The plasma membrane ATPase of Kloeckera apiculata: purification, characterization and effect of ethanol on activity

Partially (6-fold) purified plasma membrane ATPase from an ethanol-sensitive yeast, Kloeckera apiculata, had an optimum pH of 6.0, an optimum temperature of 35°C, a K m of 3.6 mM ATP and a V max of 11 μmol Pi/min.mg protein. SDS-PAGE of the semi-purified plasma membrane showed a major band of 106 kDa. No in vivo activation of the ATPase by glucose was observed. Although 4% (v/v) ethanol decreased the growth rate by 50% it did not affect the ATPase. Concentrations of ethanol ≥2% (v/v) did, however, inhibit the enzyme in vitro. The characteristics of the enzyme did not change during growth in the presence of ethanol.