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Osmoregulatory active sodium‐glycerol co‐transport in the halotolerant yeast Debaryomyces hansenii
Author(s) -
Lucas Candida,
Da Costa M.,
Van Uden N.
Publication year - 1990
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.320060303
Subject(s) - sodium , glycerol , debaryomyces hansenii , symporter , halotolerance , potassium , electrochemical gradient , osmotic pressure , protonophore , chemistry , biochemistry , inorganic chemistry , chromatography , biology , yeast , membrane , salinity , organic chemistry , ecology , transporter , gene
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: V max , decreasing from over 500 to less than 40 μmol g −1 per h over a concentration range of 0–3 M extracellular sodium chloride; K m (glycerol) 0·40–0·6 m M over the same range; K m (sodium ions) 16·0 ± 3·21μ M ; K m , (potassium ions) 10·4 ± 3·6μ M . 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.