IN-VIVO ETHANOL-ACTIVATION OF THE PLASMA-MEMBRANE ATPASE OF PICHIA-STIPITIS - EFFECT OF THE CARBON SOURCE

The addition of ethanol during growth increased the plasma membrane AT Pase activity of Pichia stipitis. However, the level of stimulation, d ue to the addition of 10 g l(-1) ethanol, depended on the sugar used f or growth: whereas a 100% increase in ATPase activity was generated wi th glucose as carbon source, no significant increase was detected with xylose. Independently of ethanol, the activity of the ATPase from P. stipitis grown on glucose increased 2-fold compared to that from cells grown on xylose. The glucose effect and the ethanol effect were addit ive: the ethanol treated cells grown on glucose showing a 4-fold incre ase in ATPase activity compared to xylose grown cells. The in vivo ATP ase activation by either ethanol or glucose was related to an increase in V-max. Possible mechanisms for plasma membrane ATPase activation b y glucose-ethanol are discussed.