Osmoregulatory active sodium‐glycerol co‐transport in the halotolerant yeast Debaryomyces hansenii

Abstract

Several authors have shown that the halotolerant yeast Debaryomyces hansenii, when growing exponentially in glucose medium in the presence of sodium chloride, maintains osmotic balance by establishing sodium and glycerol gradients of opposite signs across the plasma membrane. Evidence is presented here that the two gradients are linked through a sodium‐glycerol symport that uses the sodium gradient as a driving force for maintaining the glycerol gradient. The symporter also accepts potassium ions as co‐substrate. The kinetic parameters at 25°C, pH 5·0 were the following: Vmax, decreasing from over 500 to less than 40 μmol g−1 per h over a concentration range of 0–3 M extracellular sodium chloride; Km (glycerol) 0·40–0·6 mM over the same range; Km (sodium ions) 16·0 ± 3·21μM; Km, (potassium ions) 10·4 ± 3·6μM. Furthermore, it was observed that glycerol uptake was accompanied by proton uptake when extracellular sodium chloride was present and that the protonophore carbonylcyanide‐M‐chlorophenylhydrazone induced collapse of the glycerol gradient, supporting earlier proposals by others that the sodium gradient is maintained by an active sodium‐proton exchange mechanism.

The water relations of growth and polyhydroxy alcohol production by ascomycetous yeasts

“…The ability of some strains and species to tolerate higher NaCl concentrations could be due to the presence of a sodium extrusion pump (Hobot & Jennings, 1981;Norkrans & Kylin, 1969). Some yeasts evidently transport glycerol into their cells with sodium ions (Lucas et al, 1990;), yet may not possess an efficient mechanism to expel sodium ions.…”

“…hansenii (Adler et al, 1985;Lucas et al, 1990) and 2. rouxii which enable glycerol to be accumulated intracellularly up to 5000-fold. Furthermore, the greater retention of glycerol as observed here when the a, was adjusted with NaCl than with glucose could be related to the use of a sodium gradient as the driving force to maintain the glycerol gradient.…”

Characterization of glycerol uptake in bloodstream and procyclic forms of Trypanosoma brucei

“…During the last few years several studies dealing with glycerol transport mediated by membrane proteins have been published and it has been shown that glycerol can be taken up by the various transport systems present in eukaryotic cells, including facilitated diffusion [7], proton symport [8] and sodium symport [9]. Protein-facilitated glycerol uptake has been described for higher eukaryotic cells such as rat hepatocytes [10] and for microorganisms such as Neurospora crassa [11] and Streptomyces clavuligerus [12].…”

Use of Glycerol in Biotechnological Applications

“…Abbreviations: 1,3-PG 1,3-phosphoglycerate, DHA dihydroxyacetone, DhaK ATP dependent dihydroxyacetone kinase, DhaKLM PEP dependent dihydroxyacetone kinase, DHAP dihydroxyacetone-phosphate, F1,6BP fructose-1,6-bisphosphate, G3P glycerol-3-phosphate, G6P glucose-6-phosphate, GAP glyceraldehyde-3-phosphate, GAPDH glyceraldehyde-3-phosphate dehydrogenase, GldA soluble glycerol dehydrogenase, GldH membrane bound glycerol dehydrogenase, GlpABC quinone dependent glycerol-3-phosphate dehydrogenase, GlpF glycerol facilitator, GlpK glycerol kinase, GlpD glycerol-3-phosphate dehydrogenase, Gly glycerol, PEP phosphoenolpyruvate, P i inorganic phosphate, PPP pentose phosphate pathway, Pyr pyruvate, TCA tricarboxylic acid cycle, TPI triosephosphate isomerase. described in yeasts, such as sodium dependent symport for Debaryomyces hansenii (Lucas et al, 1990) and proton dependent symport for Pichia sorbitophila (Lages & Lucas, 1995) and Saccharomyces cerevisiae (Lages & Lucas, 1997, Ferreira et al, 2005. In yeasts, active glycerol transport is mostly regarded of importance with respect to the use of glycerol as an osmolyte under osmotic stress conditions.…”