A protocol for Leuconostoc oelignos plasma membrane isolation, which was improved for studying lipidic and proteic constitution according to growth conditions, allowed us to determine some kinetic properties of membrane-bound ATPase activity: optimum pH, 5.6; the Michaelis constant (K m) for ATP, 1.1 mm; Mg2+-dependence. L. oelignos membrane-bound ATPase activity was regulated according to cell growth phase, growth medium and extracellular conditions. The regulation mode of this activity was not investigated but it was very rapid: differences in level of activity were observed in less than 1 h when extracellular pH was modified or when ethanol was added. Wine induced a large decrease in ATPase activity of L. oelignos. This may explain the loss of cell viability after direct inoculation into wine, when malolactic fermentation was not spontaneously obtained.