Relationship Between Effect of Ethanol on Proton Flux Across Plasma Membrane and Ethanol Tolerance, inPichia stipitis

Autor: Meyrial, V., Delgenes, J.-P., Davison, J., Salmon, J.-M., Moletta, R., Gounot, A.-M.
Zdroj: Anaerobe; December 1997, Vol. 3 Issue: 6 p423-429, 7p
Abstrakt: Pichia stipitisefficiently converts glucose or xylose into ethanol but is inhibited by ethanol concentrations exceeding 30 g/L. InSaccharomyces cerevisiae, ethanol has been shown to alter the movement of protons into and out of the cell. InP. stipitisthe passive entry of protons into either glucose- or xylose-grown cells is unaffected at physiological ethanol concentrations. In contrast, active proton extrusion is affected differentially by ethanol, depending on the carbon source catabolized. In fact, in glucose-grown cells, the H+-extrusion rate is reduced by low ethanol concentrations, whereas, in xylose-grown cells, the H+-extrusion rate is reduced only at non-physiological ethanol concentrations. Thus, the ethanol inhibitory effect on growth and ethanol production, in glucose-grown cells, is probably caused by a reduction in H+-extrusion. Comparison of the rates of H+-flux with the relatedin vitroH+-ATPase activity suggests a new mechanism for the regulation of the proton pumping plasma membrane ATPase (EC 3.6.1.3) ofP. stipitis, by both glucose and ethanol. Glucose activates both the ATP hydrolysis and the proton-pumping activities of the H+-ATPase, whereas ethanol causes an uncoupling between the ATP hydrolysis and the proton-pumping activities. This uncoupling may well be the cause of ethanol induced growth inhibition of glucose grownP. stipitiscells.
Databáze: Supplemental Index
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