/- 0.7 mM, Vmax 441 +/- 19 micromolh(-1) g(-1) dry weight and a stoichiometry of 1:1 proton per molecule of glycerol, at 30 degrees C and pH 5.0. No competitors were found among other polyols and sugars. Glycerol maximum accumulation ratios followed p.m.f. with extracellular pH. CCCP prevented glycerol accumulation, and inhibited uptake. NaCl did not interfere with H+/glycerol kinetics and energetics. This transport system was shown to be under glucose repression and inactivation. Glucose-grown cells presented, instead, a lower affinity permease for glycerol, probably a facilitated diffusion. Growth on glucose in the presence of NaCl did not induce the high affinity carrier. The stringent control of cell physiological condition over induction suggests for glycerol proton symport rather a physiological role connected with growth under gluconeogenic conditions.

New insights on glycerol transport in Saccharomyces cerevisiae

“…This is in accordance with previously published results that show the active transport system to be under glucose repression [5,6]. When cells were collected during diauxic shift, W303-1A and gup1gup2 strains presented accumulation of radiolabelled glycerol against gradient, not measurable in the gup1gup2gut1 strain (Fig.…”

“…chromatography Carbon source consumption and metabolites present in the growth media were followed by high performance liquid chromatography according to Lages and Lucas [5].…”

“…Initial rates of glycerol uptake, external alkalinization upon glycerol addition, as well as in/out accumulation ratios, were determined as previously described [5,9,12,13]. The intracellular volume values used to determine intracellular glycerol molarity have been determined by Lages and Lucas [5].…”

“…The intracellular volume values used to determine intracellular glycerol molarity have been determined by Lages and Lucas [5].…”

“…Glycerol, the main compatible solute used by yeasts under low a w in high osmolarity environments [1], can permeate Saccharomyces cerevisiae plasma membrane through a constitutively expressed channel, Fps1p [2][3][4], and a H þ /symport, active in cells derepressed by growth on non-fermentable carbon sources [5]. This transport system was associated with the expression of the genes GUP1 and GUP2 [6].…”